Comparative study on Organic Composts in Blueberry: Insights into Soil Physicochemical Properties and Heavy Metal Control

Comparative study on Organic Composts in Blueberry: Insights into Soil Physicochemical Properties and Heavy Metal Control | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Comparative study on Organic Composts in Blueberry: Insights into Soil Physicochemical Properties and Heavy Metal Control Hao Tang, Ying Dai, Lijuan Tang, Juan Guo, Ke Wen, Fangke Yuan, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7058481/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 09 Jan, 2026 Read the published version in Environmental Geochemistry and Health → Version 1 posted 4 You are reading this latest preprint version Abstract Organic fertilization is an essential method for sustainable agricultural development. Composts of edible fungal substrates (CEFS) and Chinese herbal residues (CCHR) are potential ecological organic fertilizers, but rarely used in blueberry cultivation. The purport is to compare different fertilizations on the integrated soil fertility (ISF), nutrients availability, and the heavy metals (HMs) risks in the blueberry soil and fruit; simultaneously to clarify the relationships between nutrients input and HMs risks for the blueberry. In this study, we conducted a field trial using CEFS and CCHR in blueberry, comparing to the special fruit organic fertilizer in the market (SFOF) and potassium sulfate compound fertilizers (PSCF). Results showed that the ISF of blueberry was mostly affected by the input of nitrogenous and organic matters, and restricted by HMs. CEFS and CCHR demonstrated a better fertility and heavy-metal prevention efficiency comparing to SFOF and PSCF. But excess organic matters in soil would affect blueberry's absorption of potassium, it is necessary to replenish potassium fertilizer in time for blueberry. Our results would provide a theoretical basis for the application of CEFS and CCHR in the safety production of blueberry. Organic composts soil fertility plant performance heavy metals Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 1. Introduction` Industry and chemical fertilization aggravate heavy metals (HMs) pollution, which is unfavorable for cash crops, especially for blueberry (El Mujtar et al. 2019 ). Belonging to Ericaceae taxonomically, Vaccinium , blueberry is rich in anthocyanin, polyphenols and other nutrients (Correa-Betanzo et al. 2014 ). Study suggested that the global blueberry production was 1,934,400 tons in 2021, increased by 183.31% than 2018, and it has been selected for poverty alleviation in mountainous regions ( http://www.fao.org/faostat/en/#data/QC ). However, excessive chemical fertilizers increased bioavailability of soil HMs, accelerated the accumulation in blueberry fruits through competition with nutrient channels, and decreased the quality of blueberry to threat people's health (Wu et al. 2023 ). Moreover, for lacking of root hair, blueberry mainly absorbs nutrients through Ericoid Mycorrhizae, but that responses sensitively to chemical fertilizers (Carrillo et al. 2015 ), while keeps an affinity to substantial organic sediments (Smagula et al. 2008). Therefore, it is practicable to substitute chemical fertilizers with organic sediments in sustainable production of blueberry. With an annual output of millions of tons, the edible fungal substrate (EFS) and Chinese herbal residue (CHR) are two typical secondary biomass wastes (Chen et al. 2020 ). Not been fully recycled, those waste materials have caused a series of environmental problems and needed for an urgent disposal in China (Holroyd et al. 2012). Organic composting is regarded as a good method to solve it (Bertoldi et al. 2016 ). As reported, Composts of edible fungal substrate (CEFS) and Chinese herbal residue (CCHR) are all rich in organic acids, nitrogen, potassium and other beneficial nutrients for plants (Leopold et al. 2005 ). And CEFS could counteract the pH-depressing effect induced by chemical fertilizer (Stewartd. et al. 1998). Moreover, the CCHR of Isatis tinctoria significantly reduced the bioavailability of Cu and Cd by fixation adsorption and precipitation formation (Ma et al. 2020 ). Thus, it is feasible and environmental-friendly to apply them in crop fertilization. The two composts were proved on many crops like watermelon, grape and so on, both biomass and fruit quality were improved effectively (Feldman et al. 2000 ; Mugnai et al. 2012 ). But there are few studies focused on the application in blueberry, and neither know the fertilization effects in contrast with conventional fertilizers. Hence, we conducted a field trial to compare the fertilization effects of CEFS and CCHR with conventional fertilizers in blueberry. The objectives of this work were (ⅰ) to compare different fertilizations on the integrated soil fertility (ISF) and the nutrients availability; (ⅱ) to reveal different fertilizations on the heavy metal risks in the blueberry soil; (ⅲ) to assessment the bioavailability of Cadmium (Cd) in soil and its concentrations in blueberry fruit with different fertilizations; (iv) to clarify the relationships between nutrients input and heavy metal risks for the blueberry. The findings of this work would provide helpful information for fertilizing in soil properties and blueberry growth, and offer scientific references to the sustainable and safety production of blueberry. 2. Materials and Methods 2.1 Material Preparation CEFS and CCHR were prepared by hyperthermal composting and fermentation according to the methods of Meng (Meng et al. 2018 ). Firstly, crushed the raw materials (Table S1 ) to a particle size of 40 mm, then accumulated the particles into small trapezoidal hills (top length 3 m, bottom length 5 m, height 2.5 m, width 1.5 m) in a composting greenhouse. Secondly, kept the temperature above 50 ℃ for 70 days, then cooled naturally and fermented for 48 days. Finally, further removed impurities and undecomposed organic matter, the refined compost after treatment had a water content of about 30% and a carbon nitrogen ratio of 15–20. The content of HMs meets the national standards (GB/T 23349 − 2009). The conventional fertilizers were purchased in the comprehensive market, including the special microbial fruit organic fertilizer popularly used (SFOF) and the potassium sulfate compound fertilizers (PSCF). 2.2 Experimental Design The trial was conducted in a blueberry garden of Sichuan Agricultural Science Academy in Qingbaijiang, Chengdu (30º52´01"N, 104º18´47"E). The local climate belongs to the Subtropical monsoon humid climate with an annual temperature of 14.9–16.7 ℃. The background soil characteristics are listed in Table 1 . A randomized complete block was designed for 8 fertilization treatments, each of which contained 3 fertilization plots, and per plot contained 3 rows of "Gardenblue" ( Vaccinium ashei Reade) (Fig. 1 ). An equal-nitrogen fertilization method of an annual nitrogen rate at 18 g·m − 2 ·a − 1 was implemented referring to Mohsan (Mohsan Zafar et al. 2007). The experiment was repeated thrice respectively in 2022 to 2024, for details referring to Table 2 . Table 1 Background properties of fertility and HMs in the blueberry soil Units: mg·kg − 1 properties values properties values properties values pH 6.4 ± 0.2 SOM 37100 ± 1500 A-Cr 15 ± 2.5 TN 1610 ± 310 CEC 13.7 ± 1.5 Cd 0.49 ± 0.05 TP 1092 ± 120 Cu 39.7 ± 3.7 A-Cd 0.17 ± 0.03 TK 15000 ± 984 A-Cu 5.3 ± 0.5 S-Cu 150 AN 165 ± 21 Ni 31.7 ± 2.9 S-Ni 70 AP 51.1 ± 8.5 A-Ni 4.1 ± 0.6 S-Cr, I-Cr 150, 850 AK 86 ± 13 Cr 80.8 ± 7.5 S-Cd, I-Cd 0.3, 2 Note: A refers to available fraction of elements; S and I refer to screening and intervention standard of HMs. Table 2 Different fertilization treatments and dosages for each growth period Treatments (equivalent N of 18 g·m − 2 ·a − 1 ) Fertilization patterns Primary fertilization (g·m − 2 ) Florescence fertilization (g·m − 2 ) Fruit bearing fertilization(g·m − 2 ) Fruit swelling fertilization(g·m − 2 ) Fertilization time Nov. 20, 2021 Nov. 25, 2022 Jan. 22, 2022 Jan.26 2023 Mar. 17, 2022 Mar. 15, 2023 May 21, 2022 May 27, 2023 Nov.18, 2023 Jan.22 2024 Mar. 20, 2024 May 30, 2024 CK NF 0 0 0 0 T1 CEFS 416 208 104 104 T2 CEFS + PSCF 208 + 45 104 + 22.5 52 + 11.25 52 + 11.25 T3 CCHR 225 112.5 56.25 56.25 T4 CCHR + PSCF 112.5 + 45 56.25 + 22.5 28.13 + 11.25 28.13 + 11.25 T5 SFOF 128 64 32 32 T6 SFOF + PSCF 64 + 45 32 + 22.5 16 + 11.25 16 + 11.25 T7 PSCF 90 45 22.5 22.5 Note: NF: not fertilized; CEFS: organic composts of edible fungal substrates; PSCF: potassium sulfate compound fertilizers; CCHR: organic composts of Chinese herbal residues; SFOF: special organic fertilizer fruit in market; PSCF: potassium sulfate compound fertilizers. 2.3 Sampling and Analysis Fresh soil samples in 0–20 cm rhizosphere of each plot were collected by five point sampling method according to Xie (Xie et al. 2015 ). After naturally air dried and homogenized, the soils were sieved through 2-mm mesh in the laboratory to determine the physicochemical properties. Soil pH was measured by pH meter (SevenCompact-s210) in a soil suspension (ratio of soil: water (w/v) was 1: 2.5). The total nitrogen (TN), phosphorus (TP), potassium (TK) were respectively determined by Kjeldahl method (Nozawa et al. 2005 ), sodium hydroxide alkali melting molybdenum antimony anti-colorimetry (Gonzalez et al. 2019 ), and acid melting flame photometry (Burr 2019 ). The alkali hydrolyzed nitrogen (AN), quick available phosphorus (AP), and effective potassium (AK) were tested by the alkali dissolving diffusion method (Shuai et al. 2019 ), 0.5 mol·L − 1 sodium bicarbonate extraction method (Liu et al. 2011 ), and 1 mol·L − 1 ammonium acetate extraction flame photometry (Qiu et al. 2018 ), respectively. In addition, the Potassium dichromate heating method was used for soil organic matter (SOM) determination (Gerenfes et al. 2022 ), while the sodium acetate sodium chloride exchange method for cation exchange capacity (CEC) measurement (Millar et al. 2017 ). The concentrations of Cu, Ni, Cr, Cd were determined by atomic absorption spectroscopy while their availability were evaluated by the toxicity characteristic leaching procedure (TCLP) (Moon et al. 2018 ). The fractions of HMs containing HOAc-extractable, reducible, oxidizable, residual were analyzed by BCR sequential extraction method (Wu et al. 2018 ). The degree of soil contamination risk was divided by the national standard of China (GB15618-2018), in which the screening and intervention thresholds are applied for evaluating the threats to the quality and safety of agricultural products, growth of crops, and soil ecological environment(Chen et al. 2021 ). The pollution risks were evaluated by the Nemerow comprehensive pollution index (NPI) as Table S2 (Moghtaderi et al. 2018 ), and the classification criterions for NPI was executed as Table S3 . 2.4 Data Analysis and Graphing The mean values and standard deviations of all data originating from three replicates in this study were calculated. Considering the numerous and complicated factors on soil nutrient, integrated soil fertility (ISF) is often introduced to evaluate soil quality (Getachew et al. 2017). The evaluation of ISF was based on the factor score analysis model according to the Principal Component Analysis (PCA) via SPSS (Xie et al. 2015 ). The calculation formulae were designed in Table S4. Table S5 to S7 presented the computation process of integrated soil fertility (ISF), in which data standardizastion, dimension reduction analysis, determination of principal component coefficients and ISF equation construction included. Statistical significance was determined by one-way ANOVA in SPSS18.0 software using least significant difference (LSD) method to compare the mean values of each sample at a significant level of p < 0.05. All values were described using Origin 9.1 software in this paper. 