Effects of hydrothermal charcoal on saline-alkaline soil properties in the Yellow River Delta

Effects of hydrothermal charcoal on saline-alkaline soil properties in the Yellow River Delta | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 25 February 2025 V1 Latest version Share on Effects of hydrothermal charcoal on saline-alkaline soil properties in the Yellow River Delta Authors : Shuo Yang and Yujun Ma 0009-0007-9689-3921 Authors Info & Affiliations https://doi.org/10.22541/au.174048710.05206800/v1 Published Plant and Soil Version of record Peer review timeline 161 views 120 downloads Contents Abstract Supplementary Material Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract This study focused on the effects of biochar and hydrothermally modified biochar on the physicochemical properties and other aspects of saline-alkaline soil in the Yellow River Delta. In order to improve the saline-alkaline soils in the Yellow River Delta, hydrothermal peanut hull biochar (FBC1), hydrothermal wheat straw biochar (FBC2), hydrothermal corn stover biochar (FBC3), hydrothermal rice hull biochar (FBC4) and phosphoric acid-modified biochar were prepared to remediate the saline-alkaline soils. It was found that the addition of biochar significantly increased soil porosity, water content, cation exchange capacity (CEC), and organic matter content, while soil bulk weight, total water-soluble salts, exchangeable Na + content (EX-Na + ), and exchangeable sodium percentage (ESP) significantly decreased. Modified biochar showed significantly higher effect in reducing total soil water-soluble salts, EX-Na + and ESP compared to unmodified biochar. Unmodified biochar reduced total water-soluble salts by 18% while modified biochar reduced them by 30.7%; for EX-Na + , unmodified biochar reduced it by 43.49% while modified biochar reduced it by 49.67%; and for ESP, unmodified biochar reduced it by 51.29% while modified biochar reduced it by 59.38%. However, modified and unmodified biochar did not show significant differences in improving other properties of saline soils. The addition of modified biochar increased soil nutrient content while altering the diversity and relative abundance of soil bacterial communities, enhancing the bacteria’s ability to synthesize and utilize soil nutrients. These results provide a basic scientific basis for the application of biochar in soil improvement in the Delta. 1. Introduction Soil salinization is a global problem Singh, 2021(), and saline soils have great potential for development, but currently less than 20 per cent of the total area is developed. Protecting, developing and improving saline and alkaline soils are of great significance in solving the food problem and realizing sustainable agricultural development Sahab et al., 2021(). Salinization in the Yellow River Delta is caused by a combination of geographic factors (short soil formation period, marine sediments, high evapotranspiration ratio, etc.) and human factors (irrational irrigation, mismatch of engineering, etc.), resulting in a serious salinization of about 4,657 km 2 of land (Mukhopadhyay et al., 2021). Salinization not only poisons plants and affects water-absorbing growth, but also reduces soil fertility and biodiversity, limiting agricultural productivity (Chang et al., 2019). Biochar as a soil amendment improves soil aeration due to its high specific surface area and porosity He et al., 2020(). The oxidation of its surface functional groups generates carboxyl and phenolic groups, which improve soil cation exchange capacity, nutrient retention and water holding capacity (Dey et al., 2023; Yuan et al., 2019) Torabian et al. (2021) experimentally found that the application of hydrothermal charcoal in different proportions by adding different layered amounts of hydrothermal charcoal to saline soils reduced Na + uptake by the plants, maintained ionic equilibrium, and lowered oxygen radicals under salinity stress through the addition of non-enzymatic antioxidant generation, reducing oxidative stress and protecting maize growth from salt toxicity. Shen et al. (2024) used corn stover hydrothermal charcoal to improve saline and alkaline land in the Songnen Plain, and by planting sorghum found that with the incorporation of biochar, they were able to effectively reduce soil pH, salinity, and Na + concentration, and improve soil water-holding capacity, nutrient content, and microbial diversity, which in turn increased sorghum yields. Similarly, Chen et al. (2022) applied hydrothermal charcoal to improve saline and alkaline land in the Songnen Plain, and found through incubation experiments that soil pH and alkalinity decreased, and soil effective nitrogen, effective phosphorus, and dissolved organic carbon increased with the addition of biochar. In summary, for soil salinization, there are still relatively few studies related to the application of hydrothermal charcoal to saline and alkaline land, and there is a lack of systematic discussion on the mechanism