Integrated effects of organic amendments and microbial inoculants on soil quality and wheat growth performance

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To explore the effects of different carbon sources and microbial inoculants on wheat growth and soil improvement, a two-factor randomized block design experiment was conducted with conventional fertilization as the control (CK). The pot experiment involved co-application of conventional fertilization with different organic materials (wheat straw (WS), maize straw (MS), and biochar (BC)) and various concentrations of microbial inoculant (0, 2.50, 5.00, 7.50, and 10.00 ml per pot). The results showed that compared to CK, the total nitrogen, available phosphorus, and shoot total nitrogen content in wheat were significantly increased by 65.48%, 34.17%, and 61.51%, respectively, under the BC3 treatment (conventional fertilizer + 31.61 g of biochar + 5.00 ml of bacillus subtilis bacillus). The available potassium, phosphorus, potassium, and bacterial count in roots were significantly increased by 121.50%, 68.60%, 101.89%, and 266.27%, respectively, under the BC5 treatment (conventional fertilizer + 31.61 g of biochar + 10.00 ml of bacillus subtilis bacterial agent). According to the effectiveness results of different combinations, it was found that BC3 treatment achieved the highest score. In addition, the results of structural equation modeling indicated that different carbon sources and microbial inoculants formulations indirectly affected wheat growth by regulating the soil microbial community and the soil physiochemical properties. In conclusion, biochar with microbial inoculants was found to be the most effective in enhancing wheat growth and synergistically improving soil physiochemical properties. biochar straw microbial inoculants wheat growth soil improvement Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1 Introduction The increasing global population and ongoing economic development have led to a steady rise in food demand. As a foundation of agricultural production, soil quality is critical for maintaining stable and enhanced crop yields. Improved soil conditions enhance crop resistance to pests and diseases, thereby minimizing the need for chemical fertilizers and pesticides and promoting sustainable agricultural development[ 1 ]. Healthy soil enhances root growth and nutrient uptake, supporting high crop yields under different climatic and environmental conditions, and contributing to national food security. Fertilizers play a vital role by supplying essential nutrients to boost yields. However, excessive long-term use of chemical fertilizers has led to soil degradation and environmental pollution, complicating their role in sustainable food production[ 2 ]. The long-term over-application of chemical fertilizers alter soil physiochemical properties, particularly pH, nutrient balance and organic matter content. This imbalance can cause micronutrient excesses or deficiencies and suppress soil microbial diversity and activity, ultimately reducing soil fertility. Over-reliance on chemical fertilizers further exacerbates soil degradation and but nutrient imbalances in the soil that affect crop growth and quality[ 3 ]. The drive for increased food production, coupled with excessive fertilization and irrational farming practices, has significantly degraded soil quality amid ongoing agricultural modernization[ 4 ]. These issues have diminished the soil fertility and accelerated degradation, becoming major constraints to food production and sustainable agricultural development. Declining arable land quality limits crop growth, reducing yield and quality, and significantly hinders the sustainable development of regional agriculture, especially in areas with intensive production[ 5 ]. Degradation of arable land quality not only hinders the improvement of agricultural productivity, but also threatens the stability of agro-ecosystems, intensifying challenges to sustainable agriculture. Addressing this requires a shift toward more scientific and sustainable management practices. Promoting green agriculture, enhancing soil remediation, adopting eco-agricultural technologies, and reducing dependence on chemical inputs are essential for restoring soil ecological functions and ensuring long-term agricultural sustainability[ 6 ]. Therefore, contemporary agricultural research focuses on improving soil quality and fostering the sustainable agriculture while augmenting food production. In this context, researchers are actively exploring alternative fertilization strategies, with growing attention on the combined use of straw return, biochar, and microbial inoculants. “Returning straw” refers to the process, of returning the remaining to incorporate the straw back into the soil after the crop harvest. This practice not only increase soil fertility and improves soil structure effectively, but also reduce the soil hazards associated with excessive application of chemical fertilizers[ 7 ]. Biochar is a highly aromatic, nitrogen-rich carbonaceous material produced by high-temperature pyrolysis under anoxic or low-oxygen condition[ 8 ]. Biochar can adsorb harmful substances and heavy metals in the soil, improve soil structure and increase soil fertility, maintaining a positive soil environment for crop growth[ 9 ]. Microbial inoculants are live beneficial microorganisms that are produced by industrialized expansion and processing. The microbial inoculants have a significant impact on agricultural production, improving soil health and crop yields, and effectively reducing reliance on chemical fertilizers and pesticides, thereby promoting sustainable agricultural development[ 10 ]. Although individual applications of straw, biochar and microbial inoculants are effective in enhancing the quality of cropland and boosting agricultural production, the research indicates that the combination of these applications is more effective in increasing crop yields and soil improvement than individual applications[ 11 ]. In addition, the combination of fertilizers can balance the nutrients in the soil, avoiding the problems of over-application and environmental pollution. The optimized combination of different organic matter components, it can improve the efficiency of nutrient absorption by crops, reduce the waste of fertilizers, reduce the risk of pollution of water sources and soil, and consequently augment the yield and quality of crops[ 12 ]. Therefore, the rational use of straw and biochar can improve the physical structure of soil, increase soil organic matter, and improve the water retention capacity and permeability of soil, while microbial inoculants can promote the propagation of soil microorganisms, enhance the biological activity of soil, and the efficiency of nutrient recycling[ 13 ]. In this study, we investigated the effect of different organic materials with microbial inoculants on the growth and development of wheat in greenhouse. This study aims to identify the best combination of organic materials and microbial inoculants, analyze their effects on the growth, yield and quality of wheat, and explore the optimization of soil fertility, nutrient cycling and microbial community structure. 2 Materials and methods 2.1 Experimental materials The experimental soil was collected from the field of Beishao Village, Dingzhou City, Hebei Province, China (38°23′44.39″N, 115°5′8.76″E). The soil has a pH of 7.72, which is close to neutral and suitable for most plants, with positive nutrient availability. The experiment was conducted in a light-controlled chamber of the west campus of Hebei Agricultural University (115.45°E, 38.82°N). The wheat plants (Gaoyou No. 1) were sown in the plastic flowerpot (16 cm in diameter and 17 cm in height). The test tissues were wheat straw (WS), maize straw (MS), biochar (BC), and Bacillus subtilis bacterial agent (screened for silage fermentation feed, with a bacterial content of 1.0×10 10 CFU/g). The conventional fertilizer applied was Huaxin compound fertilizer (N-P 2 O 5 -K 2 O, 24-6-10), purchased from Shanxi Huaxin Fertilizer Co. The basic physicochemical properties were as: organic matter content of 9.96 g/kg, which contributes to the maintenance of soil fertility and microbial activity. The total nitrogen content of 0.89 g/kg is moderately low and may require supplemental nitrogen fertilizer for proper crop growth. The available phosphorus content was 11.06 mg/kg, which was more adequate and could support the phosphorus nutritional requirements of plants. The available potassium content was 83.17 mg/kg, which was favorable to the healthy growth and resistance of the crop. Overall, the nutrient profile of this soil is relatively balanced, but the nitrogen content is slightly deficient, requiring proper fertilization according to crop needs. The test materials used in this experiment was biochar, wheat straw, and maize straw and their respective properties were as follows: Biochar contained 369.28 g/kg organic carbon, 5.04 g/kg total nitrogen, 1.85 g/kg total phosphorus, 32.19 g/kg total potassium, and had a pH of 7.63. Wheat straw had 389.14 g/kg organic carbon, 4.11 g/kg total nitrogen, 0.70 g/kg total phosphorus, 16.82 g/kg total potassium, and a pH of 6.74. Maize straw contained 404.44 g/kg organic carbon, 9.51 g/kg total nitrogen, 1.28 g/kg total phosphorus, 12.58 g/kg total potassium, and a pH of 7.40. 2.2 Experimental design The trial was conducted from August 1, 2023 to September 27, 2023. The experiment was a completely randomized experimental design with three material treatments (wheat straw, maize straw, and biochar) and five microbial inoculants concentrations (0 ml (0%), 2.50 ml (25%), 5.00 ml (50%), 7.50 ml (75%)), and 10.00 ml (100%) per pot). A control treatment (conventional fertilization without straw or microbial inoculants) was included, resulting in a total of 16 treatments. Each treatment was replicated four times, for a total of 64 pots. Plastic pots (16 cm diameter × 17 cm height) were filled with 2 kg of sieved soil. The nutrients were uniformly mixed in soil prior to the potting. The 10 seeds per pot at a depth of 2 cm were sown on August 1 st , 2023. After germination, seedlings were thinned to three per pot. Pots were repositioned weekly to minimize positional bias. Soil moisture was maintained at 70% of field capacity using the weighing method. Throughout the experiment, light intensity was maintained at 9000 Lux with a 14-hour photoperiod (6:00–20:00), room temperature was kept at 25–27°C, and relative humidity ranged from 44–55%. The experimental treatments are summarized in Table 1 . Table 1 Experimental design Crop plant Processing number Treatments Carbon sources (g/pot) Wheat CK Routine fertilization 0 WS1 Conventional fertilization + wheat straw Wheat straw 30 WS2 Conventional fertilizer + wheat straw + bacillus subtilis bacteriophage 25% (2.50 ml) Wheat straw 30 WS3 Conventional fertilizer + wheat straw + bacillus subtilis bacteriophage 50% (5.00 ml) Wheat straw 30 WS4 Conventional fertilizer + wheat straw + bacillus subtilis bacteriophage 75% (7.50 ml) Wheat straw 30 WS5 Conventional fertilization + wheat straw + bacillus subtilis bacteriophage 100% (10.00 ml) Wheat straw 30 MS1 Conventional fertilization + maize straw Maize straw 28.87 MS2 Conventional fertilizer + maize straw + bacillus subtilis bacteriophage 25% (2.5 ml) Maize straw 28.87 MS3 Conventional fertilizer + maize straw + bacillus subtilis bacteriophage 50% (5.00 ml) Maize straw28.87 MS4 Conventional fertilizer + maize straw + bacillus subtilis bacteriophage 75% (7.50 ml) Maize straw28.87 MS5 Conventional fertilization + maize straw + bacillus subtilis bacteriophage 100% (10.00 ml) Maize straw 28.87 BC1 Conventional fertilization + biochar Biochar 31.61 BC2 Conventional fertilization + biochar + bacillus subtilis bacteriophage 25% (2.50 ml) Biochar 31.61 BC3 Conventional fertilization + biochar + bacillus subtilis bacteriophage 50% (5.00 ml) Biochar 31.61 BC4 Conventional fertilizer + biochar + bacillus subtilis bacteriophage 75% (7.50 ml) Biochar 31.61 BC5 Conventional fertilization + biochar + bacillus subtilis bacteriophage 100% (10.00 ml) Biochar 31.61 Note: The determination of fertilizer amount is based on the principle of keeping the total carbon content in the basic index of the tested material consistent. 2.3 Assessment indices and methodologies The shoot part the plant height was measured with a tape measure from the soil surface to the apex. Stem diameter was determined 1.0 cm above the soil surface using a digital vernier caliper. The leaf surface area was measured by selecting three uniform leaves and the average value was taken as the leaf surface area of the plant. Chlorophyll content was measured from three-points (upper, middle, and lower portion) of fully expanded leaf of three wheat plants using a portable SPAD-502 chlorophyll meter. The average value recorded as the SPAD reading for each plant. The above-ground parts of the plants were harvested, labeled, and weighed to determine fresh biomass. Samples were then placed in an oven at 105°C for 30 minutes to halt enzymatic activity, followed by drying at 70°C to constant weight for dry biomass determination. Total phosphorus (TP) content in the shoot was analyzed using the molybdenum-antimony colorimetric method, while total potassium (TK) was measured using a flame photometer. The root part : roots were carefully washed, dried with absorbent paper, and placed into pre-labeled envelopes. Fresh root biomass was recorded before oven treatment at 105°C for 30 minutes, followed by drying at 70°C until constant weight. Root total phosphorus (TP) and total potassium (TK) contents were determined using the same methods as for the shoot samples: the molybdenum-antimony colorimetric method for TP and flame photometry for TK. The soil part : Soil organic matter was measured using the potassium dichromate oxidation method with external heating. Available phosphorus (AP) was determined using the molybdenum-antimony colorimetric method, and available potassium (AK) was measured using a flame photometer. Total nitrogen (TN) content was determined using the Kjeldahl method. Soil pH was measured potentiometrically at a soil-to-water ratio of 1:2.5.Soil microbial populations (bacteria, fungi, and actinomycetes) were assessed through serial dilution and plate culture techniques. Selective media were used for microbial enumeration: peptone medium for bacteria, Martin’s medium for fungi, and Gao's medium for actinomycetes. 