3. Results 3.1 Changes of Integrated Soil Fertility and Nutrients Availability in the soil The integrated soil fertility (ISF) with fertilization is showed in Fig. 2 . The ISF in T2 (CEFS + PSCF) and T3 (CCHR) increased by 149.31% and 139.71% than CK significantly, manifesting the highest fertility. When applied the three organic fertilizers individually, the ISF was T3(CCHR) > T5 (SFOF) > T1(CEFS), while the combination efficiency with PSCF was T2 (CEFS + PSCF) > T4(CCHR + PSCF) > T6 (SFOF + PSCF). Fertilization effects on nutrients availability was showed in Fig. 3 . The available nitrogen (AN) in T1 increased by 5.94% than CK, while the other treatments were all decreased. And the available phosphorus (AP) in T2, T4, T6 were increased, with the others decreased comparing to CK. And the availability of potassium (AK) in all fertilized treatments was improved by 39.40%-140.91% than CK. 3.2 Assessment of Heavy Metal Risks in the Soil The heavy metals (HMs) pollution degree of the garden before fertilization was manifested in Fig. 4 , that based on the screening and intervention standards from the Ministry of Ecology and Environment, P. R. China (GB15618-2018). Results showed that the screening risks of Cu, Ni, Cr were 26.51%, 45.3%, 53.88%, respectively. But the screening risk coefficient of Cd was up to 163.33%, while its intervention risk was 24.5%. Error bars manifested the change amplitude of different HMs pollution indexes, which indicated that the changing range of the four HMs was Cd > Cr > Ni > Cu. The HMs concentrations and the corresponding Nemerow integrated contamination index (NPI) with fertilization were listed in table S8 and S9. The background NPI before fertilization was 1.26. According to Fig. 5 , the NPI in CK (not fertilization) was 1.45 (slight pollution level), and that in T3 (CCHR) decreased by 32.41%, significantly. Though there were no significant differences among T1 (NPI = 1.22), T2 (NPI = 1.5), T4 (NPI = 1.35), T5 (NPI = 1.59), but T1 was still preferable in reducing the risks. However, an apparent risk elevation was recorded in T6 (NPI = 1.85) and T7 (NPI = 2.16), whereas T7 was regarded as a moderate pollution (2 < NPI ≤ 3) notably. 3.3 Bioavailability of Cd in the Soil and its Concentrations in the Fruit We compared the fractions of Cd in the soil and its concentrations in the fruit to assessment the bioavailability of Cd with fertilization (Fig. 6 and Fig. 7 ). Compared with CK, T1, T3 decreased HOAc-extractable Cd by 39.37% and 23.94%, whereas T5 and T7 increased it by 23.30% and 23.41%. All treatments with organic composts (T1-T4) cut down the HOAc-extractable Cd by 9.87–44.45%, and T1, T2 further reduced the reducible Cd by 11.07, 33.51%. The organic composts (particularly in T2, T3) were also advantageous to the increase of residual Cd. Figure 7 showed that the concentrations of Cd in all treatments were less than 0.05 mg·kg − 1 (the national food safety standards). Compared with CK (not fertilization), Cd concentrations of blueberry fruit in T1(CEFS), T3 (CCHR) were reduced significantly at p < 0.05 level. At the same time, that in T6 (SFOF + PSCF), T7 (PSCF) were increased significantly (p < 0.05), and the rest treatments showed no significant differences. 3.4 Relationships between Nutrients Input and HMs Risks Correlation matrix in Fig. 8 illustrated the relationships between the nutrients input and the HMs risks. The soil fertility is positively relevant to principal nutrients with a relevance of N > P > SOM > K, where N input was significantly correlated at 0.05 level. The correlation coefficient between the input of P and N was 0.761, and 0.726 between the input of P and K (p < 0.05). The SOM input was positively related to the ISF, and the input of N and P, while adverse impact on K. The ISF was negatively related to all HMs, especially to Cu (p < 0.01), but was relatively lower relevant to Cd. Risks of the four HMs was all negatively correlated with the SOM input. According to the RDA analysis in Fig. 9 , the distribution of T1, T2, T3, T4 were consistent with the main soil elements (TN, TP, AK, AN, AK and SOM). And the distribution of CK, T5, T6, T7 were deviated from the main nutrient elements. But for the pollutants in the soil (Cu, Ni, Cr, Cd), the distribution trends were opposite. 4. Discussion 4.1 Fertilization Effects on Integrated Soil Fertility and Nutrients Availability for blueberry Trial results indicated that T2 (Composts of edible fungal substrate + the potassium sulfate compound fertilizers, CEFS + PSCF) and T3 (Composts of Chinese herbal residue, CCHR) manifest the highest fertility, mainly because the fungal residues in the organic compounds increased the content of microbial biomass, supplied more dissolved organic carbon (C) and nitrogen (N) for the soil (Paredes et al. 2016 ). When applied the three organic fertilizers individually, the integrated soil fertility (ISF) was T3(CCHR) > T5 (the special microbial fruit organic fertilizer popularly used, SFOF) > T1(CEFS), which meant CCHR was better for fertility improvement. The combination efficiency with PSCF was T2 (CEFS + PSCF) > T4(CCHR + PSCF) > T6 (SFOF + PSCF), which meant CEFS and CCHR were better for fertility retention. It means that the combining fertility of the conventional and chemical fertilizers was not as good as the combination of organic and chemical fertilizers. Previous studies also mentioned that the combination of Chinese herbal residue and potassium sulfate compound (T4) could increase the activity of urease and phosphatase (P) to accelerate the decomposition of urea and insoluble phosphorus in soil (Chang et al. 2014 ), thereby improving the ISF. But in T6, the application of PSCF weakened the ISF, mainly because chemical fertilizer disturbed the soil microflora in the microbial organic fertilize (SFOF), and restricted the microbial metabolic activity, which correspondingly decelerated the decomposition and circulation of nutrients in the soil (Gu et al. 2019 ). Therefore, it is feasible to apply CEFS and CCHR to replace conventional fertilizers for a better nutrient supply in blueberry cultivation. In all treatments, T1 could elevate the Available Nitrogen (AN), which mainly because that the fungal residue provided more carbon sources for microorganism to accelerate the secretory of extracellular depolymerase, thus benefited the mineralization of organic nitrogen (Pacheco et al. 2017 ). But when combined with inorganic fertilizer, more urea in PSCF decreased the C/N ratio of soil, which inhibited cellulose decomposing bacteria and reduced the release of AN in fungal residue (Ostrowska et al. 2015 ). The available phosphorus (AP) in T2, T4, T6 increased than CK, mainly because more organic matters in soil kept more moisture, accelerating the dissolution and migration of mineral phosphorus to root system (Moorberg et al. 2015 ). As for potassium (K), its availability in fertilized treatments was overall improved, because fertilization increased the special adsorption sites (K X ) to raise the release power of soil K + (Sharma et al. 2013 ). But the application of CCHR (T3, T4) was still the best, mainly because of the attachment to potassium ions by the Chinese medicine residues. Research has shown that traditional Chinese medicine residue compost contains the strain DGNK-JJ1, which has strong effect on potassium hydrolysis. This strain is of fibrotic fiber microorganism ( Cellulose microbium cellulans ), which has nitrogen fixation, produces β -1,3-glucanase, chitinase, and can degrade monocyclic aromatic hydrocarbons and release K + (Dou et al. 2019). During the growth period of blueberry, Nitrogen is an important element for the plant growth and leaf development, Phosphorus can promote cell division and enlargement of blueberry fruits, and Potassium is for fruit coloring, anthocyanin synthesis and sugar metabolism (Wu et al. 2021 ). Therefore, the application of Composts of edible fungal substrate and Chinese herbal residue can promote nutrient availability and macro-elements supply to soil, thereby increasing the yield and quality of blueberries. 4.2 Fertilization Effects on heavy metal pollution risks for blueberry As for the heavy metal pollution risks, when the content of soil pollutants is not greater than the screening standard, the pollution risk of farmland can be generally ignored. When it is between the screening and intervention values, there may be pollution risks, collaborative monitoring and safety utilization measures should be adopted. When it is higher than the intervention values, edible crops are prohibited to cultivate as result of high contamination risks in soil (Lu et al. 2023 ). According to our investigation (Fig. 4 ), screening risks of Cu, Ni, Cr were 26.51%, 45.3%, 53.88%, respectively, which meant there was no pollution risk of the three HMs in this blueberry garden. But considering the heavy industry in Qingbaijiang, the potential contamination risks can’t still be overlooked. However, the screening risk coefficient of Cd was up to 163.33% while its intervention risk was 24.5%, which meant special attention should be paid to this element, may ascribing to the relatively high background value of Cd in the northeast of Chengdu plain (Deng et al. 2019 ). In addition, error bars on the columns manifested the change amplitude of different HMs pollution indexes, which indicated that the changing range of the four HMs was Cd > Cr > Ni > Cu. It was reported that Cd was most easy to be affected by human activities (Laxmi et al. 2022), so Cd deserved more attention for the safety production in the blueberry garden. In terms of the Nemerow comprehensive pollution index (NPI), the background value before fertilization was 1.26, defining as a slight pollution level according to the classification criterions in Table S3 (Yang et al. 2011 ). According to Fig. 5 , the NPI in CK (not fertilization) was 1.45 (slight pollution level), which was higher than the background value before fertilization. It showed that there exist exogenous HMs input to the garden. As located in an industrial zone, careless management could accumulated much more HMs because of various human activities such as fossil fuel combustion, automotive exhaust emission, refuse burning and wastewater irrigation (Tang et al. 2018). The contamination risk in T3 (NPI = 0.98) was significantly abated by 32.41% compared to CK, which achieved to the non-pollution level (0 < I ≤ 1), indicating CCHR was best in HMs risks reducing. Besides, the NPI of T1 among the other organic treatments (T1-T6) was still lower (NPI = 1.22), indicated that CEFS was also relatively better in reducing the risks. It is reported that organic fertilization has passivation effect on HMs by the intrinsic components of fertilizers, and organic matters are favorable to the valence reduction and detoxification of HMs (Alam et al. 2020 ). And organic materials could stimulate the activities of soil enzymes and improving bacterial abundance to relieve stress of HMs (Liu et al. 2020 ). Both edible fungal substrate and Chinese herbal residue contain rich organic matter, whose composts (CEFS, CCHR) have good effects in improving microbial activity and inhibiting heavy metal migration for blueberry soil. But high concentrations of HMs in chemical fertilizers could restrain the growth of soil microorganism like bacteria, fungi and actinomycetes (Zhang et al. 2024 ). That’s why an obvious elevation of the risks was recorded in T6 and T7. Therefore, composts of edible fungal substrate and Chinese herbal residue could reduce the comprehensive pollution risks of heavy metals in blueberry planting. 