of action of biochar on the change of soil saline and alkaline properties, the relationship between soil physical properties, nutrients and bacterial communities (Niu et al., 2023). Therefore, in this study, the by-products of common crops were selected as raw materials, biochar was prepared hydrothermally using a reactor, and hydrothermal charcoal was modified by acidification, and through soil drenching experiments, the relationship between the modified biochar on the physical properties of saline-alkaline soils, saline-alkaline properties, bacterial communities, and bacterial community environments was combined with a detailed analysis of the mechanisms of hydrothermal charcoal in improving saline-alkaline soils to elucidate the effects and mechanisms of hydrothermal charcoal improvement, and the present study. It can provide theoretical basis and technical support for the application of hydrothermal charcoal in saline-alkaline soil improvement, and provide ideas for better utilization of biochar for saline-alkaline soil improvement. 2. Materials and Methods 2.1 Soil and crop collection and analysis Saline soils were taken from a village in Hekou District, Dongying City, Shandong Province, using an S-shaped line sampling, avoiding locations with high anthropogenic interference, such as field edges, shed edges and fertilizer piles. The soil was taken from the plow layer at a depth of 0-20 cm, and the whole layer was taken uniformly by the segmental method. The retrieved soil was spread in a plastic sheet and placed indoors in a ventilated area to dry out, removing stones, plant and animal residues and other debris, and crushing the larger pieces of soil. After air-drying, the soil was ground and mixed through a 2 mm sieve, and then put into a sealed bag for use. The basic physical and chemical properties of the saline soil in the Yellow River Delta were determined, and the results are shown in Table 1. The raw materials of biochar were taken from peanut shells, wheat straw, corn stalks and rice husks, which were agricultural wastes in Shandong Province, and washed with deionized water, dried, and ground (Xiao et al., 2020). 2.2 Preparation method of biochar The raw materials were mixed with water at a ratio of 1:20, placed in a reactor and ventilated with nitrogen, cooled down by water cooling at 240 °C for 2 h, filtered to collect the solid samples, and the samples were baked at 105 °C for 24 h. The samples were taken out, milled, and sieved to obtain hydrothermal peanut hulls biochar (FBC1), hydrothermal wheat straw biochar (FBC2), hydrothermal corn stover biochar (FBC3), and hydrothermal rice hulls biochar (FBC4). The dried biochar was immersed in an acid solution and stirred for 48 h. After extraction and filtration, the filtrate was rinsed with deionized water until the pH of the filtrate was stabilized, and finally dried in an oven at 105°C for 12 h, to obtain the modified hydrothermal charcoal FGBC1, FGBC2, FGBC3 and FGBC4 (Seikh et al., 2023; Xiao et al., 2020). 2.3 Soil washing test Different biochars were mixed with the treated saline soil at 5% addition and placed in flower pots and left to stand for 20 d Chen et al., 2024Yang et al., 2019(; ). Then, according to the summer rainfall (27 mm), small amounts of water were added from the top of the flower pots several times to ensure that the soil absorbed it completely, and the data were measured and analyzed after 10 d of resting, and the experiments were replicated three times in each group, with a control experiment. The pots were about 25 cm high, with holes at the bottom. Before filling the pots with soil, a screen was placed at the bottom, a gravel layer of about 2 cm high was laid to drain salt, and layers were laid to ensure uniformity when filling the pots, and the walls of the pots were coated with petroleum jelly to prevent edge effects with the soil. 2.4 Soil Property Analysis After the experiment, soil particle composition was measured using a laser particle size analyzer. Soil bulk density was determined by the ring knife method. Soil moisture content was measured using an electric blast drying oven (101-1AB, Test Instrument Co., Ltd., Tianjin, China) with the drying method. Zeta potential was analyzed using a nanoparticle size and Zeta potential analyzer (Malvern Zetasizer Nano ZS90, Malvern Instruments Ltd., UK). The total amount of water-soluble salts in the soil was measured using the residue drying method and ion summation method. Soil pH was measured with a pH meter (PHS-3E, Shanghai Instrument and Electrical Science Instrument Co., Ltd.). Soil cation exchange capacity (CEC) and EX-Na + were determined using a flame atomic absorption spectrophotometer (ICE 3500, Thermo Fisher Scientific). Total nitrogen content was measured using the Kjeldahl method. Available phosphorus was determined using the NaHCO 3 extraction-molybdenum antimony anti-spectrophotometry method. Soil organic matter was measured by the potassium dichromate method (external heating method). 