2.4 Data analysis and processing Data were processed and statistically analyzed using Microsoft Excel 2021 and IBM SPSS Statistics 26. A one-way analysis of variance (ANOVA) followed by Least Significant Difference (LSD) tests was used to evaluate differences between control and treatment groups. A two-way ANOVA was conducted to assess the main effects and interaction effects between different organic matter types and microbial inoculant dosages on wheat growth and soil properties. Origin 2024 software was employed to calculate the mean and standard error (SE), generate comparison differences among multiple groups, and perform correlation analysis. Redundancy analysis was performed by Canoco5 software to identify the key factors affecting wheat growth. Structural equation modeling was conducted to explore the complex relationship among variables using R Software. To comprehensively evaluate treatment effects, principal component weighting analysis was used to calculate the membership function value (MFV) of each treatment, following methods used in previous studies. The relative weight (Wi) of each indicator was determined based on principal component analysis, using the factor loadings (L) and contributions (C) of each extracted component: (Ⅰ) \(\:{\:E}_{x}={\sum\:}_{y=1}^{n}({L}_{xy}\times\:{C}_{xy})\) (Ⅱ) \(\:{\:W}_{x}={E}_{x}/\sum\:{E}_{x}\) Where: Lxy is the loading of indicator x on the yth principal component; Cxy is the contribution rate of the yth principal component; N is the number of components extracted; Wx is the relative weight of indicator xxx. MFV in fuzzy mathematics is calculated as follows: $$\:{\left(\text{Ⅲ}\right)\:M}_{y}=({X}_{y}-{X}_{min})/({X}_{max}-{X}_{min})$$ Where: My is the membership function value of indicator y; Xy is the measured value of indicator y; Xmin and Xmax are the minimum and maximum values of the measured value of y indicator. Finally, the MFV of the comprehensive evaluation is obtained: (Ⅳ) \(\:\:MFV={W}_{x}\times\:{M}_{x}\) 3 Results 3.1 Interactive effects of organic materials and microbial inoculants on wheat growth traits Wheat growth traits including, plant height, stem diameter, leaf surface, and SPAD responded significantly to the application of organic matter. Among these, only leaf area showed a significant response to the microbial inoculant gradients. All traits, except plant height, were significantly influenced by the interaction between organic materials and microbial inoculant levels (Table 2 ). Plant height generally decreased under most treatments compared to the control (CK), except under BC1 and BC2, which showed an increase (Fig. 1 a). Leaf area significantly improved in the BC group, particularly under BC3, BC4, and BC5 treatments, with BC4 exhibiting the highest increase (42.17%) relative to CK (Fig. 1 b). SPAD values declined in most treatments, except for BC5, which recorded a slight increase compared to CK (Fig. 1 c). Stem diameter was consistently greater under BC treatments, with the highest increase observed in BC1, reaching 49.77% above CK levels CK (Fig. 1 d). Table 2 Results of two-factor ANOVA of organic material and microbial inoculants Traits Organic material ( DF = 2) Microbial inoculant gradients (DF = 4) Organic material × microbial inoculant gradients (DF = 8) PH (cm) 18.753*** 1.022 1.544 SD (mm) 107.228*** 0.99 8.087*** LS (cm²) 38.969*** 3.631* 6.383*** SPAD (mg/g) 45.898*** 0.502 2.492* SFW (g) 170.760*** 3.230* 11.210*** SDW (g) 63.087*** 32.369*** 42.129*** RFW (g) 46.232*** 9.723*** 9.638*** RDW (g) 63.911*** 14.398*** 17.834*** pH 1.007 1.484 0.883 OM (g/kg) 13.137*** 1.803 1.288 TN (g/kg) 42.289*** 6.395*** 18.457*** AP (mg/kg) 19.549*** 7.265*** 5.491*** AK (mg/kg) 198.912*** 0.876 3.634** SN (%) 141.602*** 8.463*** 2.384* SP (%) 257.563*** 16.844*** 19.240*** SK (%) 130.399*** 1.845 2.795* RN (%) 30.429*** 5.509*** 10.662*** RP (%) 94.298*** 6.218*** 14.351*** RK (%) 27.204*** 12.827*** 12.419*** BAC (×10 7 CFU/g) 202.160*** 51.450*** 140.642*** FUN (×10 4 CFU/g) 3512.256*** 59.027*** 65.730*** ACT (×10 7 CFU/g) 316.262*** 155.391*** 241.270*** Note: ∗, ∗∗ and ∗∗∗ were significant at P < 0.05, P < 0.01 and P < 0.001, respectively. Two-factor analysis of variance excluded CK processed data. Abbreviations: PH—plant height; SD—stem diameter; LS—leaf surface area; SPAD—chlorophyll; SFW—shoot fresh weight; SDW—shoot dry weight; RFW—root fresh weight; RDW—root dry weight; pH—soil pH; OM—organic matter; TN—total nitrogen; AP—available phosphors; AK—available potassium; SN—shoot total nitrogen content; SP—shoot total phosphorus content; SK—shoot total potassium content; RN—root total nitrogen content; RP—root total phosphorus content; RK—root total potassium content; BAC—bacteria; FUN—fungi; ACT—actinomyces. 3.2 Interactive effect of organic materials and microbial inoculants on wheat biomass Among all the biomass traits; shoot fresh/dry weight, and root fresh/dry weight responded significantly to the organic matters and microbial inoculant gradients individual and also under combined treatment of these materials (Table 2 ). The shoot fresh weight and dry weight was increased by 99.68% and 69.19%, respectively, under BC treatment (Fig. 2 a), which was highest value under BC1 treatment. This indicated that combined organic matters and microbial inoculants in BC had a significant impact on the shoot growth. The most intrigue results were obtained under MS5 treatment, which showed an increase of 505.60% and 568.32% in the root fresh weight and shoot dry weight, respectively (Fig. 2 b). All these results recommended that organic matters and microbial inoculants synergistically promotes the wheat growth. 3.3 Combined effect of organic materials and microbial inoculants on the soil physiochemical properties Among the soil physicochemical properties, all parameters except pH; soil organic matter, total nitrogen (TN), available phosphorus (AP), and available potassium (AK) showed significant responses to organic materials (Table 2 ). TN and AP also responded significantly to the microbial inoculant gradients, and TN, AP, and AK were significantly affected by the interaction between organic inputs and microbial inoculant levels. Soil pH showed no significant differences across treatments (Fig. 3 a). Organic matter content increased under all combined treatments, with the highest increase observed in BC4 (117.12% over CK) (Fig. 3 b). TN content increased in all treatments except WS3 and WS4, with BC3 showing the highest increase (65.48%) compared to CK (Fig. 3 c). AP content was highest in the BC treatments, peaking under BC3 with a 34.17% increase over CK (Fig. 3 d). AK content significantly increased across all treatments, with the greatest enhancement in BC5, showing a 121.50% increase compared to CK (Fig. 3 e). 3.4 Effect of organic inputs and microbial inoculants on nutrient accumulation in wheat All measured nutrient indicators including shoot and root nitrogen (N), phosphorus (P), and potassium (K) contents exception of shoot K content positively enhanced with the addition of organic materials and microbial inoculants individually, as well as combined (Table 2 ). Wheat under BC treatments showed the highest nutrient accumulation for N. Shoot N content were highest with an increase of 61.51% under BC3 compared to CK, while root N content was 29.47% greater in BC2 (Fig. 4 a). Shoot P content was 87.86% higher compared to CK under WS3. Root P content was 68.60% higher under BC5 (Fig. 4 b). Shoot K content showed no obvious differences among all these treatments; however, root K content increased 101.89% compared to CK substantially under BC5 (Fig. 4 c). 3.5 The effect of organic materials and microbial inoculants on soil microbial population Soil microbial populations which include bacteria, fungi, and actinomycetes showed significant alterations in response to the addition of organic materials, microbial inoculants, and their interaction (Table 2 ). BC treatments notably promoted bacterial abundance, with the population increasing consistently across inoculant gradients. The highest bacterial count was 266.27% compared to CK under BC5, (Fig. 5 a). The fungal populations were enhanced 610.20% compared to CK under WS treatments, with a maximum increase observed under WS5 (Fig. 5 b). The MS5 treatment showed 361.64% growth of actinomycetes compared to CK (Fig. 5 c), which supports the strategy to apply maize straws along with microbial inoculants results into the higher actinomycete proliferation. 3.6 Correlation and redundancy analysis of wheat traits under organic materials and microbial inoculant treatments Redundancy analysis indicated that physiochemical properties and microbial population of the soil and the growth indicators of wheat showed a total 50.12% variation, with a contribution of 35.62% for axis I and 14.50% for axis II (Fig. 6 ). Correlation analysis showed significant associations between various growth and development indicators of wheat and soil nutrient status and microbial populations (Fig. S1 , Fig. 6 ). Results indicated that plant height, stem diameter, and leaf surface area all had highly significant positive correlations with shoot N and K content. Conversely, plant height and stem diameter were negatively correlated with shoot P content, indicating direct relationship between wheat growth parameters and nutritional status. A direct relationship between physiochemical properties of soil and wheat plant nutrient was found with the enhanced shoot N and K level in response to organic matter. Moreover, a positive correlations of bacteria, with the SPAD, leaf surface area, AP content, AK content, shoot N content, root P content, and root K content was observed. Additionally, a highly significant positive correlation of actinomycetes with shoot dry weight, root fresh weight and dry weight was also determined. However, negative correlations were observed among fungi and stem diameter, SPAD, shoot fresh weight, shoot N, and K content which indicated the close relationship of microbial populations with the soil physiochemical properties, plant biomass, and nutrient parameters (Fig. S1 , Fig. 6 ). 3.7 Comprehensive analysis of organic materials and microbial inoculants application Affiliation functional analysis revealed that biochar was the most effective treatment followed by the maize, and then wheat straw which was found to be the least effective treatment (Fig. 7 a). Among all the treatments, the top five composite scores of wheat indicators under different treatments were ranked as BC3 > BC5 > MS5 > BC4 > BC2 (Fig. 7 a), indicating the highest score of 0.73 which was 193.87% higher compared to CK, under BC3 treatment,. Similarly, the soil traits were also analyzed under the organic materials and microbial inoculant agents. The effectiveness pattern was as ; BC3 > BC2 > BC4 > WS5 > BC5 (Fig. 7 b). The highest score was 0.67 which was 331.25% compared to CK under the BC treatment, (Fig. 7 b). 3.8 Structural equation modeling analysis Among all explanatory variables, soil fungi had the greatest influence on wheat growth, contributing 41.7% to the model with a highly significant effect (P < 0.002), followed by available potassium (AK, 21.8%), actinomycetes (18.7%), bacteria (6.8%), and available phosphorus (AP, 4.7%) (Table 3 ). Fungi, AK, actinomycetes, bacteria and soil AP content were selected as the main environmental factors to analyze the effects of soil microbial populations and soil physiochemical properties on the growth of wheat through structural equation modeling. The different carbon sources negatively influence the fungi population in the soil which showed a positive effect on plant height, stem diameter, leaf surface area and SPAD of wheat (Fig. 8 a, 8 b, 8 c, 8 d). Secondly, plant height, stem diameter and leaf surface area of wheat was also enhanced with the modulation of AP and AK content in the soil (Fig. 8 a, 8 b, 8 c). Different carbon sources were positively correlated with shoot and root fresh weight of wheat (Fig. S2a, S2b). Different concentrations of microbial inoculant directly affected leaf surface area and root dry weight (Fig. 8 c, 8 f). It was also found that different carbon sources also affected shoot N, P, K and root P, K content by affecting the fungal population in the soil (Fig. 9 a, 9 b, 9 c, 9 e, 9 f). Additionally, carbon sources also had a direct effect on root N, P content and root K content (Fig. 9 d, 9 e, 9 f). It was noteworthy that different concentrations of microbial inoculant also had a direct effect on shoot N, P, K and root Kcontent in wheat (Fig. 9 a, 9 b, 9 c, 9 f). Table 3 Redundancy analysis of explanatory variables for differences in wheat growth indicators Explanatory variable Contribution rate (%) F value P value FUN 41.7 20.7 0.002 AK 21.8 12.9 0.002 ACT 18.7 13.3 0.002 BAC 6.8 5.2 0.002 AP 4.7 3.7 0.004 TN 2.9 2.4 0.018 pH 1.9 1.6 0.11 OM 1.5 1.2 0.288 Abbreviations: pH—soil pH; OM—organic matter; TN—total nitrogen; AP—available phosphors; AK—available potassium; BAC—Bacteria; FUN—fungi; ACT—actinomyces. 4 Discussion 4.1 Effects of organic materials and microbial inoculants on crop growth indicators Crop growth parameters are considered as the criteria to assess the crop development and productivity[ 14 ]. In this study, we optimized four growth indicators under BC treatment, and variable concentrations of different microbial inoculant and found (Fig. 1 ). Among all parameters of plant growth, plant height can be observed obviously and prominently and is closely related to crop yield[ 15 , 16 ]. This study showed that plant height was enhanced by 8.23% and 8.44% after BC input compared to WS and MS, respectively (Fig. 1 a). Compared to straw, biochar has a porous structure and is rich in organic carbon, nitrogen, phosphorus, potassium and other beneficial nutrients which promotes plant height and leaf differentiation[ 17 ]. We found 0.81%-42.17% increase in leaf surface area as compared to CK, with the addition of biochar along with different concentrations of microbial inoculant (Fig. 1 b). As a key indicator of photosynthesis, SPAD can directly affect the growth rate and yield of crops[ 19 ]. However, this study showed that chlorophyll was lower under different organic materials along with microbial inoculants compared to CK (Fig. 1 c). Stem diameter reflects the structural strength and support capacity of the crop, and directly linked with the efficiency of nutrient uptake and transportation[ 20 ]. Biochar with different concentrations of microbial inoculant were effectively promoted the stem diameter by 13.74%-49.77% than CK (Fig. 1 d). Biochar improves soil structure, water retention and aeration, which helps to improve stalk thickness and length[ 21 ]. 