4.3 Fertilization Effects on Bioavailability of soil Cd and Fruit safety of blueberry Given the intervention risk of Cd in the soil was 24.5%, special attention should be paid to this element, we analyzed bioavailability of the soil Cd and safety of the blueberry fruit. Residual and oxidizable forms of HMs are thought as relative stable while reducible and HOAc-extractable forms as instable (Peng et al. 2019 ). Compared with CK, T1, T3 decreased HOAc-extractable Cd by 39.37% and 23.94%, whereas T5 and T7 increased it somewhat (Fig. 6 ). Meanwhile, all treatments with organic composts (T1-T4) cut down the HOAc-extractable Cd by 9.87–44.45%, and T1, T2 further reduced the reducible Cd by 11.07, 33.51%. Therefore, CEFS (T1) and CCHR (T3) manifested the best immobilization effect on Cd, mainly because the intercellular deposition of passivation bacteria and the complexation of SOMs (Fang et al. 2024 ). The combination of PSCF improved the HOAc-extractable Cd, mainly due to the chemical fertilizer could lead to a higher Cd accumulation in plants (Liu et al. 2017 ). Furthermore, compared with CK (not fertilization), Cd concentrations of blueberry fruit in T1(CEFS), T3 (CCHR) were reduced significantly at p < 0.05 level (Fig. 7 ), while that in T6 (SFOF + PSCF), T7 (PSCF) were significantly increased, and the rest treatments showed no significant differences. Though the concentrations of Cd in all treatments were not exceeding the limitation of fresh fruit (Cd < 0.05mg·kg − 1 ) according to the national food safety standards in China (GB 2762 − 2017), the organic fertilizers could further reduce the accumulation of HMs in fruits. This was in similarity with the concentration of available Cd in soil, owing to the passivation effect to Cd by CEFS and CCHR. That is, composts of edible fungal substrate and Chinese herbal residue can reduce the available state of soil Cd to lower the Cd content in the plant, thereby ensuring the safety of blueberry fruits. Therefore, it is necessary to substitute composts of edible fungal substrate and Chinese herbal residue for chemical fertilizers in safety production of blueberry. 4.4 Comprehensive Effects of Fertilization on Blueberry According to the correlation analysis, we found the integrated soil fertility (ISF) of blueberry was mostly affected by the input of N. In growth periods of blueberry, N is the most important element in blueberry leaves for synthesis of soluble sugar, anthocyanin, flavonoids, total phenols and adjusting the fruit width and yield (Bryla et al. 2012 ). Similarly, we found the input of P was significantly interrelated with N input, while P input significantly affected the amount of K as well. Usually throughout the entire growth period of blueberry, the requirements ratio of N, P, K is 4:1:2, ‘N determines P, K’is widely recognized as a fundamental principle of blueberry fertilization (Emmanuel et al. 2016 ). That’s why we adopted an equal-nitrogen fertilization method to compare different fertilization effects in this article. In addition, SOM input was also positive related to ISF, which is in similarity with previous study that SOM was regarded as the ultimate determinant of soil fertility for adjusting soil bulk density, water holdup, aggregation, root penetration and compaction (Chalise et al. 2018 ). As far as the relationships between principal nutrients, the input of SOM had a positive effect on the input of N and P while adverse impact on K, which are in line with previous studies (Lewis et al. 1991 ). But because potassium was majorly supplied by chemical fertilizer (PSCF), that’s why CEFS + PSCF, CCHR + PSCF obtained the relative higher ISF scores in our experiment. Regarding up to 90% of soil N is held in SOM in an organic form (Nguyen et al. 2011), by which positively and negatively affected the adsorption intensity of P and K respectively (Hongwen Sun et al. 2008). So, when we apply organic fertilizers to blueberry, we need to supplement potassium fertilizer in time. We can consider replacing nitrogen and phosphorus fertilizers by organic composts while combining exogenous potassium fertilizer in blueberry cultivation. On the other hand, the ISF was negatively related to all HMs, might be attributed to HMs reducing nutrients maintenance, such as decelerating N mineralization by inhibition of microbial activity (Babich et al. 1985), or reducing P, K adsorption by occupying part of the adsorption sites in soil colloids (Zhang et al. 2021 ). The ISF was negatively related to Cu (p < 0.01), but was relatively lower relevant to Cd, mainly because of the lower resolution rate and lower mobility of Cu 2+ in soil than Cd 2+ (Cavallaro et al. 1980), thus much more Cu 2+ would remain in the soil rather than flowing with the root absorption and microbial driving. As a result, the immobilization of Cd in soil-plant system deserved more attention. In addition, SOM input was also negatively correlated with the risks of the four HMs, mainly because the chelation of organic matters reducing bioavailability of HMs (Boominathan et al. 2003), which may provide theoretical basis for usage of organic composts in blueberry garden to reduce HMs pollution risks. According to the RDA analysis in Fig. 9 , the treatments of T1, T2, T3, T4 obtained more effective N, P, K and SOM, while suffering less HMs pollution from Cu, Ni, Cd, Cr. On the one hand, organic composts can increase soil humus content, improve soil aggregate structure, and enhance soil water and fertilizer retention capacity. On the other hand, organic composts can provide more carbon sources to stimulate microbial activity and promote the transformation of heavy metal forms, and reduce the bioavailability of soil HMs. That is, the organic-fertilization treatments of CEFS and CCHR could bring superior comprehensive fertilization efficiency and less pollution for blueberry. However, non-fertilization or the application of inorganic fertilizers (SFOF and PSCF) may have an adverse effect. 5. Conclusions This study revealed that there were some nutrients deficiency and heavy metals (HMs) pollution risks for blueberry in the northeast plain of Chengdu. According to our study, we found the integrated soil fertility of blueberry was mostly affected by the input of nitrogenous and organic matters. Composts of edible fungal substrates and Chinese herbal residue were beneficial to increase soil organic matter content and promote nitrogen mineralization, thereby improving the soil fertility and nutrient supply for blueberry. But we found excess organic matters in blueberry soil would affect the release of potassium ions, it is necessary to replenish potassium fertilizer in time for blueberry. In addition, we found the integrated soil fertility was suppressed by heavy metals in the soil, especially cadmium, which reducing nutrients maintenance by decelerating Nitrogen-mineralizing microorganisms and occupying the adsorption sites of P, K in the soil colloids. But composts of edible fungal substrates and Chinese herbal residues could provide sufficient organic matter for the soil, and reduce the bioavailability of heavy metals through chelation, which effectively safeguarded the security of blueberry fruit. In a word, comparing to the Special Microbial Fruit Organic Fertilizer commonly used in the market and Potassium Sulfate Compound Fertilizer, compost of edible fungal substrates and Chinese herbal residues demonstrated a better fertility and heavy-metal prevention efficiency. Furthermore, in terms of the comprehensive effect of improving soil fertility and preventing heavy metals, we recommend compost of Chinese herbal residues as the best organic fertilizer for blueberry, because it not only maximized the soil fertility, but also reduced the heavy-metal pollution risks in the soil. The recommended application amount is 450 g·m 2 ·a − 1 . Though the nutrients supply capacity of edible-fungal-substrates compost was not as good as Chinese-herbal-residues compost, it could be also used as an alternative compost for its superiority in improving the security of blueberry fruit from heavy metals. The recommended application amount is 832 g·m 2 ·a − 1 . The research also provided a valuable method for assessment of soil fertility and soil amelioration in blueberry garden, which could be practical for industrial regions. Further research should pay more attention to the amount and combination methods of organic composts to the yield and quality of blueberries. Declarations Author Contribution declaration All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by [Hao Tang], [Ying Dai], [Lijuan Tang], [Juan Guo], [Fangke Yuan], [Yuan Jin], [Ke Wen], [Jinlu Li] and [Min Xiao], and financially supported by [Heng Xu]. The first draft of the manuscript was written by [Hao Tang] and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. The datasets generated and analyzed during the current study are available from the corresponding author on reasonable request. Funding Declaration and Acknowledgements This study was financially supported by Sichuan Science and Technology Program (2022YFQ0025, 2018YFC1802605), and the Sichuan Provincial Transfer Payment Project (R22ZYZF0001). The authors also wish to thank Professor Shunwen Dong from Sichuan Academy of Agricultural Sciences for the technical assistance. Author Contribution All authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by [Hao Tang], [Ying Dai], [Lijuan Tang], [Juan Guo], [Fangke Yuan], [Yuan Jin], [Ke Wen], [Jinlu Li] and [Min Xiao], and financially supported by [Heng Xu]. The first draft of the manuscript was written by [Hao Tang] and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. Acknowledgement The authors also wish to thank Professor Shunwen Dong from Sichuan Academy of Agricultural Sciences for the technical assistance. 