2.5 Statistical Analysis Data analysis included one-way ANOVA, correlation, and principal component analysis using SPSS 20, with Duncan’s multiple range tests (p<0.05) conducted for significance. Results were presented as means ± standard deviation, with graphs created using Origin 2017. 3. Results and Discussion 3.1 Composition of Modified Biochar The prepared different biochars were measured by scanning electron microscopy, and the results are shown in Figure 1. It can be seen that the surface of hydrothermal carbon is relatively smooth, showing irregular elliptical particles and small particles. The structure is compact and easy to block. The specific surface area is small, the pore size is large, and there are almost no micropores. The specific surface area of biochar modified by phosphoric acid increases, the number of pores increases significantly, the pore size becomes larger, and the pore blockage is improved (Kalaiarasi et al., 2020; Ma et al., 2020). Phosphoric acid modified biochar will produce low molecular combinations such as steam. At the same time, phosphoric acid will dehydrate to produce polyphosphoric acid, which promotes the dehydration process of intramolecular and intermolecular in biochar. The generated steam will enter the interior of biomass polymer and promote the formation of biochar pore structure Chu et al., 2018(). Figure 2 is the Fourier transform infrared spectrum of hydrothermal carbon and modified hydrothermal carbon. The FTIR spectrum is analyzed as a whole : the absorption peak near 3425 cm -1 is the formation of -OH stretching vibration in carboxyl and phenolic groups Hidayat et al., 2020(), and the absorption peaks near 2924−2927 cm -1 , 2856−2860 cm -1 , 1439−1455 cm -1 , 1376−1382 cm -1 are considered to be the formation of aliphatic C-H stretching vibration of cellulose (Bakri et al., 2019; Natsir et al., 2022), lignin and other polymer. The peaks at 1730−1734 cm -1 and 1612−1615 cm -1 are the C=O and C=C peaks on the ester groups. The C=C ring stretching vibration of lignin is formed at 1513 cm -1 (Agarwal and Chemistry, 2019). The C-O peaks of hemicellulose and cellulosic alcohols are formed near 1159-1163 cm -1 , and the C-H stretching vibration of aromatic carbon is formed near 788−881 cm -1 (Supian et al., 2018). Compared with the spectra before modification, it can be found that the peak near 1085 cm -1 increases with the increase of the concentration of phosphoric acid modified solution. The absorption peaks of P=O and P-O in P-O-C and P=OOH are obtained by consulting the literature (Salehi et al., 2020). It was attributed to the ionization of P + -O and the symmetric vibration of P-O-P, indicating that the phosphoric acid modification increased the phosphate group of biochar. Further analysis showed that the intensity of the original C=O peak on the surface of the modified hydrothermal carbon increased, which indicated that the phosphoric acid modification made the biochar oxidized, the oxygen-containing functional groups increased, and the adsorption capacity increased (Ge et al., 2022). 3.2 Effect of modified charcoal on soil properties 3.2.1 Effects of modified biochar on ρb and porosity of saline-alkali soil Figure 3(a) is the effect of different biochar treatments on ρb and porosity. According to the diagram, the ρb of the original soil is about 1.337 g·cm -3 , the compaction is serious, the porosity is 49.5%, and the permeability is poor. The addition of modified biochar to the soil significantly reduced soil bulk weight, increased soil porosity, and improved soil permeability Liang et al., 2021(), but there was no significant difference in the effect of each treatment. The treatment effect of modified biochar was similar to that of unmodified biochar. After adding modified biochar to the soil, the soil ρb was significantly reduced and the soil porosity was increased. The treatment of modified hydrothermal biochar FGBC1, FGBC2, FGBC3 and FGBC4 decreased the soil ρb by about 0.120 g·cm -3 ,0.123 g·cm -3 ,0.135 g·cm -3 and 0.131 g·cm -3 , respectively, and increased the soil porosity by about 4.51%, 4.60%, 5.09% and 4.92%, respectively. The effects of different modified biochar treatments were similar. The effect of modified biochar on reducing ρb was slightly higher than that before modification, and soil porosity was further improved, but there was no significant change. The main reason was that phosphoric acid modification increased the specific surface area and porosity of biochar, which could further reduce ρb density, improve soil structure and make soil salt sink more easily after adding it to saline-alkali soil. 3.2.2 Effect of modified biochar on water content of saline-alkali soil The moisture content of saline-alkali soil was measured, and the results are shown in Figure 3(b). Different biochar treatments significantly increased soil moisture content, and there was no significant difference in the treatment effect of various biochars. FBC1, FBC2, FBC3 and FBC4 