4.2 Effects of organic materials and microbial inoculants on biomass and nutrient accumulation Shoot fresh and dry weights are collectively considered as crop biomass and also key indicators for assessing crop growth and yield[ 22 ]. Shoot fresh and dry weights were enhanced under the BC treatment (Fig. 2 a). This can be attributed to the optimization of the soil condition through the proper formulation of microbial inoculant, which promotes plant growth and consequently increases plant biomass[ 23 ]. Previous researchers have also reached the same conclusion through their studies on rice[ 24 ]. In this study, the results showed that both indicators were optimized with the three organic materials and microbial inoculants, but there were significant differences between treatments and microbial inoculant concentrations (Fig. 2 b). Various crops have different responsive mechanisms with the addition and concentrations of fertilizers[ 25 ]. The total amount of nitrogen, phosphorus and potassium elements accumulated in the shoot of the plant, which are essential for plant growth, development and morphology[ 26 ]. Similarly, in this study, shoot N, P, and K levels varied significantly with the addition of different concentrations of microbial inoculant. In this study, the shoot P content was the lowest and shoot N content was the highest under BC treatment, while the opposite results were observed in WC treatment (Fig. 3 ). Biochar promotes soil microbial activity and increases the rate of nitrogen mineralization, thus increase the supply of effective nitrogen in the soil[ 8 ]. Under WS treatment, the higher microbial population requires to decompose the straw and nitrogen availability, while the decomposition of organic acids promotes the efficacy of soil phosphorus, resulting in the lowest N content and the highest P content in shoot[ 27 ]. Shoot N, P and K content in the subsurface also showed significant differences among the treatments, but most of the growth parameters were significantly promoted under the BC treatment (Fig. 3 ). Research showed that microorganisms in the microbial inoculants can promote the transformation and cycling of nutrients in the soil, and increase the biomass and nutrient level in the subsoil[ 28 ]. 4.3 Effect of treatments on soil physicochemical properties Previous studies have shown that soil physiochemical properties improve soil and crop root health, which ultimately promotes crop yield and quality[ 29 ]. Soil properties were optimized with the addition of BC treatment (Fig. 3 ). Organic materials consists of different organic acids and minerals that helps to cope up the effects of environmental changes and also stabilize the soil pH, that’s why pH in the soil treated with organic materials and microbial inoculants did not differ much compared to the CK treatment (Fig. 4 a)[ 30 ]. Previous study has indicated that there are significant differences between the different organic materials and microbial inoculant gradients. The overall trend of growth parameters and microbial inoculant gradients is first increased and then declined[ 31 ]. This indicates that all treatments were significantly better than the CK treatment (Fig. 4 b). Therefore, the level of total nitrogen content is directly linked with the nitrogen supply capacity of the soil and crop growth conditions[ 32 ]. The optimized concentrations of microbial inoculant have a significant effect on soil nitrogen content and crop growth[ 33 ]. The TN content in this study was significantly increased with the addition of MS and BC compared to CK (Fig. 4 c). Previous studies have found that microbial inoculants can significantly alter the composition of soil microbial communities that helps to enhance the nitrogen fixation ability of soil, similarly with this study[ 34 ]. The TN content was significantly increased with the application of MS and BC compared to the CK (Fig. 4 c). AP content varied considerably under different treatments (Fig. 4 d), which may be related to the effects of soil physiochemical properties and differences in crop requirements. AK content can improve the disease resistance of crops and promote the crop growth[ 35 ]. Previous studies also showed that the highly aromatic structure and rich pore space of biochar provided ideal adhere and habitat sites for microorganisms, whereas, wheat and maize straw, despite the source of organic matter, had different effects on microbial activity and nutrient availability[ 36 ]. All these facts answers that why the AK content showed a negative correlation respective to the different levels of BC treatment, but a positive correlation in WS and MS treatments (Fig. 4 e). 4.4 Response of soil microbial populations to organic inputs and microbial inoculant dsosages Previous studies have shown that, soil microbial population is usually referred to the huge microbial communities such as bacteria, fungi, actinomycetes, in soil, which play a pivotal role in the decomposition of organic matter, recycling of nutrients, conversion of energy, and suppression of diseases soil[ 37 ]. There are significant differences in the performance of soil microbial populations under different treatment conditions. The results of this study showed that three microorganisms (bacteria, fungi, and actinomycetes) differed significantly among the different microbial inoculant doses as compared to CK. For instance, bacteria being the most abundant in the BC treatment, fungi in the WS treatment, and actinomycetes in the MS treatment (Fig. 5 ).The findings in this study are consistent with previous studies[ 38 , 39 ]. In addition, the study also showed that the dosing of different concentrations of microbial inoculant also significantly affected the changes in the microbial community[ 40 ]. The optimal efficacy of all these micoorganisms can be attained, when 100% concentration of microbial inoculant will be applied in the soil. However, research has demonstrated that elevated or diminished concentrations of microbial inoculant can exert negative effects on the microbial community[ 41 ]. Therefore, the appropriate concentrations of microbial inoculant are mandatory according to the specific soil type, crop requirements and developmental stages [ 42 ]. 4.5 Influence of microbial communities and carbon sources inputs on wheat growth and nutrient uptake Elevated fungal populations in the soil inhibit plant height and chlorophyll content in wheat by reducing nutrient availability[ 43 ]. This study indicated that, alteration in fungal population were negatively correlated with wheat growth indicators (Fig. 8 a, 8 b, 8 c, 8 d). The different carbon sources indirectly affected plant height, leaf surface area and stem diameter of wheat by modifying the AP content in the soil (Fig. 8 a, 8 b, 8 c). The application of different carbon sources might help to promote the phosphorus mineralization, which enhance phosphorus absorbance capability in by wheat, thus promoting growth and development[ 44 ]. Different carbon sources decrease the shoot fresh and dry weight by affecting bacterial and fungal populations (Fig. 8 e and S2). The underlying cause may be attributed to the competition between bacteria and roots for nutrients, as well as the impact of fungi on the conversion of organic matter and the availability of water nutrients[ 45 ]. Different carbon sources significantly affected the K content in shoot, whereas, and P and K level in root indirectly by regulating soil AK content. Conversely, N and P content in shoot and also N content in root was positively affected by regulating soil AP content (Fig. 9 ). Carbon sources not only directly influence the structure of microbial communities, but may also indirectly affect plant nutrient uptake by influencing soil nutrient cycling[ 46 ]. In addition to root N content, microbial inoculants had a significant effect on the shoot N, P content, and K content, as well as root P and K content in wheat plants with the altered fungal population in soil (Fig. 9 ). Microbial inoculants alter the soil microbial environment and nutrient cycling, which in turn affects nutrient utilization of wheat [ 47 , 48 ]. 5 Conclusions The optimized concentrations of microbial inoculant significantly increase the growth indicators and biomass of wheat, the nutrient level of the plant, moreover, improve physiochemical properties of soil, as well as the number and diversity of microorganisms in the soil compared with traditional fertilization treatments. Significant differences were found among the treatment groups with different carbon sources. Biochar with microbial inoculants was more effective as compared to the wheat and maize straw inoculated with the same microbial inoculants. The best recommended fertilization for enhanced shoot and root growth is the conventional fertilization along with the addition of biochar and optimized amount of Bacillus subtilis. Therefore, the application of different types of organic materials, especially the combined use of biochar and microbial inoculants, should be actively promoted in wheat production. This combined application will not only help to improve the yield and quality of crops, but also the soil ecosystem which promote the development of sustainable agriculture. Declarations Authorship contribution statement Miao Wang: experiments, investigations, methods, software, visualization, writing-preliminary drafts, writing-commentary and editing. Chi Zhang: experimentation, investigation, methods, software, visualization, writing-preliminary draft, writing-commenting and editing. Hong Wang: research, writing-commenting and editing. Li Wang: experiments, investigations, methods. Rufang Zhang: conceptualization, funding acquisition, project management, research, writing-commenting and editing. Xuguang Li: situation analysis, research, writing-criticism and editing. Xin-Xin Wang: experimentation, methodology, software, research, writing-criticism and editing. Consent for publication Not applicable. Availability of Data and Materials The original data supporting the conclusions of this paper will be provided by the author without reservation, and data is provided within the supplementary information files. Ethics approval and consent to participate There was no requirement to seek ethical approval to carry out the work described above. Declaration of competing interest The authors declare that they have no competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7018728","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":485367884,"identity":"896bbd70-5ba3-4958-8e53-21aa67775ac2","order_by":0,"name":"Miao Wang","email":"","orcid":"","institution":"Hebei Agricultural University","correspondingAuthor":false,"prefix":"","firstName":"Miao","middleName":"","lastName":"Wang","suffix":""},{"id":485367885,"identity":"1aa5f03e-c5b1-49c6-be70-bcd0febddc98","order_by":1,"name":"Chi Zhang","email":"","orcid":"","institution":"Hebei Agricultural University","correspondingAuthor":false,"prefix":"","firstName":"Chi","middleName":"","lastName":"Zhang","suffix":""},{"id":485367886,"identity":"fe77c781-ec9b-44ac-a450-a63be117f72e","order_by":2,"name":"Hong Wang","email":"","orcid":"","institution":"Hebei Agricultural University","correspondingAuthor":false,"prefix":"","firstName":"Hong","middleName":"","lastName":"Wang","suffix":""},{"id":485367888,"identity":"18d6daaa-7c69-4c1e-87d3-c68f1e808491","order_by":3,"name":"Li Wang","email":"","orcid":"","institution":"Hebei Agricultural University","correspondingAuthor":false,"prefix":"","firstName":"Li","middleName":"","lastName":"Wang","suffix":""},{"id":485367889,"identity":"f7c3b618-30bd-4838-aeaa-417ce5e0217a","order_by":4,"name":"Xuguang Li","email":"","orcid":"","institution":"Hebei Cultivated Land Monitoring and Protection Center","correspondingAuthor":false,"prefix":"","firstName":"Xuguang","middleName":"","lastName":"Li","suffix":""},{"id":485367890,"identity":"f5c041a2-02ae-4a1f-b98c-48671a29d0ec","order_by":5,"name":"Ruifang Zhang","email":"","orcid":"","institution":"Hebei Agricultural University","correspondingAuthor":false,"prefix":"","firstName":"Ruifang","middleName":"","lastName":"Zhang","suffix":""},{"id":485367891,"identity":"de631faa-1a6f-4fd9-8c93-e1bd30bf417e","order_by":6,"name":"Xin-Xin Wang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA2UlEQVRIiWNgGAWjYDACZiBOQHBtSNeSRrqlhwkrMTjOe0zi4Y7D8ub8C9ikefecl+07wPzw0Q08WiSb+ZINEs8cNtw54wGbNM+z28YzD7AZG+fg0cLPzGP4ILHtNuOGGwfYbvMcuJ244QAPmzQ+LWzMPAYHgFrsoVrOEdYCsyVxw/kGkJYDhLVINvMYGyS2/U/ecIOx/eecA8nGMw8T8IvB+TNmkj/b0mw3nD982ODNATvZvuPNDx/j04IAEokNIIqxgYiogfnqAANEywGitYyCUTAKRsEIAQAErVHpE1eaRQAAAABJRU5ErkJggg==","orcid":"","institution":"Hebei Agricultural University","correspondingAuthor":true,"prefix":"","firstName":"Xin-Xin","middleName":"","lastName":"Wang","suffix":""}],"badges":[],"createdAt":"2025-07-01 09:38:26","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7018728/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7018728/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":86804424,"identity":"3f5379dd-c2ae-42d1-862e-fdab77a3ac6a","added_by":"auto","created_at":"2025-07-15 17:46:26","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":60030,"visible":true,"origin":"","legend":"\u003cp\u003eEffects of combined application of organic materials and microbial inoculants on wheat growth traits. (a) plant height; (b) leaf surface area; (c) SPAD; (d) stem diameter. Different lowercase letters indicate significant difference between different concentrations of organic materials in the same test (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05); Red starts indicate a significant difference between current processing and conventional processing (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05); Different capital letters indicate significant differences between different organic materials tested (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05), and unlabeled ones indicate no significant differences in results.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7018728/v1/f2c505c2457a8d2cd7939261.png"},{"id":86804425,"identity":"fd9319ff-a578-4221-8942-9a7d2e00ce67","added_by":"auto","created_at":"2025-07-15 17:46:26","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":52010,"visible":true,"origin":"","legend":"\u003cp\u003eEffects of combined application of organic materials and microbial inoculants on wheat biomass. (a) shoot dry/flesh weight; (b) root dry/flesh weight. Different lowercase letters indicate significant difference between different concentrations of organic materials in the same test (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05); Red starts indicate a significant difference between current processing and conventional processing (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05); Different capital letters indicate significant differences between different organic materials tested (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05), and unlabeled ones indicate no significant differences in results.