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Ecol indic 49(Feb.):104-109 Pacheco G, Nogueira CR, Meneguin AB, et al. (2017) Development and characterization of bacterial cellulose produced by cashew tree residues as alternative carbon source. Ind Crop Prod 107(15):13-19 Paredes C, Medina E, Bustamante MA, et al. (2016) Effects of spent mushroom substrates and inorganic fertilizer on the characteristics of a calcareous clayey‐loam soil and lettuce production. Soil Use Manage 32:487–494 Peng D, Wu B, Tan H (2019) Effect of multiple iron-based nanoparticles on availability of lead and iron, and micro-ecology in lead contaminated soil. Chemosphere 228:44-53 Qiu K, Xie Y, Xu D, et al. (2018) Ecosystem functions including soil organic carbon, total nitrogen and available potassium are crucial for vegetation recovery. Sci Rep-UK 8(1):7607 Sharma V, Sharma KN, 2 VS, et al. (2013) Influence of Accompanying Anions on Potassium Retention and Leaching in Potato Growing Alluvial Soils. Pedosphere 23(004):464-471 Shuai CA, Bl A, Yl A, et al. (2019) Spatial and temporal changes of soil properties and soil fertility evaluation in a large grain-production area of subtropical plain, China. Geoderma 357(3):113937 Smagula JM, Fastook I (2008) Lowbush blueberry response to several organic fertilizers. Acta Hortic 810(810):741-746 Stewartd. PC, Cameronk. C, Cornforthi. S (1998) Effects of spent mushroom substrate on soil chemical conditions and plant growth in an intensive horticultural system: a comparison with inorganic fertiliser. Soil Res 36(2):185-198 Tang X, Liu B, al e (2018) Strengthening detoxication impacts of Coprinus comatus on nickel and fluoranthene co-contaminated soil by bacterial inoculation. J Environ Manage 206:633-641 Wu B, Hou S, Peng D, et al. (2018) Response of soil micro-ecology to different levels of cadmium in alkaline soil. Ecotox Environ Safe 166:116-122 Wu P, Guo Z, Hua K, et al. (2023) Long-term application of organic amendments changes heavy metals accumulation in wheat grains by affecting soil chemical properties and wheat yields. J Soil Sediment 23(5):2136-2147 Wu S, Zhang C, Li M, et al. (2021) Effects of potassium on fruit soluble sugar and citrate accumulations in Cara Cara navel orange ( Citrus sinensis L. Osbeck). Sci Hortic 283(8):110057 Xie LW, Zhong J, Chen FF, et al. (2015) Evaluation of soil fertility in the succession of karst rocky desertification using principal component analysis. Solid Earth 6(2):515-524 Yang Z, Lu W, Long Y, et al. (2011) Assessment of heavy metals contamination in urban topsoil from Changchun City, China. J Geochem Explor 108(1):27-38 Zhang H, Ke S, Xia M, et al. (2021) Effects of phosphorous precursors and speciation on reducing bioavailability of heavy metal in paddy soil by engineered biochars. Environ Pollut 285:117459 Zhang H, Liu W, Xiong Y, et al. (2024) Effects of dissolved organic matter on distribution characteristics of heavy metals and their interactions with microorganisms in soil under long-term exogenous effects. Sci Total Environ 947(000):11 Additional Declarations No competing interests reported. Supplementary Files SupplementaryMaterials.doc GraphicalAbstract.doc Cite Share Download PDF Status: Published Journal Publication published 09 Jan, 2026 Read the published version in Environmental Geochemistry and Health → Version 1 posted Editorial decision: Revision requested 10 Jul, 2025 Editor assigned by journal 10 Jul, 2025 Submission checks completed at journal 09 Jul, 2025 First submitted to journal 06 Jul, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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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-7058481","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":483483349,"identity":"ba30abc8-a26e-4cca-a47b-e44c99cbd899","order_by":0,"name":"Hao Tang","email":"","orcid":"","institution":"Ecological Protection and Development Research Institute of Aba Tibetan and Qiang Autonomous Prefecture","correspondingAuthor":false,"prefix":"","firstName":"Hao","middleName":"","lastName":"Tang","suffix":""},{"id":483483350,"identity":"f559a6c3-b3df-4977-bb18-f314826999e1","order_by":1,"name":"Ying 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cm.\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7058481/v1/89e57125839b4d9d6bbb6f55.jpg"},{"id":89317041,"identity":"623b1776-469a-4c31-9d28-f543cf0dfb51","added_by":"auto","created_at":"2025-08-18 17:15:41","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":34350,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eThe variation of the integrated soil fertility with fertilization in the study area\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7058481/v1/8581c8957accf99546cf54eb.jpg"},{"id":89317961,"identity":"c9659102-d49c-4e19-bce5-84314ddc3bb3","added_by":"auto","created_at":"2025-08-18 17:31:41","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":30845,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eVariation of nutrients availability with fertilization in blueberry soil\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7058481/v1/2b6b8da58d8ad85812d8d328.jpg"},{"id":89317048,"identity":"007535ad-f290-455c-a0ed-7fef2fc3a9a8","added_by":"auto","created_at":"2025-08-18 17:15:42","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":26393,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eThe risk coefficients of HMs in blueberry soil\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7058481/v1/a0ef67dfac14b87b372857f1.jpg"},{"id":89317591,"identity":"292ec74f-b95b-41af-8015-ae018fe79dc2","added_by":"auto","created_at":"2025-08-18 17:23:41","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":36598,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eThe variation of HMs risk coefficients with fertilization treatments\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7058481/v1/9cbaae830979daf7cab7fd76.jpg"},{"id":89317042,"identity":"7f0d2096-29a1-45b7-add8-b3cbef45cc48","added_by":"auto","created_at":"2025-08-18 17:15:41","extension":"jpg","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":57247,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eFractions of Cd with fertilization in the trial field\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"6.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7058481/v1/9c12a0422a81eb48865d67c4.jpg"},{"id":89317595,"identity":"f35bd690-0a37-40a6-8d30-3a625d8f6e64","added_by":"auto","created_at":"2025-08-18 17:23:42","extension":"jpg","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":30682,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eCd concentrations in blueberry fruit with fertilization treatments\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"7.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7058481/v1/1b0284df02d77379b3ab3b38.jpg"},{"id":89317039,"identity":"799ba95a-69d9-4418-bd2e-4564f1922cfa","added_by":"auto","created_at":"2025-08-18 17:15:41","extension":"jpg","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":49973,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eCorrelation matrix of ISF, nutrients input and HMs risks\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"8.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7058481/v1/8979266033074b3966b64781.jpg"},{"id":89317044,"identity":"5b57a4d1-3055-47e6-a6ef-6f7bb47409bf","added_by":"auto","created_at":"2025-08-18 17:15:41","extension":"jpg","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":45953,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eThe comprehensive effect of fertilization on soil fertility and HMs pollution\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"9.jpg","url":"https://assets-eu.researchsquare.com/files/rs-7058481/v1/068e256c05c2487e00465ae9.jpg"},{"id":100069257,"identity":"57aa99bb-9ac1-462f-96e1-8373cd569962","added_by":"auto","created_at":"2026-01-12 16:12:06","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1637752,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7058481/v1/fa1bfc57-5038-4a20-8b38-4079d1a07ea5.pdf"},{"id":89317594,"identity":"46f87f37-9a2a-46a3-823f-bc1d33d96081","added_by":"auto","created_at":"2025-08-18 17:23:41","extension":"doc","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":231424,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryMaterials.doc","url":"https://assets-eu.researchsquare.com/files/rs-7058481/v1/3bdd90ec7ce1a4720ad2c343.doc"},{"id":89317962,"identity":"c02957a8-8bd7-41dd-b887-3ea0def5f522","added_by":"auto","created_at":"2025-08-18 17:31:42","extension":"doc","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":410624,"visible":true,"origin":"","legend":"","description":"","filename":"GraphicalAbstract.doc","url":"https://assets-eu.researchsquare.com/files/rs-7058481/v1/50918bff8e14a0adc3a31044.doc"}],"financialInterests":"No competing interests reported.","formattedTitle":"Comparative study on Organic Composts in Blueberry: Insights into Soil Physicochemical Properties and Heavy Metal Control","fulltext":[{"header":"1. Introduction`","content":"\u003cp\u003eIndustry and chemical fertilization aggravate heavy metals (HMs) pollution, which is unfavorable for cash crops, especially for blueberry (El Mujtar et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Belonging to Ericaceae taxonomically, \u003cem\u003eVaccinium\u003c/em\u003e, blueberry is rich in anthocyanin, polyphenols and other nutrients (Correa-Betanzo et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2014\u003c/span\u003e). Study suggested that the global blueberry production was 1,934,400 tons in 2021, increased by 183.31% than 2018, and it has been selected for poverty alleviation in mountainous regions (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://www.fao.org/faostat/en/#data/QC\u003c/span\u003e\u003cspan address=\"http://www.fao.org/faostat/en/#data/QC\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e). However, excessive chemical fertilizers increased bioavailability of soil HMs, accelerated the accumulation in blueberry fruits through competition with nutrient channels, and decreased the quality of blueberry to threat people's health (Wu et al. \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Moreover, for lacking of root hair, blueberry mainly absorbs nutrients through Ericoid Mycorrhizae, but that responses sensitively to chemical fertilizers (Carrillo et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2015\u003c/span\u003e), while keeps an affinity to substantial organic sediments (Smagula et al. 2008). Therefore, it is practicable to substitute chemical fertilizers with organic sediments in sustainable production of blueberry.\u003c/p\u003e\u003cp\u003eWith an annual output of millions of tons, the edible fungal substrate (EFS) and Chinese herbal residue (CHR) are two typical secondary biomass wastes (Chen et al. \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Not been fully recycled, those waste materials have caused a series of environmental problems and needed for an urgent disposal in China (Holroyd et al. 2012). Organic composting is regarded as a good method to solve it (Bertoldi et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). As reported, Composts of edible fungal substrate (CEFS) and Chinese herbal residue (CCHR) are all rich in organic acids, nitrogen, potassium and other beneficial nutrients for plants (Leopold et al. \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). And CEFS could counteract the pH-depressing effect induced by chemical fertilizer (Stewartd. et al. 1998). Moreover, the CCHR of \u003cem\u003eIsatis tinctoria\u003c/em\u003e significantly reduced the bioavailability of Cu and Cd by fixation adsorption and precipitation formation (Ma et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Thus, it is feasible and environmental-friendly to apply them in crop fertilization. The two composts were proved on many crops like watermelon, grape and so on, both biomass and fruit quality were improved effectively (Feldman et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2000\u003c/span\u003e; Mugnai et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). But there are few studies focused on the application in blueberry, and neither know the fertilization effects in contrast with conventional fertilizers. Hence, we conducted a field trial to compare the fertilization effects of CEFS and CCHR with conventional fertilizers in blueberry.\u003c/p\u003e\u003cp\u003eThe objectives of this work were (ⅰ) to compare different fertilizations on the integrated soil fertility (ISF) and the nutrients availability; (ⅱ) to reveal different fertilizations on the heavy metal risks in the blueberry soil; (ⅲ) to assessment the bioavailability of Cadmium (Cd) in soil and its concentrations in blueberry fruit with different fertilizations; (iv) to clarify the relationships between nutrients input and heavy metal risks for the blueberry. The findings of this work would provide helpful information for fertilizing in soil properties and blueberry growth, and offer scientific references to the sustainable and safety production of blueberry.