treatments increased soil water content by about 2.38%, 3.03%, 2.90% and 2.29%, respectively. Different modified biochar treatments significantly increased the soil moisture content, but the treatment effects were similar. The modified hydrothermal carbon FGBC1, FGBC2, FGBC3, and FGBC4 treatments increased the soil moisture content by about 1.80%, 2.78%, 2.37%, and 2.74%, respectively. The reason may be that the addition of biochar reduces the ρb, increases the soil porosity, and improves the soil pore structure. Another reason may be that the biochar has a small particle size and a large specific surface area. After being added to the soil, the specific surface area of the soil is increased, thereby increasing the soil water retention capacity (Razzaghi, Obour and Arthur, 2020). 3.2.3 Effect of modified biochar on the total amount of water-soluble salts in saline-alkali soil After the experiment, the total amount of water-soluble salt in saline-alkali soil was measured. The results are shown in Figure 3(c). It can be seen that the salt content of the original saline-alkali soil decreased from about 8.19 g·kg -1 to about 7.40 g·kg -1 after leaching. After adding different biochars, the soil salt content decreased significantly, but the change range was different. Compared with the original saline-alkali soil, FBC1, FBC2, FBC3 and FBC4 treatments reduced the soil salt content by about 23.03%, 13.86%, 14.89% and 20.20%, respectively. For the modified biochar, FGBC1, FGBC2, FGBC3 and FGBC4 treatments reduced the soil salt content by 28.84%, 30.09%, 32.29% and 31.58%, respectively, and the effect was significant. Compared with the unmodified hydrothermal carbon treatment, it increased by 1.31%, 2.56%, 4.77% and 4.05%, respectively. There was a significant difference in the treatment effect before and after modification. The reason for the decrease of soil salinity may be that on the one hand, the addition of biochar to the soil changes the particle size composition of the soil, reduces the soil bulk density, increases the soil porosity, improves the soil structure, makes the soil water conductivity stronger, lets more salt ions sink with the leaching water, thereby reducing the total amount of soil water-soluble salt ; on the other hand, biochar itself has an adsorption effect, which can adsorb and fix salt ions such as Na + in the soil (Awan, Ippolito and Ullman, 2021), further reducing the soil salt content. 3.2.4 Effect of modified biochar on pH of saline-alkali soil Figure 3(d) is the pH of the original soil and the soil after different biochar treatments. From the diagram, it can be seen that the addition of hydrothermal carbon has a relatively small effect on pH. FBC1, FBC2, FBC3 and FBC4 treatments increased the soil pH value by about -0.003%, 0.005%, 0.004% and 0.007%, respectively. The modified biochar obtained by modifying biochar with phosphoric acid has a higher reduction effect on soil pH, but the treatment effect before and after modification has little change. The reason for the decrease of soil pH may be that biochar is oxidized after being added to saline-alkali soil, and its surface acidic functional groups increase, which has electrostatic attraction with soil cations (Yang et al., 2021), thus reducing the pH value of soil. 3.2.5 Effects of modified biochar on CEC, EX-Na + and ESP After the experiment, the CEC of the soil was measured. The results are shown in the figure. It can be seen from the figure that the addition of biochar significantly increased the CEC of the soil. The treatments of FBC1, FBC2, FBC3 and FBC4 increased the absolute value of soil CEC by about 23.12%, 13.83%, 15.35% and 12.44%, respectively. Figure 3(e) is the treatment effect of modified biochar. It can be seen that different modified hydrothermal carbons increase soil CEC, among which FGBC1, FGBC2, FGBC3 and FGBC4 treatments increase soil CEC by about 23.56%, 24.82%, 23.42% and 23.51%, respectively. Compared with the unmodified hydrothermal carbon treatment, soil CEC increased by about 1.12%, 2.38%, 0.98% and 1.52%, and the effect before and after modification did not change significantly. The increase of soil cation exchange capacity may be due to the large specific surface area and high surface charge density of biochar Kharel et al., 2019(). At the end of the experiment, EX-Na + in saline-alkali soil was measured, and the results were shown in Figure 3(f). It can be seen that FBC1, FBC2, FBC3 and FBC4 treatments reduced EX-Na + by about 45.31%, 43.06%, 38.84% and 46.74%, respectively. FGBC1, FGBC2, FGBC3 and FGBC4 treatments reduced EX-Na + by about 45.89%, 50.51%, 51.39% and 50.90%, respectively. Compared with the unmodified hydrothermal carbon treatment, EX-Na + decreased by about 1.06%, 4.73%, 5.61% and 5.12%. Except for FGBC1, the effect before and after modification changed significantly. The reason for the decrease of EX-Na + after phosphoric acid modification is that phosphoric acid modification changes the pore structure of biochar, increases