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7018728/v1/a50a86748f96f1d12fc5f78c.png"},{"id":86804426,"identity":"7427925d-969b-47c3-89f9-655deaeeb4bd","added_by":"auto","created_at":"2025-07-15 17:46:26","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":58350,"visible":true,"origin":"","legend":"\u003cp\u003eEffects of combined application of organic materials and microbial inoculants on the nutritional status of wheat. (a) shoot total nitrogen content/root total nitrogen content; (b) shoot total phosphorus content/root total phosphorus content; (c) shoot total potassium content/root potassium content. Different lowercase letters indicate significant difference between different concentrations of organic materials in the same test (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05); Red starts indicate a significant difference between current processing and conventional processing (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05); Different capital letters indicate significant differences between different organic materials tested (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05), and unlabeled ones indicate no significant differences in results.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7018728/v1/96ce79d32ad4a1424590e65c.png"},{"id":86805172,"identity":"8696bbd4-d4b3-4511-b3e9-a1eb73232239","added_by":"auto","created_at":"2025-07-15 17:54:26","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":47953,"visible":true,"origin":"","legend":"\u003cp\u003eEffects of combined application of organic materials and microbial inoculants on soil properties. (a) pH; (b) organic matter; (c) total nitrogen; (d) available phosphorus; (e) available potassium. Different lowercase letters indicate significant difference between different concentrations of organic materials in the same test (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05); Red starts indicate a significant difference between current processing and conventional processing (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05); Different capital letters indicate significant differences between different organic materials tested (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05), and unlabeled ones indicate no significant differences in results.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7018728/v1/7a1277d421c8ac8d96955e08.png"},{"id":86805174,"identity":"d6ccd6d1-d133-48ea-bff8-fb5f416ab34d","added_by":"auto","created_at":"2025-07-15 17:54:26","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":39852,"visible":true,"origin":"","legend":"\u003cp\u003eEffects of combined application of organic materials and microbial inoculants on soil microbial quantity. (a) bacteria; (b) fungi; (c) actinomyces. Different lowercase letters indicate significant difference between different concentrations of organic materials in the same test (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05); Red starts indicate a significant difference between current processing and conventional processing (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05); Different capital letters indicate significant differences between different organic materials tested (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05), and unlabeled ones indicate no significant differences in results.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-7018728/v1/487eea59c686ad9c8d1cef8c.png"},{"id":86804434,"identity":"bbea0b87-97bd-4ae2-a81c-112e33618292","added_by":"auto","created_at":"2025-07-15 17:46:27","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":85039,"visible":true,"origin":"","legend":"\u003cp\u003eVisualization of redundancy analysis of wheat growth indicators and soil characteristics. Abbreviations: pH—soil pH; OM—organic matter; TN—total nitrogen; AP—available phosphors; AK—available potassium; BAC—bacteria; FUN—fungi; ACT—actinomyces.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-7018728/v1/ffe26324bf189a00b97ad79d.png"},{"id":86804441,"identity":"f5f5846d-b128-4aea-b7a8-12dcc1cca6f5","added_by":"auto","created_at":"2025-07-15 17:46:27","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":80752,"visible":true,"origin":"","legend":"\u003cp\u003eCombined scores of wheat growth and soil parameters under organic matter and microbial inoculants formulation. (a) comprehensive affiliation function values of wheat growth traits; (b) comprehensive affiliation function values of soil indicators. Different lowercase letters indicate significant differences between different treatment treatments (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05).\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-7018728/v1/0674961b40064c867319d65e.png"},{"id":86805173,"identity":"d8c2752b-d648-4b6d-9b42-6e0e998b0deb","added_by":"auto","created_at":"2025-07-15 17:54:26","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":534720,"visible":true,"origin":"","legend":"\u003cp\u003eCombined scores of wheat growth and soil parameters under organic matter and microbial inoculants formulation. (a) comprehensive affiliation function values of wheat growth traits; (b) comprehensive affiliation function values of soil indicators. Different lowercase letters indicate significant differences between different treatment treatments (\u003cem\u003eP\u003c/em\u003e\u0026lt;0.05).\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-7018728/v1/e80ff43a93ed43f457db35fe.png"},{"id":86805175,"identity":"48c265ee-1ccc-4839-99de-8304d2e5884e","added_by":"auto","created_at":"2025-07-15 17:54:26","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":514799,"visible":true,"origin":"","legend":"\u003cp\u003eStructural equation modeling (SEM) of wheat growth traits and shoot and root dry weights. (a) plant height; (b) stem diameter; (c) leaf surface area; (d) Chlorophyll; (e) shoot dry weight; (f) root dry weight. Abbreviations: PH—plant height; SD—stem diameter; LS—leaf surface area; SPAD—chlorophyll; SDW—shoot dry weight; RDW—root dry weight; BAC—bacteria; FUN—fungi; ACT—actinomyces; AP—Available phosphors; AK—Available potassium. χ\u003csup\u003e2\u003c/sup\u003e: chi-square value, DF: degree of freedom, GFI: fitness index, RMSEA: root mean square of the error of approximation; * denotes \u003cem\u003eP\u003c/em\u003e\u0026lt;0.05, ** denotes \u003cem\u003eP\u003c/em\u003e\u0026lt;0.01, and *** denotes \u003cem\u003eP\u003c/em\u003e\u0026lt;0.001; red arrows denote a significant positive effect, blue arrows denote a significant negative effect, the thickness of the arrow line denotes the magnitude of the path coefficients in the model, and the yellow dashed line denotes no significant effect.\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-7018728/v1/93cefc1e8ff47cfcbace5d3f.png"},{"id":86806050,"identity":"924cabea-a0cc-4aec-93fe-cf00f1a23970","added_by":"auto","created_at":"2025-07-15 18:10:28","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2666839,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7018728/v1/4a370ac6-c312-4564-97e7-37923025e3be.pdf"},{"id":86804432,"identity":"b2831c6f-8fb1-403d-b2cb-fd0c02bb6504","added_by":"auto","created_at":"2025-07-15 17:46:26","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":331024,"visible":true,"origin":"","legend":"","description":"","filename":"Supportingmaterials.docx","url":"https://assets-eu.researchsquare.com/files/rs-7018728/v1/3ae4939b13bd5b526685d088.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Integrated effects of organic amendments and microbial inoculants on soil quality and wheat growth performance","fulltext":[{"header":"1 Introduction","content":"\u003cp\u003eThe increasing global population and ongoing economic development have led to a steady rise in food demand. As a foundation of agricultural production, soil quality is critical for maintaining stable and enhanced crop yields. Improved soil conditions enhance crop resistance to pests and diseases, thereby minimizing the need for chemical fertilizers and pesticides and promoting sustainable agricultural development[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Healthy soil enhances root growth and nutrient uptake, supporting high crop yields under different climatic and environmental conditions, and contributing to national food security. Fertilizers play a vital role by supplying essential nutrients to boost yields. However, excessive long-term use of chemical fertilizers has led to soil degradation and environmental pollution, complicating their role in sustainable food production[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. The long-term over-application of chemical fertilizers alter soil physiochemical properties, particularly pH, nutrient balance and organic matter content. This imbalance can cause micronutrient excesses or deficiencies and suppress soil microbial diversity and activity, ultimately reducing soil fertility. Over-reliance on chemical fertilizers further exacerbates soil degradation and but nutrient imbalances in the soil that affect crop growth and quality[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe drive for increased food production, coupled with excessive fertilization and irrational farming practices, has significantly degraded soil quality amid ongoing agricultural modernization[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. These issues have diminished the soil fertility and accelerated degradation, becoming major constraints to food production and sustainable agricultural development. Declining arable land quality limits crop growth, reducing yield and quality, and significantly hinders the sustainable development of regional agriculture, especially in areas with intensive production[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Degradation of arable land quality not only hinders the improvement of agricultural productivity, but also threatens the stability of agro-ecosystems, intensifying challenges to sustainable agriculture. Addressing this requires a shift toward more scientific and sustainable management practices. Promoting green agriculture, enhancing soil remediation, adopting eco-agricultural technologies, and reducing dependence on chemical inputs are essential for restoring soil ecological functions and ensuring long-term agricultural sustainability[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Therefore, contemporary agricultural research focuses on improving soil quality and fostering the sustainable agriculture while augmenting food production. In this context, researchers are actively exploring alternative fertilization strategies, with growing attention on the combined use of straw return, biochar, and microbial inoculants. \u0026ldquo;Returning straw\u0026rdquo; refers to the process, of returning the remaining to incorporate the straw back into the soil after the crop harvest. This practice not only increase soil fertility and improves soil structure effectively, but also reduce the soil hazards associated with excessive application of chemical fertilizers[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Biochar is a highly aromatic, nitrogen-rich carbonaceous material produced by high-temperature pyrolysis under anoxic or low-oxygen condition[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Biochar can adsorb harmful substances and heavy metals in the soil, improve soil structure and increase soil fertility, maintaining a positive soil environment for crop growth[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Microbial inoculants are live beneficial microorganisms that are produced by industrialized expansion and processing. The microbial inoculants have a significant impact on agricultural production, improving soil health and crop yields, and effectively reducing reliance on chemical fertilizers and pesticides, thereby promoting sustainable agricultural development[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Although individual applications of straw, biochar and microbial inoculants are effective in enhancing the quality of cropland and boosting agricultural production, the research indicates that the combination of these applications is more effective in increasing crop yields and soil improvement than individual applications[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. In addition, the combination of fertilizers can balance the nutrients in the soil, avoiding the problems of over-application and environmental pollution. The optimized combination of different organic matter components, it can improve the efficiency of nutrient absorption by crops, reduce the waste of fertilizers, reduce the risk of pollution of water sources and soil, and consequently augment the yield and quality of crops[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Therefore, the rational use of straw and biochar can improve the physical structure of soil, increase soil organic matter, and improve the water retention capacity and permeability of soil, while microbial inoculants can promote the propagation of soil microorganisms, enhance the biological activity of soil, and the efficiency of nutrient recycling[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eIn this study, we investigated the effect of different organic materials with microbial inoculants on the growth and development of wheat in greenhouse. This study aims to identify the best combination of organic materials and microbial inoculants, analyze their effects on the growth, yield and quality of wheat, and explore the optimization of soil fertility, nutrient cycling and microbial community structure.