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\n \u003ch2\u003e2.1 Material Preparation\u003c/h2\u003e\n \u003cp\u003eCEFS and CCHR were prepared by hyperthermal composting and fermentation according to the methods of Meng (Meng et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e). Firstly, crushed the raw materials (Table \u003cspan class=\"InternalRef\"\u003eS1\u003c/span\u003e) to a particle size of 40 mm, then accumulated the particles into small trapezoidal hills (top length 3 m, bottom length 5 m, height 2.5 m, width 1.5 m) in a composting greenhouse. Secondly, kept the temperature above 50 ℃ for 70 days, then cooled naturally and fermented for 48 days. Finally, further removed impurities and undecomposed organic matter, the refined compost after treatment had a water content of about 30% and a carbon nitrogen ratio of 15\u0026ndash;20. The content of HMs meets the national standards (GB/T 23349\u0026thinsp;\u0026minus;\u0026thinsp;2009). The conventional fertilizers were purchased in the comprehensive market, including the special microbial fruit organic fertilizer popularly used (SFOF) and the potassium sulfate compound fertilizers (PSCF).\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\n \u003ch2\u003e2.2 Experimental Design\u003c/h2\u003e\n \u003cp\u003eThe trial was conducted in a blueberry garden of Sichuan Agricultural Science Academy in Qingbaijiang, Chengdu (30\u0026ordm;52\u0026acute;01\u0026quot;N, 104\u0026ordm;18\u0026acute;47\u0026quot;E). The local climate belongs to the Subtropical monsoon humid climate with an annual temperature of 14.9\u0026ndash;16.7 ℃. The background soil characteristics are listed in Table \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e. A randomized complete block was designed for 8 fertilization treatments, each of which contained 3 fertilization plots, and per plot contained 3 rows of \u0026quot;Gardenblue\u0026quot; (\u003cem\u003eVaccinium ashei\u003c/em\u003e Reade) (Fig. \u003cspan class=\"InternalRef\"\u003e1\u003c/span\u003e). An equal-nitrogen fertilization method of an annual nitrogen rate at 18 g\u0026middot;m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u0026middot;a\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e was implemented referring to Mohsan (Mohsan Zafar et al. 2007). The experiment was repeated thrice respectively in 2022 to 2024, for details referring to Table\u0026nbsp;\u003cspan class=\"InternalRef\"\u003e2\u003c/span\u003e.\u003c/p\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003ctable id=\"Tab1\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eBackground properties of fertility and HMs in the blueberry soil Units: mg\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eproperties\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003evalues\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eproperties\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003evalues\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eproperties\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003evalues\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003epH\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e6.4\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eSOM\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e37100\u0026thinsp;\u0026plusmn;\u0026thinsp;1500\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eA-Cr\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e15\u0026thinsp;\u0026plusmn;\u0026thinsp;2.5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eTN\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1610\u0026thinsp;\u0026plusmn;\u0026thinsp;310\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eCEC\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e13.7\u0026thinsp;\u0026plusmn;\u0026thinsp;1.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eCd\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.49\u0026thinsp;\u0026plusmn;\u0026thinsp;0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eTP\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e1092\u0026thinsp;\u0026plusmn;\u0026thinsp;120\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eCu\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e39.7\u0026thinsp;\u0026plusmn;\u0026thinsp;3.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eA-Cd\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.17\u0026thinsp;\u0026plusmn;\u0026thinsp;0.03\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eTK\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e15000\u0026thinsp;\u0026plusmn;\u0026thinsp;984\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eA-Cu\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e5.3\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eS-Cu\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e150\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAN\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e165\u0026thinsp;\u0026plusmn;\u0026thinsp;21\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eNi\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e31.7\u0026thinsp;\u0026plusmn;\u0026thinsp;2.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eS-Ni\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e70\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAP\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e51.1\u0026thinsp;\u0026plusmn;\u0026thinsp;8.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eA-Ni\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e4.1\u0026thinsp;\u0026plusmn;\u0026thinsp;0.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eS-Cr, I-Cr\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e150, 850\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eAK\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e86\u0026thinsp;\u0026plusmn;\u0026thinsp;13\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eCr\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e80.8\u0026thinsp;\u0026plusmn;\u0026thinsp;7.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eS-Cd, I-Cd\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0.3, 2\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\" colspan=\"6\"\u003e\n \u003cp\u003eNote: A refers to available fraction of elements; S and I refer to screening and intervention standard of HMs.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n \u003cdiv class=\"gridtable\"\u003e\n \u003cdiv align=\"left\" class=\"colspec\"\u003e\u003cbr\u003e\u003c/div\u003e\n \u003ctable id=\"Tab2\" border=\"1\"\u003e\n \u003ccaption language=\"En\"\u003e\n \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\n \u003cdiv class=\"CaptionContent\"\u003e\n \u003cp\u003eDifferent fertilization treatments and dosages for each growth period\u003c/p\u003e\n \u003c/div\u003e\n \u003c/caption\u003e\n \u003cthead\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" rowspan=\"3\"\u003e\n \u003cp\u003eTreatments\u003c/p\u003e\n \u003cp\u003e(equivalent N of 18 g\u0026middot;m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e\u0026middot;a\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eFertilization patterns\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003ePrimary fertilization (g\u0026middot;m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eFlorescence fertilization (g\u0026middot;m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eFruit bearing fertilization(g\u0026middot;m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eFruit swelling\u003c/p\u003e\n \u003cp\u003efertilization(g\u0026middot;m\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e)\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\" rowspan=\"2\"\u003e\n \u003cp\u003eFertilization time\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eNov. 20, 2021\u003c/p\u003e\n \u003cp\u003eNov. 25, 2022\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eJan. 22, 2022\u003c/p\u003e\n \u003cp\u003eJan.26 2023\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMar. 17, 2022\u003c/p\u003e\n \u003cp\u003eMar. 15, 2023\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMay 21, 2022\u003c/p\u003e\n \u003cp\u003eMay 27, 2023\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eNov.18, 2023\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eJan.22 2024\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMar. 20, 2024\u003c/p\u003e\n \u003c/th\u003e\n \u003cth align=\"left\"\u003e\n \u003cp\u003eMay 30, 2024\u003c/p\u003e\n \u003c/th\u003e\n \u003c/tr\u003e\n \u003c/thead\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eCK\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eNF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e0\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eT1\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCEFS\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e416\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e208\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e104\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e104\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eT2\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCEFS\u0026thinsp;+\u0026thinsp;PSCF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e208\u0026thinsp;+\u0026thinsp;45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e104\u0026thinsp;+\u0026thinsp;22.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e52\u0026thinsp;+\u0026thinsp;11.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e52\u0026thinsp;+\u0026thinsp;11.25\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eT3\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCCHR\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e225\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e112.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e56.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e56.25\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eT4\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eCCHR\u0026thinsp;+\u0026thinsp;PSCF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e112.5\u0026thinsp;+\u0026thinsp;45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e56.25\u0026thinsp;+\u0026thinsp;22.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e28.13\u0026thinsp;+\u0026thinsp;11.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e28.13\u0026thinsp;+\u0026thinsp;11.25\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eT5\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSFOF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e128\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e32\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e32\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eT6\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003eSFOF\u0026thinsp;+\u0026thinsp;PSCF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e64\u0026thinsp;+\u0026thinsp;45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e32\u0026thinsp;+\u0026thinsp;22.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e16\u0026thinsp;+\u0026thinsp;11.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e16\u0026thinsp;+\u0026thinsp;11.25\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e\u003cstrong\u003eT7\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003ePSCF\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e45\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e22.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd align=\"left\"\u003e\n \u003cp\u003e22.5\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n \u003ctfoot\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"6\"\u003eNote: NF: not fertilized; CEFS: organic composts of edible fungal substrates; PSCF: potassium sulfate compound fertilizers; CCHR: organic composts of Chinese herbal residues; SFOF: special organic fertilizer fruit in market; PSCF: potassium sulfate compound fertilizers.