the specific surface area of biochar, enhances the adsorption performance of biochar, and further decreases EX-Na + (Chen et al., 2021). The ESP of saline-alkali soil was calculated, and the results were shown in Figure 3(g). It can be seen that the addition of biochar reduced soil ESP, and FBC1, FBC2, FBC3 and FBC4 treatments reduced soil ESP by about 55.58%, 49.98%, 46.98% and 52.63%, respectively. For the modified biochar, FGBC1, FGBC2, FGBC3, and FGBC4 treatments reduced soil ESP by about 56.21%, 60.36%, 60.62%, and 60.4%, respectively. Compared with the unmodified hydrothermal carbon treatment, soil ESP was reduced by about 0.22%, 2.00%, 2.11%, and 2.01%. Except for FGBC1, the effect before and after modification changed greatly. The biochar before and after modification had little effect on soil CEC, but compared with before modification, the modified biochar was able to improve the specific surface area and pore structure of the biochar, making it more suitable for adsorption of sodium ions, and thus the modified biochar further reduced EX-Na + , which in turn reduced the soil ESP (El-Sharkawy et al., 2022). 3.2.6 Effect of modified biochar on organic matter in saline-alkali soil After the experiment, the organic matter content of saline-alkali soil was measured, and the results are shown in Figure 3(h). Compared with the organic matter content of about 7.79 mg·kg -1 in the original saline-alkali soil, the addition of biochar to the soil significantly increased the organic matter content in the soil. FBC1, FBC2, FBC3 and FBC4 treatments increased the organic matter content in the soil by about 1.87 times, 1.27 times, 1.21 times and 1.62 times, respectively. Similarly, the organic matter content in the soil after different modified hydrothermal carbon treatments was significantly increased. FGBC1, FGBC2, FGBC3, and FGBC4 treatments increased the organic matter content in the soil by 1.79 times, 1.76 times, 1.82 times, and 1.93 times, respectively. Similar to before modification, there was no significant difference in the effect of biochar on the increase of soil organic matter content before and after modification. Biochar has an adsorption effect on organic matter in soil, which can slow down the mineralization of organic matter. Therefore, the addition of biochar makes the soil have higher organic matter (Zheng et al., 2021). 3.3 Effect of modified biochar on salt ion content and SAR 3.3.1 Effect on salt ion content and SAR The ion addition method was used to determine the salt content of the soil after FGBC3 treatment and the original saline-alkali soil, that is, the eight salt ions were measured one by one. The results are shown in Table 2. It can be seen that the content of Na + and Cl - in the original saline-alkali soil is the highest, about 2.630 g·kg -1 and 4.401 g·kg -1 , respectively, and the content of other salt ions is low, so Na + and Cl - are the main salt ions. The addition of modified biochar significantly decreased the content of main saltions and soil salt content. FGBC3 decreased the content of Na + and Cl - in saline-alkali soil by about 48.10% and 55.65%, respectively. The addition of modified biochar also increased the content of K + , Ca 2+ and Mg 2+ in soil, and significantly reduced soil SAR, indicating that it had a good improvement effect on saline-alkali soil, improved the sodium structure of soil, and reduced the ion stress of soil Na + . 3.3.2 Effect on nutrient content of saline-alkali soil The contents of available potassium, total nitrogen, available phosphorus and organic matter in FGBC3 treated and original saline-alkali soil were determined. The results are shown in Table 2. It can be seen that compared with the original saline-alkali soil, the addition of modified biochar increased the content of soil nutrients to varying degrees. FGBC3 treatment increased the available potassium content by 33.74%, the total nitrogen content by 44.36%, the available phosphorus content by 142.73%, and the organic matter content by 1.83 times. Biochar itself contains organic matter and C, N, P, K and other nutrient elements (Mujtaba et al., 2021). After being added to the soil, the soil nutrient properties are improved. At the same time, phosphoric acid modification increases the specific surface area and porosity of biochar, enhances the adsorption capacity, and its adsorption can also reduce the nutrient loss caused by leaching (Li et al., 2021). It is more conducive to the maintenance of soil nutrients, which in turn improves the soil nutrient environment and is conducive to the improvement of saline-alkali soil. 3.4 Effect of modified biochar on bacteria community in saline-alkali soil 3.4.1 Effects on the diversity of bacterial communities in saline soils The alpha diversity of FGBC3-treated soil was analyzed, and the data were shown in Table 3. It can be seen that FGBC3 treatment effectively increased the Chao1 and Observed species index and increased the richness of bacterial communities. At the same time, FGBC3 treatment increased the Shannon index / Simpson index value, indicating that its treatment increased the diversity of bacterial communities. The change of Pielou’s evenness index indicated that the addition of modified biochar to the soil increased the uniformity of soil bacterial community. The Good’s coverage index of all treatments was greater than 99%, indicating that the test results can better reflect the real situation in the soil. This also shows that biochar as an organic modifier, its addition can not only increase soil carbon storage, but also increase soil biological activity (Che, Li and Zhang, 2021). 