\u003c/p\u003e"},{"header":"2 Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1 Experimental materials\u003c/h2\u003e\u003cp\u003eThe experimental soil was collected from the field of Beishao Village, Dingzhou City, Hebei Province, China (38\u0026deg;23\u0026prime;44.39\u0026Prime;N, 115\u0026deg;5\u0026prime;8.76\u0026Prime;E). The soil has a pH of 7.72, which is close to neutral and suitable for most plants, with positive nutrient availability. The experiment was conducted in a light-controlled chamber of the west campus of Hebei Agricultural University (115.45\u0026deg;E, 38.82\u0026deg;N). The wheat plants (Gaoyou No. 1) were sown in the plastic flowerpot (16 cm in diameter and 17 cm in height). The test tissues were wheat straw (WS), maize straw (MS), biochar (BC), and Bacillus subtilis bacterial agent (screened for silage fermentation feed, with a bacterial content of 1.0\u0026times;10\u003csup\u003e10\u003c/sup\u003e CFU/g). The conventional fertilizer applied was Huaxin compound fertilizer (N-P\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e5\u003c/sub\u003e-K\u003csub\u003e2\u003c/sub\u003eO, 24-6-10), purchased from Shanxi Huaxin Fertilizer Co. The basic physicochemical properties were as: organic matter content of 9.96 g/kg, which contributes to the maintenance of soil fertility and microbial activity. The total nitrogen content of 0.89 g/kg is moderately low and may require supplemental nitrogen fertilizer for proper crop growth. The available phosphorus content was 11.06 mg/kg, which was more adequate and could support the phosphorus nutritional requirements of plants. The available potassium content was 83.17 mg/kg, which was favorable to the healthy growth and resistance of the crop. Overall, the nutrient profile of this soil is relatively balanced, but the nitrogen content is slightly deficient, requiring proper fertilization according to crop needs.\u003c/p\u003e\u003cp\u003eThe test materials used in this experiment was biochar, wheat straw, and maize straw and their respective properties were as follows: Biochar contained 369.28 g/kg organic carbon, 5.04 g/kg total nitrogen, 1.85 g/kg total phosphorus, 32.19 g/kg total potassium, and had a pH of 7.63. Wheat straw had 389.14 g/kg organic carbon, 4.11 g/kg total nitrogen, 0.70 g/kg total phosphorus, 16.82 g/kg total potassium, and a pH of 6.74. Maize straw contained 404.44 g/kg organic carbon, 9.51 g/kg total nitrogen, 1.28 g/kg total phosphorus, 12.58 g/kg total potassium, and a pH of 7.40.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2 Experimental design\u003c/h2\u003e\u003cp\u003eThe trial was conducted from August 1, 2023 to September 27, 2023. The experiment was a completely randomized experimental design with three material treatments (wheat straw, maize straw, and biochar) and five microbial inoculants concentrations (0 ml (0%), 2.50 ml (25%), 5.00 ml (50%), 7.50 ml (75%)), and 10.00 ml (100%) per pot). A control treatment (conventional fertilization without straw or microbial inoculants) was included, resulting in a total of 16 treatments. Each treatment was replicated four times, for a total of 64 pots. Plastic pots (16 cm diameter \u0026times; 17 cm height) were filled with 2 kg of sieved soil. The nutrients were uniformly mixed in soil prior to the potting. The 10 seeds per pot at a depth of 2 cm were sown on August 1\u003csup\u003est\u003c/sup\u003e, 2023. After germination, seedlings were thinned to three per pot. Pots were repositioned weekly to minimize positional bias. Soil moisture was maintained at 70% of field capacity using the weighing method. Throughout the experiment, light intensity was maintained at 9000 Lux with a 14-hour photoperiod (6:00\u0026ndash;20:00), room temperature was kept at 25\u0026ndash;27\u0026deg;C, and relative humidity ranged from 44\u0026ndash;55%. The experimental treatments are summarized in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eExperimental design\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eCrop plant\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eProcessing number\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eTreatments\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eCarbon sources (g/pot)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\" morerows=\"15\" rowspan=\"16\"\u003e\u003cp\u003eWheat\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eCK\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eRoutine fertilization\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e0\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eWS1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eConventional fertilization\u0026thinsp;+\u0026thinsp;wheat straw\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eWheat straw 30\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eWS2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eConventional fertilizer\u0026thinsp;+\u0026thinsp;wheat straw\u0026thinsp;+\u0026thinsp;bacillus subtilis bacteriophage 25% (2.50 ml)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eWheat straw 30\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eWS3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eConventional fertilizer\u0026thinsp;+\u0026thinsp;wheat straw\u0026thinsp;+\u0026thinsp;bacillus subtilis bacteriophage 50% (5.00 ml)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eWheat straw 30\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eWS4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eConventional fertilizer\u0026thinsp;+\u0026thinsp;wheat straw\u0026thinsp;+\u0026thinsp;bacillus subtilis bacteriophage 75% (7.50 ml)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eWheat straw 30\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eWS5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eConventional fertilization\u0026thinsp;+\u0026thinsp;wheat straw\u0026thinsp;+\u0026thinsp;bacillus subtilis bacteriophage 100% (10.00 ml)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eWheat straw 30\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMS1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eConventional fertilization\u0026thinsp;+\u0026thinsp;maize straw\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eMaize straw 28.87\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMS2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eConventional fertilizer\u0026thinsp;+\u0026thinsp;maize straw\u0026thinsp;+\u0026thinsp;bacillus subtilis bacteriophage 25% (2.5 ml)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eMaize straw 28.87\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMS3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eConventional fertilizer\u0026thinsp;+\u0026thinsp;maize straw\u0026thinsp;+\u0026thinsp;bacillus subtilis bacteriophage 50% (5.00 ml)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eMaize straw28.87\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMS4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eConventional fertilizer\u0026thinsp;+\u0026thinsp;maize straw\u0026thinsp;+\u0026thinsp;bacillus subtilis bacteriophage 75% (7.50 ml)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eMaize straw28.87\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eMS5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eConventional fertilization\u0026thinsp;+\u0026thinsp;maize straw\u0026thinsp;+\u0026thinsp;bacillus subtilis bacteriophage 100% (10.00 ml)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eMaize straw 28.87\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eBC1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eConventional fertilization\u0026thinsp;+\u0026thinsp;biochar\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eBiochar 31.61\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eBC2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eConventional fertilization\u0026thinsp;+\u0026thinsp;biochar\u0026thinsp;+\u0026thinsp;bacillus subtilis bacteriophage 25% (2.50 ml)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eBiochar 31.61\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eBC3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eConventional fertilization\u0026thinsp;+\u0026thinsp;biochar\u0026thinsp;+\u0026thinsp;bacillus subtilis bacteriophage 50% (5.00 ml)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eBiochar 31.61\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eBC4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eConventional fertilizer\u0026thinsp;+\u0026thinsp;biochar\u0026thinsp;+\u0026thinsp;bacillus subtilis bacteriophage 75% (7.50 ml)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eBiochar 31.61\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eBC5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eConventional fertilization\u0026thinsp;+\u0026thinsp;biochar\u0026thinsp;+\u0026thinsp;bacillus subtilis bacteriophage 100% (10.00 ml)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003eBiochar 31.61\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003eNote: The determination of fertilizer amount is based on the principle of keeping the total carbon content in the basic index of the tested material consistent.\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3 Assessment indices and methodologies\u003c/h2\u003e\u003cp\u003e\u003cstrong\u003eThe shoot part\u003c/strong\u003e\u003cp\u003ethe plant height was measured with a tape measure from the soil surface to the apex. Stem diameter was determined 1.0 cm above the soil surface using a digital vernier caliper. The leaf surface area was measured by selecting three uniform leaves and the average value was taken as the leaf surface area of the plant. Chlorophyll content was measured from three-points (upper, middle, and lower portion) of fully expanded leaf of three wheat plants using a portable SPAD-502 chlorophyll meter. The average value recorded as the SPAD reading for each plant. The above-ground parts of the plants were harvested, labeled, and weighed to determine fresh biomass. Samples were then placed in an oven at 105\u0026deg;C for 30 minutes to halt enzymatic activity, followed by drying at 70\u0026deg;C to constant weight for dry biomass determination. Total phosphorus (TP) content in the shoot was analyzed using the molybdenum-antimony colorimetric method, while total potassium (TK) was measured using a flame photometer.\u003c/p\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eThe root part\u003c/b\u003e: roots were carefully washed, dried with absorbent paper, and placed into pre-labeled envelopes. Fresh root biomass was recorded before oven treatment at 105\u0026deg;C for 30 minutes, followed by drying at 70\u0026deg;C until constant weight. Root total phosphorus (TP) and total potassium (TK) contents were determined using the same methods as for the shoot samples: the molybdenum-antimony colorimetric method for TP and flame photometry for TK.\u003c/p\u003e\u003cp\u003e\u003cb\u003eThe soil part\u003c/b\u003e: Soil organic matter was measured using the potassium dichromate oxidation method with external heating. Available phosphorus (AP) was determined using the molybdenum-antimony colorimetric method, and available potassium (AK) was measured using a flame photometer. Total nitrogen (TN) content was determined using the Kjeldahl method. Soil pH was measured potentiometrically at a soil-to-water ratio of 1:2.5.Soil microbial populations (bacteria, fungi, and actinomycetes) were assessed through serial dilution and plate culture techniques. Selective media were used for microbial enumeration: peptone medium for bacteria, Martin\u0026rsquo;s medium for fungi, and Gao's medium for actinomycetes.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4 Data analysis and processing\u003c/h2\u003e\u003cp\u003eData were processed and statistically analyzed using Microsoft Excel 2021 and IBM SPSS Statistics 26. A one-way analysis of variance (ANOVA) followed by Least Significant Difference (LSD) tests was used to evaluate differences between control and treatment groups. A two-way ANOVA was conducted to assess the main effects and interaction effects between different organic matter types and microbial inoculant dosages on wheat growth and soil properties.\u003c/p\u003e\u003cp\u003eOrigin 2024 software was employed to calculate the mean and standard error (SE), generate comparison differences among multiple groups, and perform correlation analysis. Redundancy analysis was performed by Canoco5 software to identify the key factors affecting wheat growth. Structural equation modeling was conducted to explore the complex relationship among variables using R Software. To comprehensively evaluate treatment effects, principal component weighting analysis was used to calculate the membership function value (MFV) of each treatment, following methods used in previous studies. The relative weight (Wi) of each indicator was determined based on principal component analysis, using the factor loadings (L) and contributions (C) of each extracted component:\u003c/p\u003e\u003cp\u003e(Ⅰ)\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\:E}_{x}={\\sum\\:}_{y=1}^{n}({L}_{xy}\\times\\:{C}_{xy})\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\u003cp\u003e(Ⅱ)\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{\\:W}_{x}={E}_{x}/\\sum\\:{E}_{x}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\u003cp\u003eWhere:\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eLxy is the loading of indicator x on the yth principal component;\u003c/p\u003e\u003cp\u003eCxy is the contribution rate of the yth principal component;\u003c/p\u003e\u003cp\u003eN is the number of components extracted;\u003c/p\u003e\u003cp\u003eWx is the relative weight of indicator xxx.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eMFV in fuzzy mathematics is calculated as follows:\u003cdiv id=\"Equa\" class=\"Equation\"\u003e\u003cdiv format=\"TEX\" class=\"mathdisplay\" id=\"FileID_Equa\" name=\"EquationSource\"\u003e\n$$\\:{\\left(\\text{Ⅲ}\\right)\\:M}_{y}=({X}_{y}-{X}_{min})/({X}_{max}-{X}_{min})$$\u003c/div\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eWhere:\u003cdiv class=\"BlockQuote\"\u003e\u003cp\u003eMy is the membership function value of indicator y;\u003c/p\u003e\u003cp\u003eXy is the measured value of indicator y;\u003c/p\u003e\u003cp\u003eXmin and Xmax are the minimum and maximum values of the measured value of y indicator.