\u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tfoot\u003e\n \u003c/table\u003e\n \u003c/div\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\n \u003ch2\u003e2.3 Sampling and Analysis\u003c/h2\u003e\n \u003cp\u003eFresh soil samples in 0\u0026ndash;20 cm rhizosphere of each plot were collected by five point sampling method according to Xie (Xie et al. \u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e). After naturally air dried and homogenized, the soils were sieved through 2-mm mesh in the laboratory to determine the physicochemical properties. Soil pH was measured by pH meter (SevenCompact-s210) in a soil suspension (ratio of soil: water (w/v) was 1: 2.5). The total nitrogen (TN), phosphorus (TP), potassium (TK) were respectively determined by Kjeldahl method (Nozawa et al. \u003cspan class=\"CitationRef\"\u003e2005\u003c/span\u003e), sodium hydroxide alkali melting molybdenum antimony anti-colorimetry (Gonzalez et al. \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e), and acid melting flame photometry (Burr \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e). The alkali hydrolyzed nitrogen (AN), quick available phosphorus (AP), and effective potassium (AK) were tested by the alkali dissolving diffusion method (Shuai et al. \u003cspan class=\"CitationRef\"\u003e2019\u003c/span\u003e), 0.5 mol\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e sodium bicarbonate extraction method (Liu et al. \u003cspan class=\"CitationRef\"\u003e2011\u003c/span\u003e), and 1 mol\u0026middot;L\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e ammonium acetate extraction flame photometry (Qiu et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e), respectively. In addition, the Potassium dichromate heating method was used for soil organic matter (SOM) determination (Gerenfes et al. \u003cspan class=\"CitationRef\"\u003e2022\u003c/span\u003e), while the sodium acetate sodium chloride exchange method for cation exchange capacity (CEC) measurement (Millar et al. \u003cspan class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e\n \u003cp\u003eThe concentrations of Cu, Ni, Cr, Cd were determined by atomic absorption spectroscopy while their availability were evaluated by the toxicity characteristic leaching procedure (TCLP) (Moon et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e). The fractions of HMs containing HOAc-extractable, reducible, oxidizable, residual were analyzed by BCR sequential extraction method (Wu et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e). The degree of soil contamination risk was divided by the national standard of China (GB15618-2018), in which the screening and intervention thresholds are applied for evaluating the threats to the quality and safety of agricultural products, growth of crops, and soil ecological environment(Chen et al. \u003cspan class=\"CitationRef\"\u003e2021\u003c/span\u003e). The pollution risks were evaluated by the Nemerow comprehensive pollution index (NPI) as Table S2 (Moghtaderi et al. \u003cspan class=\"CitationRef\"\u003e2018\u003c/span\u003e), and the classification criterions for NPI was executed as Table S3 .\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\n \u003ch2\u003e2.4 Data Analysis and Graphing\u003c/h2\u003e\n \u003cp\u003eThe mean values and standard deviations of all data originating from three replicates in this study were calculated. Considering the numerous and complicated factors on soil nutrient, integrated soil fertility (ISF) is often introduced to evaluate soil quality (Getachew et al. 2017). The evaluation of ISF was based on the factor score analysis model according to the Principal Component Analysis (PCA) via SPSS (Xie et al. \u003cspan class=\"CitationRef\"\u003e2015\u003c/span\u003e). The calculation formulae were designed in Table S4. Table S5 to S7 presented the computation process of integrated soil fertility (ISF), in which data standardizastion, dimension reduction analysis, determination of principal component coefficients and ISF equation construction included. Statistical significance was determined by one-way ANOVA in SPSS18.0 software using least significant difference (LSD) method to compare the mean values of each sample at a significant level of p\u0026thinsp;\u0026lt;\u0026thinsp;0.05. All values were described using Origin 9.1 software in this paper.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\u003ch2\u003e3.1 Changes of Integrated Soil Fertility and Nutrients Availability in the soil\u003c/h2\u003e\u003cp\u003eThe integrated soil fertility (ISF) with fertilization is showed in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e. The ISF in T2 (CEFS\u0026thinsp;+\u0026thinsp;PSCF) and T3 (CCHR) increased by 149.31% and 139.71% than CK significantly, manifesting the highest fertility. When applied the three organic fertilizers individually, the ISF was T3(CCHR)\u0026thinsp;\u0026gt;\u0026thinsp;T5 (SFOF)\u0026thinsp;\u0026gt;\u0026thinsp;T1(CEFS), while the combination efficiency with PSCF was T2 (CEFS\u0026thinsp;+\u0026thinsp;PSCF)\u0026thinsp;\u0026gt;\u0026thinsp;T4(CCHR\u0026thinsp;+\u0026thinsp;PSCF)\u0026thinsp;\u0026gt;\u0026thinsp;T6 (SFOF\u0026thinsp;+\u0026thinsp;PSCF). Fertilization effects on nutrients availability was showed in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e. The available nitrogen (AN) in T1 increased by 5.94% than CK, while the other treatments were all decreased. And the available phosphorus (AP) in T2, T4, T6 were increased, with the others decreased comparing to CK. And the availability of potassium (AK) in all fertilized treatments was improved by 39.40%-140.91% than CK.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e3.2 Assessment of Heavy Metal Risks in the Soil\u003c/h2\u003e\u003cp\u003eThe heavy metals (HMs) pollution degree of the garden before fertilization was manifested in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e, that based on the screening and intervention standards from the Ministry of Ecology and Environment, P. R. China (GB15618-2018). Results showed that the screening risks of Cu, Ni, Cr were 26.51%, 45.3%, 53.88%, respectively. But the screening risk coefficient of Cd was up to 163.33%, while its intervention risk was 24.5%. Error bars manifested the change amplitude of different HMs pollution indexes, which indicated that the changing range of the four HMs was Cd\u0026thinsp;\u0026gt;\u0026thinsp;Cr\u0026thinsp;\u0026gt;\u0026thinsp;Ni\u0026thinsp;\u0026gt;\u0026thinsp;Cu.\u003c/p\u003e\u003cp\u003eThe HMs concentrations and the corresponding Nemerow integrated contamination index (NPI) with fertilization were listed in table S8 and S9. The background NPI before fertilization was 1.26. According to Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, the NPI in CK (not fertilization) was 1.45 (slight pollution level), and that in T3 (CCHR) decreased by 32.41%, significantly. Though there were no significant differences among T1 (NPI\u0026thinsp;=\u0026thinsp;1.22), T2 (NPI\u0026thinsp;=\u0026thinsp;1.5), T4 (NPI\u0026thinsp;=\u0026thinsp;1.35), T5 (NPI\u0026thinsp;=\u0026thinsp;1.59), but T1 was still preferable in reducing the risks. However, an apparent risk elevation was recorded in T6 (NPI\u0026thinsp;=\u0026thinsp;1.85) and T7 (NPI\u0026thinsp;=\u0026thinsp;2.16), whereas T7 was regarded as a moderate pollution (2\u0026thinsp;\u0026lt;\u0026thinsp;NPI\u0026thinsp;\u0026le;\u0026thinsp;3) notably.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e3.3 Bioavailability of Cd in the Soil and its Concentrations in the Fruit\u003c/h2\u003e\u003cp\u003eWe compared the fractions of Cd in the soil and its concentrations in the fruit to assessment the bioavailability of Cd with fertilization (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e). Compared with CK, T1, T3 decreased HOAc-extractable Cd by 39.37% and 23.94%, whereas T5 and T7 increased it by 23.30% and 23.41%. All treatments with organic composts (T1-T4) cut down the HOAc-extractable Cd by 9.87\u0026ndash;44.45%, and T1, T2 further reduced the reducible Cd by 11.07, 33.51%. The organic composts (particularly in T2, T3) were also advantageous to the increase of residual Cd. Figure\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e showed that the concentrations of Cd in all treatments were less than 0.05 mg\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e (the national food safety standards). Compared with CK (not fertilization), Cd concentrations of blueberry fruit in T1(CEFS), T3 (CCHR) were reduced significantly at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 level. At the same time, that in T6 (SFOF\u0026thinsp;+\u0026thinsp;PSCF), T7 (PSCF) were increased significantly (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05), and the rest treatments showed no significant differences.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e3.4 Relationships between Nutrients Input and HMs Risks\u003c/h2\u003e\u003cp\u003eCorrelation matrix in Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e8\u003c/span\u003e illustrated the relationships between the nutrients input and the HMs risks. The soil fertility is positively relevant to principal nutrients with a relevance of N\u0026thinsp;\u0026gt;\u0026thinsp;P\u0026thinsp;\u0026gt;\u0026thinsp;SOM\u0026thinsp;\u0026gt;\u0026thinsp;K, where N input was significantly correlated at 0.05 level. The correlation coefficient between the input of P and N was 0.761, and 0.726 between the input of P and K (p\u0026thinsp;\u0026lt;\u0026thinsp;0.05). The SOM input was positively related to the ISF, and the input of N and P, while adverse impact on K. The ISF was negatively related to all HMs, especially to Cu (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01), but was relatively lower relevant to Cd. Risks of the four HMs was all negatively correlated with the SOM input. According to the RDA analysis in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e, the distribution of T1, T2, T3, T4 were consistent with the main soil elements (TN, TP, AK, AN, AK and SOM). And the distribution of CK, T5, T6, T7 were deviated from the main nutrient elements. But for the pollutants in the soil (Cu, Ni, Cr, Cd), the distribution trends were opposite.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\u003ch2\u003e4.1 Fertilization Effects on Integrated Soil Fertility and Nutrients Availability for blueberry\u003c/h2\u003e\u003cp\u003eTrial results indicated that T2 (Composts of edible fungal substrate\u0026thinsp;+\u0026thinsp;the potassium sulfate compound fertilizers, CEFS\u0026thinsp;+\u0026thinsp;PSCF) and T3 (Composts of Chinese herbal residue, CCHR) manifest the highest fertility, mainly because the fungal residues in the organic compounds increased the content of microbial biomass, supplied more dissolved organic carbon (C) and nitrogen (N) for the soil (Paredes et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). When applied the three organic fertilizers individually, the integrated soil fertility (ISF) was T3(CCHR)\u0026thinsp;\u0026gt;\u0026thinsp;T5 (the special microbial fruit organic fertilizer popularly used, SFOF)\u0026thinsp;\u0026gt;\u0026thinsp;T1(CEFS), which meant CCHR was better for fertility improvement. The combination efficiency with PSCF was T2 (CEFS\u0026thinsp;+\u0026thinsp;PSCF)\u0026thinsp;\u0026gt;\u0026thinsp;T4(CCHR\u0026thinsp;+\u0026thinsp;PSCF)\u0026thinsp;\u0026gt;\u0026thinsp;T6 (SFOF\u0026thinsp;+\u0026thinsp;PSCF), which meant CEFS and CCHR were better for fertility retention. It means that the combining fertility of the conventional and chemical fertilizers was not as good as the combination of organic and chemical fertilizers. Previous studies also mentioned that the combination of Chinese herbal residue and potassium sulfate compound (T4) could increase the activity of urease and phosphatase (P) to accelerate the decomposition of urea and insoluble phosphorus in soil (Chang et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2014\u003c/span\u003e), thereby improving the ISF. But in T6, the application of PSCF weakened the ISF, mainly because chemical fertilizer disturbed the soil microflora in the microbial organic fertilize (SFOF), and restricted the microbial metabolic activity, which correspondingly decelerated the decomposition and circulation of nutrients in the soil (Gu et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Therefore, it is feasible to apply CEFS and CCHR to replace conventional fertilizers for a better nutrient supply in blueberry cultivation.