\u003c/p\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003eFinally, the MFV of the comprehensive evaluation is obtained:\u003c/p\u003e\u003cp\u003e(Ⅳ)\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:\\:MFV={W}_{x}\\times\\:{M}_{x}\\)\u003c/span\u003e\u003c/span\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"3 Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e3.1 Interactive effects of organic materials and microbial inoculants on wheat growth traits\u003c/h2\u003e\u003cp\u003eWheat growth traits including, plant height, stem diameter, leaf surface, and SPAD responded significantly to the application of organic matter. Among these, only leaf area showed a significant response to the microbial inoculant gradients. All traits, except plant height, were significantly influenced by the interaction between organic materials and microbial inoculant levels (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Plant height generally decreased under most treatments compared to the control (CK), except under BC1 and BC2, which showed an increase (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea). Leaf area significantly improved in the BC group, particularly under BC3, BC4, and BC5 treatments, with BC4 exhibiting the highest increase (42.17%) relative to CK (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). SPAD values declined in most treatments, except for BC5, which recorded a slight increase compared to CK (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec). Stem diameter was consistently greater under BC treatments, with the highest increase observed in BC1, reaching 49.77% above CK levels CK (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eResults of two-factor ANOVA of organic material and microbial inoculants\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTraits\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eOrganic material ( DF\u0026thinsp;=\u0026thinsp;2)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eMicrobial inoculant gradients (DF\u0026thinsp;=\u0026thinsp;4)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eOrganic material \u0026times; microbial inoculant gradients (DF\u0026thinsp;=\u0026thinsp;8)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePH (cm)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e18.753***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.022\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.544\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSD (mm)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e107.228***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.99\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e8.087***\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eLS (cm\u0026sup2;)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e38.969***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e3.631*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e6.383***\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSPAD (mg/g)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e45.898***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.502\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2.492*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSFW (g)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e170.760***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e3.230*\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e11.210***\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSDW (g)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e63.087***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e32.369***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e42.129***\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRFW (g)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e46.232***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e9.723***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e9.638***\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRDW (g)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e63.911***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e14.398***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e17.834***\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003epH\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.007\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.484\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.883\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOM (g/kg)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e13.137***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.803\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e1.288\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTN (g/kg)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e42.289***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e6.395***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e18.457***\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAP (mg/kg)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e19.549***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e7.265***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e5.491***\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAK (mg/kg)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e198.912***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e0.876\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e3.634**\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSN (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e141.602***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e8.463***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2.384*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSP (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e257.563***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e16.844***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e19.240***\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSK (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e130.399***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.845\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e2.795*\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRN (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e30.429***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e5.509***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e10.662***\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRP (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e94.298***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e6.218***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e14.351***\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRK (%)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e27.204***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e12.827***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e12.419***\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBAC (\u0026times;10\u003csup\u003e7\u003c/sup\u003e CFU/g)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e202.160***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e51.450***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e140.642***\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFUN (\u0026times;10\u003csup\u003e4\u003c/sup\u003e CFU/g)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e3512.256***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e59.027***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e65.730***\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eACT (\u0026times;10\u003csup\u003e7\u003c/sup\u003e CFU/g)\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e316.262***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e155.391***\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e241.270***\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003eNote: \u0026lowast;, \u0026lowast;\u0026lowast; and \u0026lowast;\u0026lowast;\u0026lowast; were significant at \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.05, \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.01 and \u003cem\u003eP\u003c/em\u003e\u0026thinsp;\u0026lt;\u0026thinsp;0.001, respectively. Two-factor analysis of variance excluded CK processed data. Abbreviations: PH\u0026mdash;plant height; SD\u0026mdash;stem diameter; LS\u0026mdash;leaf surface area; SPAD\u0026mdash;chlorophyll; SFW\u0026mdash;shoot fresh weight; SDW\u0026mdash;shoot dry weight; RFW\u0026mdash;root fresh weight; RDW\u0026mdash;root dry weight; pH\u0026mdash;soil pH; OM\u0026mdash;organic matter; TN\u0026mdash;total nitrogen; AP\u0026mdash;available phosphors; AK\u0026mdash;available potassium; SN\u0026mdash;shoot total nitrogen content; SP\u0026mdash;shoot total phosphorus content; SK\u0026mdash;shoot total potassium content; RN\u0026mdash;root total nitrogen content; RP\u0026mdash;root total phosphorus content; RK\u0026mdash;root total potassium content; BAC\u0026mdash;bacteria; FUN\u0026mdash;fungi; ACT\u0026mdash;actinomyces.\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e3.2 Interactive effect of organic materials and microbial inoculants on wheat biomass\u003c/h2\u003e\u003cp\u003eAmong all the biomass traits; shoot fresh/dry weight, and root fresh/dry weight responded significantly to the organic matters and microbial inoculant gradients individual and also under combined treatment of these materials (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The shoot fresh weight and dry weight was increased by 99.68% and 69.19%, respectively, under BC treatment (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea), which was highest value under BC1 treatment. This indicated that combined organic matters and microbial inoculants in BC had a significant impact on the shoot growth. The most intrigue results were obtained under MS5 treatment, which showed an increase of 505.60% and 568.32% in the root fresh weight and shoot dry weight, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). All these results recommended that organic matters and microbial inoculants synergistically promotes the wheat growth.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e3.3 Combined effect of organic materials and microbial inoculants on the soil physiochemical properties\u003c/h2\u003e\u003cp\u003eAmong the soil physicochemical properties, all parameters except pH; soil organic matter, total nitrogen (TN), available phosphorus (AP), and available potassium (AK) showed significant responses to organic materials (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). TN and AP also responded significantly to the microbial inoculant gradients, and TN, AP, and AK were significantly affected by the interaction between organic inputs and microbial inoculant levels. Soil pH showed no significant differences across treatments (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ea). Organic matter content increased under all combined treatments, with the highest increase observed in BC4 (117.12% over CK) (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eb). TN content increased in all treatments except WS3 and WS4, with BC3 showing the highest increase (65.48%) compared to CK (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ec). AP content was highest in the BC treatments, peaking under BC3 with a 34.17% increase over CK (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ed). AK content significantly increased across all treatments, with the greatest enhancement in BC5, showing a 121.50% increase compared to CK (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003ee).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e3.4 Effect of organic inputs and microbial inoculants on nutrient accumulation in wheat\u003c/h2\u003e\u003cp\u003eAll measured nutrient indicators including shoot and root nitrogen (N), phosphorus (P), and potassium (K) contents exception of shoot K content positively enhanced with the addition of organic materials and microbial inoculants individually, as well as combined (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Wheat under BC treatments showed the highest nutrient accumulation for N. Shoot N content were highest with an increase of 61.51% under BC3 compared to CK, while root N content was 29.47% greater in BC2 (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea). Shoot P content was 87.86% higher compared to CK under WS3. Root P content was 68.60% higher under BC5 (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb). Shoot K content showed no obvious differences among all these treatments; however, root K content increased 101.89% compared to CK substantially under BC5 (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\u003ch2\u003e3.5 The effect of organic materials and microbial inoculants on soil microbial population\u003c/h2\u003e\u003cp\u003eSoil microbial populations which include bacteria, fungi, and actinomycetes showed significant alterations in response to the addition of organic materials, microbial inoculants, and their interaction (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). BC treatments notably promoted bacterial abundance, with the population increasing consistently across inoculant gradients. The highest bacterial count was 266.27% compared to CK under BC5, (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea). The fungal populations were enhanced 610.20% compared to CK under WS treatments, with a maximum increase observed under WS5 (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eb). The MS5 treatment showed 361.64% growth of actinomycetes compared to CK (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ec), which supports the strategy to apply maize straws along with microbial inoculants results into the higher actinomycete proliferation.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003e3.6 Correlation and redundancy analysis of wheat traits under organic materials and microbial inoculant treatments\u003c/h2\u003e\u003cp\u003eRedundancy analysis indicated that physiochemical properties and microbial population of the soil and the growth indicators of wheat showed a total 50.12% variation, with a contribution of 35.62% for axis I and 14.50% for axis II (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). Correlation analysis showed significant associations between various growth and development indicators of wheat and soil nutrient status and microbial populations (Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). Results indicated that plant height, stem diameter, and leaf surface area all had highly significant positive correlations with shoot N and K content. Conversely, plant height and stem diameter were negatively correlated with shoot P content, indicating direct relationship between wheat growth parameters and nutritional status. A direct relationship between physiochemical properties of soil and wheat plant nutrient was found with the enhanced shoot N and K level in response to organic matter. Moreover, a positive correlations of bacteria, with the SPAD, leaf surface area, AP content, AK content, shoot N content, root P content, and root K content was observed. Additionally, a highly significant positive correlation of actinomycetes with shoot dry weight, root fresh weight and dry weight was also determined. However, negative correlations were observed among fungi and stem diameter, SPAD, shoot fresh weight, shoot N, and K content which indicated the close relationship of microbial populations with the soil physiochemical properties, plant biomass, and nutrient parameters (Fig. \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003e3.7 Comprehensive analysis of organic materials and microbial inoculants application\u003c/h2\u003e\u003cp\u003eAffiliation functional analysis revealed that biochar was the most effective treatment followed by the maize, and then wheat straw which was found to be the least effective treatment (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ea). Among all the treatments, the top five composite scores of wheat indicators under different treatments were ranked as BC3\u0026thinsp;\u0026gt;\u0026thinsp;BC5\u0026thinsp;\u0026gt;\u0026thinsp;MS5\u0026thinsp;\u0026gt;\u0026thinsp;BC4\u0026thinsp;\u0026gt;\u0026thinsp;BC2 (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003ea), indicating the highest score of 0.73 which was 193.87% higher compared to CK, under BC3 treatment,. Similarly, the soil traits were also analyzed under the organic materials and microbial inoculant agents. The effectiveness pattern was as ; BC3\u0026thinsp;\u0026gt;\u0026thinsp;BC2\u0026thinsp;\u0026gt;\u0026thinsp;BC4\u0026thinsp;\u0026gt;\u0026thinsp;WS5\u0026thinsp;\u0026gt;\u0026thinsp;BC5 (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eb). The highest score was 0.67 which was 331.25% compared to CK under the BC treatment, (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eb).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003e3.8 Structural equation modeling analysis\u003c/h2\u003e\u003cp\u003eAmong all explanatory variables, soil fungi had the greatest influence on wheat growth, contributing 41.7% to the model with a highly significant effect (P\u0026thinsp;\u0026lt;\u0026thinsp;0.002), followed by available potassium (AK, 21.8%), actinomycetes (18.7%), bacteria (6.8%), and available phosphorus (AP, 4.7%) (Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Fungi, AK, actinomycetes, bacteria and soil AP content were selected as the main environmental factors to analyze the effects of soil microbial populations and soil physiochemical properties on the growth of wheat through structural equation modeling. The different carbon sources negatively influence the fungi population in the soil which showed a positive effect on plant height, stem diameter, leaf surface area and SPAD of wheat (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ea, \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003eb, \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ec, \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ed). Secondly, plant height, stem diameter and leaf surface area of wheat was also enhanced with the modulation of AP and AK content in the soil (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ea, \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003eb, \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ec). Different carbon sources were positively correlated with shoot and root fresh weight of wheat (Fig. S2a, S2b). Different concentrations of microbial inoculant directly affected leaf surface area and root dry weight (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ec, \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ef). It was also found that different carbon sources also affected shoot N, P, K and root P, K content by affecting the fungal population in the soil (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003ea, \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003eb, \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003ec, \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003ee, \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003ef). Additionally, carbon sources also had a direct effect on root N, P content and root K content (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003ed, \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003ee, \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003ef). It was noteworthy that different concentrations of microbial inoculant also had a direct effect on shoot N, P, K and root Kcontent in wheat (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003ea, \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003eb, \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003ec, \u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003ef).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eRedundancy analysis of explanatory variables for differences in wheat growth indicators\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"4\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eExplanatory variable\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eContribution rate (%)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cem\u003eF value\u003c/em\u003e\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cem\u003eP value\u003c/em\u003e\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFUN\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e41.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e20.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.002\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAK\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e21.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e12.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.002\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eACT\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e18.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e13.3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.002\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eBAC\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e6.8\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e5.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.002\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAP\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e4.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e3.7\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.004\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTN\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e2.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e2.4\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.018\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003epH\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.6\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.11\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eOM\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e1.5\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e1.2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e0.288\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"4\"\u003eAbbreviations: pH\u0026mdash;soil pH; OM\u0026mdash;organic matter; TN\u0026mdash;total nitrogen; AP\u0026mdash;available phosphors; AK\u0026mdash;available potassium; BAC\u0026mdash;Bacteria; FUN\u0026mdash;fungi; ACT\u0026mdash;actinomyces.\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"4 Discussion","content":"\u003cdiv id=\"Sec17\" class=\"Section2\"\u003e\u003ch2\u003e4.1 Effects of organic materials and microbial inoculants on crop growth indicators\u003c/h2\u003e\u003cp\u003eCrop growth parameters are considered as the criteria to assess the crop development and productivity[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. In this study, we optimized four growth indicators under BC treatment, and variable concentrations of different microbial inoculant and found (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). Among all parameters of plant growth, plant height can be observed obviously and prominently and is closely related to crop yield[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. This study showed that plant height was enhanced by 8.23% and 8.44% after BC input compared to WS and MS, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea). Compared to straw, biochar has a porous structure and is rich in organic carbon, nitrogen, phosphorus, potassium and other beneficial nutrients which promotes plant height and leaf differentiation[\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. We found 0.81%-42.17% increase in leaf surface area as compared to CK, with the addition of biochar along with different concentrations of microbial inoculant (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). As a key indicator of photosynthesis, SPAD can directly affect the growth rate and yield of crops[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. However, this study showed that chlorophyll was lower under different organic materials along with microbial inoculants compared to CK (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec). Stem diameter reflects the structural strength and support capacity of the crop, and directly linked with the efficiency of nutrient uptake and transportation[\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. Biochar with different concentrations of microbial inoculant were effectively promoted the stem diameter by 13.74%-49.77% than CK (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed). Biochar improves soil structure, water retention and aeration, which helps to improve stalk thickness and length[\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec18\" class=\"Section2\"\u003e\u003ch2\u003e4.2 Effects of organic materials and microbial inoculants on biomass and nutrient accumulation\u003c/h2\u003e\u003cp\u003eShoot fresh and dry weights are collectively considered as crop biomass and also key indicators for assessing crop growth and yield[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Shoot fresh and dry weights were enhanced under the BC treatment (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea). This can be attributed to the optimization of the soil condition through the proper formulation of microbial inoculant, which promotes plant growth and consequently increases plant biomass[\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. Previous researchers have also reached the same conclusion through their studies on rice[\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. In this study, the results showed that both indicators were optimized with the three organic materials and microbial inoculants, but there were significant differences between treatments and microbial inoculant concentrations (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). Various crops have different responsive mechanisms with the addition and concentrations of fertilizers[\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. The total amount of nitrogen, phosphorus and potassium elements accumulated in the shoot of the plant, which are essential for plant growth, development and morphology[\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. Similarly, in this study, shoot N, P, and K levels varied significantly with the addition of different concentrations of microbial inoculant. In this study, the shoot P content was the lowest and shoot N content was the highest under BC treatment, while the opposite results were observed in WC treatment (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Biochar promotes soil microbial activity and increases the rate of nitrogen mineralization, thus increase the supply of effective nitrogen in the soil[\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Under WS treatment, the higher microbial population requires to decompose the straw and nitrogen availability, while the decomposition of organic acids promotes the efficacy of soil phosphorus, resulting in the lowest N content and the highest P content in shoot[\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Shoot N, P and K content in the subsurface also showed significant differences among the treatments, but most of the growth parameters were significantly promoted under the BC treatment (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Research showed that microorganisms in the microbial inoculants can promote the transformation and cycling of nutrients in the soil, and increase the biomass and nutrient level in the subsoil[\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec19\" class=\"Section2\"\u003e\u003ch2\u003e4.3 Effect of treatments on soil physicochemical properties\u003c/h2\u003e\u003cp\u003ePrevious studies have shown that soil physiochemical properties improve soil and crop root health, which ultimately promotes crop yield and quality[\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. Soil properties were optimized with the addition of BC treatment (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). Organic materials consists of different organic acids and minerals that helps to cope up the effects of environmental changes and also stabilize the soil pH, that\u0026rsquo;s why pH in the soil treated with organic materials and microbial inoculants did not differ much compared to the CK treatment (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea)[\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. Previous study has indicated that there are significant differences between the different organic materials and microbial inoculant gradients. The overall trend of growth parameters and microbial inoculant gradients is first increased and then declined[\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. This indicates that all treatments were significantly better than the CK treatment (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb). Therefore, the level of total nitrogen content is directly linked with the nitrogen supply capacity of the soil and crop growth conditions[\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. The optimized concentrations of microbial inoculant have a significant effect on soil nitrogen content and crop growth[\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. The TN content in this study was significantly increased with the addition of MS and BC compared to CK (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec). Previous studies have found that microbial inoculants can significantly alter the composition of soil microbial communities that helps to enhance the nitrogen fixation ability of soil, similarly with this study[\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. The TN content was significantly increased with the application of MS and BC compared to the CK (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ec). AP content varied considerably under different treatments (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ed), which may be related to the effects of soil physiochemical properties and differences in crop requirements. AK content can improve the disease resistance of crops and promote the crop growth[\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e]. Previous studies also showed that the highly aromatic structure and rich pore space of biochar provided ideal adhere and habitat sites for microorganisms, whereas, wheat and maize straw, despite the source of organic matter, had different effects on microbial activity and nutrient availability[\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. All these facts answers that why the AK content showed a negative correlation respective to the different levels of BC treatment, but a positive correlation in WS and MS treatments (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ee).