\u003c/p\u003e\u003cp\u003eIn all treatments, T1 could elevate the Available Nitrogen (AN), which mainly because that the fungal residue provided more carbon sources for microorganism to accelerate the secretory of extracellular depolymerase, thus benefited the mineralization of organic nitrogen (Pacheco et al. \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). But when combined with inorganic fertilizer, more urea in PSCF decreased the C/N ratio of soil, which inhibited cellulose decomposing bacteria and reduced the release of AN in fungal residue (Ostrowska et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). The available phosphorus (AP) in T2, T4, T6 increased than CK, mainly because more organic matters in soil kept more moisture, accelerating the dissolution and migration of mineral phosphorus to root system (Moorberg et al. \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). As for potassium (K), its availability in fertilized treatments was overall improved, because fertilization increased the special adsorption sites (K\u003csub\u003eX\u003c/sub\u003e) to raise the release power of soil K\u003csup\u003e+\u003c/sup\u003e (Sharma et al. \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2013\u003c/span\u003e). But the application of CCHR (T3, T4) was still the best, mainly because of the attachment to potassium ions by the Chinese medicine residues. Research has shown that traditional Chinese medicine residue compost contains the strain DGNK-JJ1, which has strong effect on potassium hydrolysis. This strain is of fibrotic fiber microorganism (\u003cem\u003eCellulose microbium cellulans\u003c/em\u003e), which has nitrogen fixation, produces β -1,3-glucanase, chitinase, and can degrade monocyclic aromatic hydrocarbons and release K\u003csup\u003e+\u003c/sup\u003e (Dou et al. 2019). During the growth period of blueberry, Nitrogen is an important element for the plant growth and leaf development, Phosphorus can promote cell division and enlargement of blueberry fruits, and Potassium is for fruit coloring, anthocyanin synthesis and sugar metabolism (Wu et al. \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Therefore, the application of Composts of edible fungal substrate and Chinese herbal residue can promote nutrient availability and macro-elements supply to soil, thereby increasing the yield and quality of blueberries.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\u003ch2\u003e4.2 Fertilization Effects on heavy metal pollution risks for blueberry\u003c/h2\u003e\u003cp\u003eAs for the heavy metal pollution risks, when the content of soil pollutants is not greater than the screening standard, the pollution risk of farmland can be generally ignored. When it is between the screening and intervention values, there may be pollution risks, collaborative monitoring and safety utilization measures should be adopted. When it is higher than the intervention values, edible crops are prohibited to cultivate as result of high contamination risks in soil (Lu et al. \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). According to our investigation (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e), screening risks of Cu, Ni, Cr were 26.51%, 45.3%, 53.88%, respectively, which meant there was no pollution risk of the three HMs in this blueberry garden. But considering the heavy industry in Qingbaijiang, the potential contamination risks can\u0026rsquo;t still be overlooked. However, the screening risk coefficient of Cd was up to 163.33% while its intervention risk was 24.5%, which meant special attention should be paid to this element, may ascribing to the relatively high background value of Cd in the northeast of Chengdu plain (Deng et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). In addition, error bars on the columns manifested the change amplitude of different HMs pollution indexes, which indicated that the changing range of the four HMs was Cd\u0026thinsp;\u0026gt;\u0026thinsp;Cr\u0026thinsp;\u0026gt;\u0026thinsp;Ni\u0026thinsp;\u0026gt;\u0026thinsp;Cu. It was reported that Cd was most easy to be affected by human activities (Laxmi et al. 2022), so Cd deserved more attention for the safety production in the blueberry garden.\u003c/p\u003e\u003cp\u003eIn terms of the Nemerow comprehensive pollution index (NPI), the background value before fertilization was 1.26, defining as a slight pollution level according to the classification criterions in Table S3 (Yang et al. \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e2011\u003c/span\u003e). According to Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003e, the NPI in CK (not fertilization) was 1.45 (slight pollution level), which was higher than the background value before fertilization. It showed that there exist exogenous HMs input to the garden. As located in an industrial zone, careless management could accumulated much more HMs because of various human activities such as fossil fuel combustion, automotive exhaust emission, refuse burning and wastewater irrigation (Tang et al. 2018). The contamination risk in T3 (NPI\u0026thinsp;=\u0026thinsp;0.98) was significantly abated by 32.41% compared to CK, which achieved to the non-pollution level (0\u0026thinsp;\u0026lt;\u0026thinsp;\u003cem\u003eI\u003c/em\u003e\u0026thinsp;\u0026le;\u0026thinsp;1), indicating CCHR was best in HMs risks reducing. Besides, the NPI of T1 among the other organic treatments (T1-T6) was still lower (NPI\u0026thinsp;=\u0026thinsp;1.22), indicated that CEFS was also relatively better in reducing the risks. It is reported that organic fertilization has passivation effect on HMs by the intrinsic components of fertilizers, and organic matters are favorable to the valence reduction and detoxification of HMs (Alam et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). And organic materials could stimulate the activities of soil enzymes and improving bacterial abundance to relieve stress of HMs (Liu et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Both edible fungal substrate and Chinese herbal residue contain rich organic matter, whose composts (CEFS, CCHR) have good effects in improving microbial activity and inhibiting heavy metal migration for blueberry soil. But high concentrations of HMs in chemical fertilizers could restrain the growth of soil microorganism like bacteria, fungi and actinomycetes (Zhang et al. \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). That\u0026rsquo;s why an obvious elevation of the risks was recorded in T6 and T7. Therefore, composts of edible fungal substrate and Chinese herbal residue could reduce the comprehensive pollution risks of heavy metals in blueberry planting.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec15\" class=\"Section2\"\u003e\u003ch2\u003e4.3 Fertilization Effects on Bioavailability of soil Cd and Fruit safety of blueberry\u003c/h2\u003e\u003cp\u003eGiven the intervention risk of Cd in the soil was 24.5%, special attention should be paid to this element, we analyzed bioavailability of the soil Cd and safety of the blueberry fruit. Residual and oxidizable forms of HMs are thought as relative stable while reducible and HOAc-extractable forms as instable (Peng et al. \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). Compared with CK, T1, T3 decreased HOAc-extractable Cd by 39.37% and 23.94%, whereas T5 and T7 increased it somewhat (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003e). Meanwhile, all treatments with organic composts (T1-T4) cut down the HOAc-extractable Cd by 9.87\u0026ndash;44.45%, and T1, T2 further reduced the reducible Cd by 11.07, 33.51%. Therefore, CEFS (T1) and CCHR (T3) manifested the best immobilization effect on Cd, mainly because the intercellular deposition of passivation bacteria and the complexation of SOMs (Fang et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). The combination of PSCF improved the HOAc-extractable Cd, mainly due to the chemical fertilizer could lead to a higher Cd accumulation in plants (Liu et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eFurthermore, compared with CK (not fertilization), Cd concentrations of blueberry fruit in T1(CEFS), T3 (CCHR) were reduced significantly at p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 level (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003e), while that in T6 (SFOF\u0026thinsp;+\u0026thinsp;PSCF), T7 (PSCF) were significantly increased, and the rest treatments showed no significant differences. Though the concentrations of Cd in all treatments were not exceeding the limitation of fresh fruit (Cd\u0026thinsp;\u0026lt;\u0026thinsp;0.05mg\u0026middot;kg\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e) according to the national food safety standards in China (GB 2762\u0026thinsp;\u0026minus;\u0026thinsp;2017), the organic fertilizers could further reduce the accumulation of HMs in fruits. This was in similarity with the concentration of available Cd in soil, owing to the passivation effect to Cd by CEFS and CCHR. That is, composts of edible fungal substrate and Chinese herbal residue can reduce the available state of soil Cd to lower the Cd content in the plant, thereby ensuring the safety of blueberry fruits. Therefore, it is necessary to substitute composts of edible fungal substrate and Chinese herbal residue for chemical fertilizers in safety production of blueberry.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec16\" class=\"Section2\"\u003e\u003ch2\u003e4.4 Comprehensive Effects of Fertilization on Blueberry\u003c/h2\u003e\u003cp\u003eAccording to the correlation analysis, we found the integrated soil fertility (ISF) of blueberry was mostly affected by the input of N. In growth periods of blueberry, N is the most important element in blueberry leaves for synthesis of soluble sugar, anthocyanin, flavonoids, total phenols and adjusting the fruit width and yield (Bryla et al. \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). Similarly, we found the input of P was significantly interrelated with N input, while P input significantly affected the amount of K as well. Usually throughout the entire growth period of blueberry, the requirements ratio of N, P, K is 4:1:2, \u0026lsquo;N determines P, K\u0026rsquo;is widely recognized as a fundamental principle of blueberry fertilization (Emmanuel et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). That\u0026rsquo;s why we adopted an equal-nitrogen fertilization method to compare different fertilization effects in this article.\u003c/p\u003e\u003cp\u003eIn addition, SOM input was also positive related to ISF, which is in similarity with previous study that SOM was regarded as the ultimate determinant of soil fertility for adjusting soil bulk density, water holdup, aggregation, root penetration and compaction (Chalise et al. \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). As far as the relationships between principal nutrients, the input of SOM had a positive effect on the input of N and P while adverse impact on K, which are in line with previous studies (Lewis et al. \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e1991\u003c/span\u003e). But because potassium was majorly supplied by chemical fertilizer (PSCF), that\u0026rsquo;s why CEFS\u0026thinsp;+\u0026thinsp;PSCF, CCHR\u0026thinsp;+\u0026thinsp;PSCF obtained the relative higher ISF scores in our experiment. Regarding up to 90% of soil N is held in SOM in an organic form (Nguyen et al. 2011), by which positively and negatively affected the adsorption intensity of P and K respectively (Hongwen Sun et al. 2008). So, when we apply organic fertilizers to blueberry, we need to supplement potassium fertilizer in time. We can consider replacing nitrogen and phosphorus fertilizers by organic composts while combining exogenous potassium fertilizer in blueberry cultivation.\u003c/p\u003e\u003cp\u003eOn the other hand, the ISF was negatively related to all HMs, might be attributed to HMs reducing nutrients maintenance, such as decelerating N mineralization by inhibition of microbial activity (Babich et al. 1985), or reducing P, K adsorption by occupying part of the adsorption sites in soil colloids (Zhang et al. \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). The ISF was negatively related to Cu (p\u0026thinsp;\u0026lt;\u0026thinsp;0.01), but was relatively lower relevant to Cd, mainly because of the lower resolution rate and lower mobility of Cu\u003csup\u003e2+\u003c/sup\u003e in soil than Cd\u003csup\u003e2+\u003c/sup\u003e (Cavallaro et al. 1980), thus much more Cu\u003csup\u003e2+\u003c/sup\u003e would remain in the soil rather than flowing with the root absorption and microbial driving. As a result, the immobilization of Cd in soil-plant system deserved more attention. In addition, SOM input was also negatively correlated with the risks of the four HMs, mainly because the chelation of organic matters reducing bioavailability of HMs (Boominathan et al. 2003), which may provide theoretical basis for usage of organic composts in blueberry garden to reduce HMs pollution risks.\u003c/p\u003e\u003cp\u003eAccording to the RDA analysis in Fig.\u0026nbsp;\u003cspan refid=\"Fig9\" class=\"InternalRef\"\u003e9\u003c/span\u003e, the treatments of T1, T2, T3, T4 obtained more effective N, P, K and SOM, while suffering less HMs pollution from Cu, Ni, Cd, Cr. On the one hand, organic composts can increase soil humus content, improve soil aggregate structure, and enhance soil water and fertilizer retention capacity. On the other hand, organic composts can provide more carbon sources to stimulate microbial activity and promote the transformation of heavy metal forms, and reduce the bioavailability of soil HMs. That is, the organic-fertilization treatments of CEFS and CCHR could bring superior comprehensive fertilization efficiency and less pollution for blueberry. However, non-fertilization or the application of inorganic fertilizers (SFOF and PSCF) may have an adverse effect.\u003c/p\u003e\u003c/div\u003e"},{"header":"5. Conclusions","content":"\u003cp\u003eThis study revealed that there were some nutrients deficiency and heavy metals (HMs) pollution risks for blueberry in the northeast plain of Chengdu. According to our study, we found the integrated soil fertility of blueberry was mostly affected by the input of nitrogenous and organic matters. Composts of edible fungal substrates and Chinese herbal residue were beneficial to increase soil organic matter content and promote nitrogen mineralization, thereby improving the soil fertility and nutrient supply for blueberry. But we found excess organic matters in blueberry soil would affect the release of potassium ions, it is necessary to replenish potassium fertilizer in time for blueberry. In addition, we found the integrated soil fertility was suppressed by heavy metals in the soil, especially cadmium, which reducing nutrients maintenance by decelerating Nitrogen-mineralizing microorganisms and occupying the adsorption sites of P, K in the soil colloids. But composts of edible fungal substrates and Chinese herbal residues could provide sufficient organic matter for the soil, and reduce the bioavailability of heavy metals through chelation, which effectively safeguarded the security of blueberry fruit. In a word, comparing to the Special Microbial Fruit Organic Fertilizer commonly used in the market and Potassium Sulfate Compound Fertilizer, compost of edible fungal substrates and Chinese herbal residues demonstrated a better fertility and heavy-metal prevention efficiency.\u003c/p\u003e\u003cp\u003eFurthermore, in terms of the comprehensive effect of improving soil fertility and preventing heavy metals, we recommend compost of Chinese herbal residues as the best organic fertilizer for blueberry, because it not only maximized the soil fertility, but also reduced the heavy-metal pollution risks in the soil. The recommended application amount is 450 g\u0026middot;m\u003csup\u003e2\u003c/sup\u003e\u0026middot;a\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. Though the nutrients supply capacity of edible-fungal-substrates compost was not as good as Chinese-herbal-residues compost, it could be also used as an alternative compost for its superiority in improving the security of blueberry fruit from heavy metals. The recommended application amount is 832 g\u0026middot;m\u003csup\u003e2\u003c/sup\u003e\u0026middot;a\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The research also provided a valuable method for assessment of soil fertility and soil amelioration in blueberry garden, which could be practical for industrial regions. Further research should pay more attention to the amount and combination methods of organic composts to the yield and quality of blueberries.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAuthor Contribution declaration\u003c/h2\u003e\n\u003cp\u003eAll authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by [Hao Tang], [Ying Dai], [Lijuan Tang], [Juan Guo], [Fangke Yuan], [Yuan Jin], [Ke Wen], [Jinlu Li] and [Min Xiao], and financially supported by [Heng Xu]. The first draft of the manuscript was written by [Hao Tang] and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript. The datasets generated and analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003ch2\u003eFunding\u003c/h2\u003e\n\u003cp\u003eDeclaration and Acknowledgements\u003c/p\u003e\n\u003cp\u003eThis study was financially supported by Sichuan Science and Technology Program (2022YFQ0025, 2018YFC1802605), and the Sichuan Provincial Transfer Payment Project (R22ZYZF0001). The authors also wish to thank Professor Shunwen Dong from Sichuan Academy of Agricultural Sciences for the technical assistance.\u003c/p\u003e\n\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\n\u003cp\u003eAll authors contributed to the study conception and design. Material preparation, data collection and analysis were performed by [Hao Tang], [Ying Dai], [Lijuan Tang], [Juan Guo], [Fangke Yuan], [Yuan Jin], [Ke Wen], [Jinlu Li] and [Min Xiao], and financially supported by [Heng Xu]. The first draft of the manuscript was written by [Hao Tang] and all authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003ch2\u003eAcknowledgement\u003c/h2\u003e\n\u003cp\u003eThe authors also wish to thank Professor Shunwen Dong from Sichuan Academy of Agricultural Sciences for the technical assistance.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAlam M, Hussain Z, Khan A, et al. 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Sci Total Environ 947(000):11\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"environmental-geochemistry-and-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"egah","sideBox":"Learn more about [Environmental Geochemistry and Health](https://www.springer.com/journal/10653)","snPcode":"10653","submissionUrl":"https://submission.nature.com/new-submission/10653/3","title":"Environmental Geochemistry and Health","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Organic composts, soil fertility, plant performance, heavy metals","lastPublishedDoi":"10.21203/rs.3.rs-7058481/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7058481/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eOrganic fertilization is an essential method for sustainable agricultural development. Composts of edible fungal substrates (CEFS) and Chinese herbal residues (CCHR) are potential ecological organic fertilizers, but rarely used in blueberry cultivation. The purport is to compare different fertilizations on the integrated soil fertility (ISF), nutrients availability, and the heavy metals (HMs) risks in the blueberry soil and fruit; simultaneously to clarify the relationships between nutrients input and HMs risks for the blueberry. In this study, we conducted a field trial using CEFS and CCHR in blueberry, comparing to the special fruit organic fertilizer in the market (SFOF) and potassium sulfate compound fertilizers (PSCF). Results showed that the ISF of blueberry was mostly affected by the input of nitrogenous and organic matters, and restricted by HMs. CEFS and CCHR demonstrated a better fertility and heavy-metal prevention efficiency comparing to SFOF and PSCF. But excess organic matters in soil would affect blueberry's absorption of potassium, it is necessary to replenish potassium fertilizer in time for blueberry. Our results would provide a theoretical basis for the application of CEFS and CCHR in the safety production of blueberry.\u003c/p\u003e","manuscriptTitle":"Comparative study on Organic Composts in Blueberry: Insights into Soil Physicochemical Properties and Heavy Metal Control","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-18 17:15:37","doi":"10.21203/rs.3.rs-7058481/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-07-10T11:36:23+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-07-10T11:35:33+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-07-09T18:02:17+00:00","index":"","fulltext":""},{"type":"submitted","content":"Environmental Geochemistry and Health","date":"2025-07-06T14:34:36+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"environmental-geochemistry-and-health","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"egah","sideBox":"Learn more about [Environmental Geochemistry and Health](https://www.springer.com/journal/10653)","snPcode":"10653","submissionUrl":"https://submission.nature.com/new-submission/10653/3","title":"Environmental Geochemistry and Health","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"e86fa01d-f723-4863-be6e-f312b1878ed6","owner":[],"postedDate":"August 18th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-01-12T16:03:21+00:00","versionOfRecord":{"articleIdentity":"rs-7058481","link":"https://doi.org/10.1007/s10653-026-02984-5","journal":{"identity":"environmental-geochemistry-and-health","isVorOnly":false,"title":"Environmental Geochemistry and Health"},"publishedOn":"2026-01-09 15:58:09","publishedOnDateReadable":"January 9th, 2026"},"versionCreatedAt":"2025-08-18 17:15:37","video":"","vorDoi":"10.1007/s10653-026-02984-5","vorDoiUrl":"https://doi.org/10.1007/s10653-026-02984-5","workflowStages":[]},"version":"v1","identity":"rs-7058481","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7058481","identity":"rs-7058481","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}