\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec20\" class=\"Section2\"\u003e\u003ch2\u003e4.4 Response of soil microbial populations to organic inputs and microbial inoculant dsosages\u003c/h2\u003e\u003cp\u003ePrevious studies have shown that, soil microbial population is usually referred to the huge microbial communities such as bacteria, fungi, actinomycetes, in soil, which play a pivotal role in the decomposition of organic matter, recycling of nutrients, conversion of energy, and suppression of diseases soil[\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. There are significant differences in the performance of soil microbial populations under different treatment conditions. The results of this study showed that three microorganisms (bacteria, fungi, and actinomycetes) differed significantly among the different microbial inoculant doses as compared to CK. For instance, bacteria being the most abundant in the BC treatment, fungi in the WS treatment, and actinomycetes in the MS treatment (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e).The findings in this study are consistent with previous studies[\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. In addition, the study also showed that the dosing of different concentrations of microbial inoculant also significantly affected the changes in the microbial community[\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. The optimal efficacy of all these micoorganisms can be attained, when 100% concentration of microbial inoculant will be applied in the soil. However, research has demonstrated that elevated or diminished concentrations of microbial inoculant can exert negative effects on the microbial community[\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. Therefore, the appropriate concentrations of microbial inoculant are mandatory according to the specific soil type, crop requirements and developmental stages [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec21\" class=\"Section2\"\u003e\u003ch2\u003e4.5 Influence of microbial communities and carbon sources inputs on wheat growth and nutrient uptake\u003c/h2\u003e\u003cp\u003eElevated fungal populations in the soil inhibit plant height and chlorophyll content in wheat by reducing nutrient availability[\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e]. This study indicated that, alteration in fungal population were negatively correlated with wheat growth indicators (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ea, \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003eb, \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ec, \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ed). The different carbon sources indirectly affected plant height, leaf surface area and stem diameter of wheat by modifying the AP content in the soil (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ea, \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003eb, \u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ec). The application of different carbon sources might help to promote the phosphorus mineralization, which enhance phosphorus absorbance capability in by wheat, thus promoting growth and development[\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e]. Different carbon sources decrease the shoot fresh and dry weight by affecting bacterial and fungal populations (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003ee and S2). The underlying cause may be attributed to the competition between bacteria and roots for nutrients, as well as the impact of fungi on the conversion of organic matter and the availability of water nutrients[\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e]. Different carbon sources significantly affected the K content in shoot, whereas, and P and K level in root indirectly by regulating soil AK content. Conversely, N and P content in shoot and also N content in root was positively affected by regulating soil AP content (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e). Carbon sources not only directly influence the structure of microbial communities, but may also indirectly affect plant nutrient uptake by influencing soil nutrient cycling[\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e]. In addition to root N content, microbial inoculants had a significant effect on the shoot N, P content, and K content, as well as root P and K content in wheat plants with the altered fungal population in soil (Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e). Microbial inoculants alter the soil microbial environment and nutrient cycling, which in turn affects nutrient utilization of wheat [\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e, \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e].\u003c/p\u003e\u003c/div\u003e"},{"header":"5 Conclusions","content":"\u003cp\u003eThe optimized concentrations of microbial inoculant significantly increase the growth indicators and biomass of wheat, the nutrient level of the plant, moreover, improve physiochemical properties of soil, as well as the number and diversity of microorganisms in the soil compared with traditional fertilization treatments. Significant differences were found among the treatment groups with different carbon sources. Biochar with microbial inoculants was more effective as compared to the wheat and maize straw inoculated with the same microbial inoculants. The best recommended fertilization for enhanced shoot and root growth is the conventional fertilization along with the addition of biochar and optimized amount of Bacillus subtilis. Therefore, the application of different types of organic materials, especially the combined use of biochar and microbial inoculants, should be actively promoted in wheat production. This combined application will not only help to improve the yield and quality of crops, but also the soil ecosystem which promote the development of sustainable agriculture.\u0026nbsp;\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthorship contribution statement\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMiao Wang: experiments, investigations, methods, software, visualization, writing-preliminary drafts, writing-commentary and editing. Chi Zhang: experimentation, investigation, methods, software, visualization, writing-preliminary draft, writing-commenting and editing. Hong Wang: research, writing-commenting and editing. Li Wang: experiments, investigations, methods. Rufang Zhang: conceptualization, funding acquisition, project management, research, writing-commenting and editing. Xuguang Li: situation analysis, research, writing-criticism and editing. Xin-Xin Wang: experimentation, methodology, software, research, writing-criticism and editing.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of Data and Materials\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe original data supporting the conclusions of this paper will be provided by the author without reservation, and data is provided within the supplementary information files.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThere was no requirement to seek ethical approval to carry out the work described above.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of competing interest\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was fnancially supported by National Key R\u0026amp;D Program of China (2021YFD1901001).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe would like to acknowledge reviewers and editors for their time and constructive feedback,which·will undoubtedly enhance the quality of·this manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eMoodley V, Phophi MM, Mafongoya PL. 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Transactions of the Chinese Society of Agricultural.\u003cem\u003e \u003c/em\u003e2025:1-12.\u003c/li\u003e\n\u003cli\u003eMuhammad I, Shahid RM, Muhammad S, Sami UA, Ahmad S, Abdul S, Liaqat A, Allah D, Balal Y. Biochar reduced cadmium uptake and enhanced wheat productivity in alkaline contaminated soil. International Journal of Agriculture and Biology.\u003cem\u003e \u003c/em\u003e2020, 24(6):1633-1640.\u003c/li\u003e\n\u003cli\u003eYang S, Lan SX, Ming QZ, Gen WL, Qi HJ, Feng ZH, Fei ZY, Yang DH, Jun XL. Effects of synergistic intensification of straw return on soil quality and rice growth by rotting agent and biochar on soil quality and rice growth. Acta Agriculturae Zhejiangensis.\u003cem\u003e \u003c/em\u003e2025:1-11.\u003c/li\u003e\n\u003cli\u003eParul C, Anita S, Anuj C, Priyanka K, Saurabh G, Damini M. Illumina based high throughput analysis of microbial diversity of maize rhizosphere treated with nanocompounds and \u003cem\u003eBacillus\u003c/em\u003e sp. Applied Soil Ecology.\u003cem\u003e \u003c/em\u003e2021, 159:103836.\u003c/li\u003e\n\u003cli\u003eV, Hansen L, Bonnichsen I, Nunes K, Sexlinger S, R. Seed inoculation with \u003cem\u003ePenicillium bilaiae\u003c/em\u003e and \u003cem\u003eBacillus simplex\u003c/em\u003e affects the nutrient status of winter wheat. Biology and Fertility of Soils. 2020, 56(1):97-109.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"bmc-plant-biology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"pbio","sideBox":"Learn more about [BMC Plant Biology](http://bmcplantbiol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/pbio/default.aspx","title":"BMC Plant Biology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"biochar, straw, microbial inoculants, wheat growth, soil improvement","lastPublishedDoi":"10.21203/rs.3.rs-7018728/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7018728/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe study examined the differences in wheat plant growth and soil traits under different treatments of organic materials and microbial inoculants. To explore the effects of different carbon sources and microbial inoculants on wheat growth and soil improvement, a two-factor randomized block design experiment was conducted with conventional fertilization as the control (CK). The pot experiment involved co-application of conventional fertilization with different organic materials (wheat straw (WS), maize straw (MS), and biochar (BC)) and various concentrations of microbial inoculant (0, 2.50, 5.00, 7.50, and 10.00 ml per pot). The results showed that compared to CK, the total nitrogen, available phosphorus, and shoot total nitrogen content in wheat were significantly increased by 65.48%, 34.17%, and 61.51%, respectively, under the BC3 treatment (conventional fertilizer\u0026thinsp;+\u0026thinsp;31.61 g of biochar\u0026thinsp;+\u0026thinsp;5.00 ml of bacillus subtilis bacillus). The available potassium, phosphorus, potassium, and bacterial count in roots were significantly increased by 121.50%, 68.60%, 101.89%, and 266.27%, respectively, under the BC5 treatment (conventional fertilizer\u0026thinsp;+\u0026thinsp;31.61 g of biochar\u0026thinsp;+\u0026thinsp;10.00 ml of bacillus subtilis bacterial agent). According to the effectiveness results of different combinations, it was found that BC3 treatment achieved the highest score. In addition, the results of structural equation modeling indicated that different carbon sources and microbial inoculants formulations indirectly affected wheat growth by regulating the soil microbial community and the soil physiochemical properties. In conclusion, biochar with microbial inoculants was found to be the most effective in enhancing wheat growth and synergistically improving soil physiochemical properties.\u003c/p\u003e","manuscriptTitle":"Integrated effects of organic amendments and microbial inoculants on soil quality and wheat growth performance","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-15 17:46:22","doi":"10.21203/rs.3.rs-7018728/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"editorInvitedReview","content":"","date":"2025-07-30T23:42:02+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-24T13:39:06+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-21T14:54:26+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"258030291621682867083403817794195119645","date":"2025-07-20T14:07:23+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"107036026237739564687155944504894033538","date":"2025-07-20T06:32:17+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"292162813107444741640051311114228364569","date":"2025-07-18T21:21:55+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-07-17T16:14:11+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"221173122914025471506005454905908717043","date":"2025-07-15T15:26:47+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"193333713862626680944678653199814805978","date":"2025-07-15T11:05:05+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"150169103619551782622956152330525737328","date":"2025-07-14T12:20:48+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"250261120052341661010258524496079512423","date":"2025-07-14T09:36:09+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"164322678223417011733532463964881453365","date":"2025-07-14T04:45:46+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"145920280945708371002381950977472888130","date":"2025-07-14T00:25:53+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-07-13T21:20:22+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-07-04T11:41:26+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-07-04T11:40:59+00:00","index":"","fulltext":""},{"type":"submitted","content":"BMC Plant Biology","date":"2025-07-01T09:29:21+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"bmc-plant-biology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"pbio","sideBox":"Learn more about [BMC Plant Biology](http://bmcplantbiol.biomedcentral.com/)","snPcode":"","submissionUrl":"https://www.editorialmanager.com/pbio/default.aspx","title":"BMC Plant Biology","twitterHandle":"BMC_series","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"em","reportingPortfolio":"BMC Series","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"1365e3c7-9d32-49bb-a9ec-a5f5dad30036","owner":[],"postedDate":"July 15th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2025-07-15T17:46:22+00:00","versionOfRecord":[],"versionCreatedAt":"2025-07-15 17:46:22","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7018728","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7018728","identity":"rs-7018728","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}