3.4.2 Effects on bacterial community structure in saline-alkali soil Before and after the treatment of modified biochar, the bacterial community in saline-alkali soil was mainly distributed in 11 phyla, and the addition of modified biochar had a significant effect on the relative abundance of these phyla. From Figure 4, it can be seen that the addition of modified biochar affected the composition of the soil bacterial community, the addition of FGBC3 increased the relative abundance of Actinobacteria, Bacillus, Green Benders, and Acidobacteria in the soil by 19.41%, 7.39%, 7.28%, and 5.53%, respectively, and decreased the relative abundance of Ascomycetes, Thick-walled Bacteria, and Bacteroidetes by 23.37%, 13.51%, and 4.61%, respectively, which reflected the selective effect of biochar on soil bacterial community and helped to enhance the microbial community with organic matter decomposition, nutrient cycling and environmental adaptability. Proteobacteria was the main dominant phylum, represented by genera such as Pseudomonas and Rhizobium, involved in nitrogen cycle and nutrient transformation, but its abundance decreased slightly after adding biochar, indicating that other flora were more competitive in the improved environment. The abundance of Actinobacteria increased significantly, and the increase of Streptomyces enhanced the decomposition ability of soil organic matter and helped to improve fertility. The bacteria of Gemmatimonadetes have strong adaptability to barren and arid environments. Biochar provides a more suitable environment by improving soil porosity and water retention capacity, making it more advantageous in improving soil. The abundance of Chloroflexi has also increased, and its representative genus, such as Flavobacterium, has the ability to degrade organic matter. The improved environment of biochar is conducive to carbon cycle. Acidobacteria preferred acidity, but the abundance increased in the modified soil, which may be due to the reduction of saline-alkali stress by biochar, so that the azotobacter genus can better play the role of nitrogen fixation and improve the soil nitrogen cycle. In addition, the abundance of Bacillus in Firmicutes decreased slightly after treatment, but its saline-alkali tolerance still had a positive effect on soil. Flavobacterium of Bacteroidetes was effective in the degradation of organic matter, but its abundance decreased slightly after treatment due to the enhanced competitiveness of other bacteria. In summary, the modified biochar optimized the soil bacterial community structure, increased the abundance of bacteria with the function of decomposing organic matter and nutrient cycling, and improved the soil improvement effect and ecological environment. 3.4.3 Effects on PICRUSt function prediction of bacteria in saline-alkali soil From Figure 5, the main functions of bacteria in saline-alkali soil of the Yellow River Delta include cofactors, prosthetic groups, electron carriers and vitamin biosynthesis, amino acid biosynthesis, nucleoside and nucleotide biosynthesis, fatty acid and lipid biosynthesis, carbohydrate biosynthesis, fermentation, trichloroethylene cycle, cell structure biosynthesis, etc. After FGBC3 treatment, the predicted relative abundance of nucleoside and nucleotide biosynthesis, amino acid biosynthesis, carbohydrate biosynthesis and other metabolic functions of saline-alkali soil bacteria increased significantly, and the predicted relative abundance of carbohydrate degradation, aromatic compound degradation and other metabolic functions of soil bacteria decreased significantly. This may be due to the strong stability of modified biochar, which is not easy to degrade after adding saline-alkali soil. The overall change was similar, and the relative rich predictive value of bacterial biosynthesis increased significantly, indicating that the addition of modified biochar slowed down the effect of saline-alkali stress on soil bacterial metabolic activity, enhanced the function of bacterial synthesis and utilization of soil nutrients, and improved the soil nutrient environment Wang et al., 2022(), which was conducive to the improvement of saline-alkali soil. 4.Conclusion The addition of biochar can improve the soil structure, reduce the bulk density, increase the porosity and water content, and promote the sinking of salts with the drench water. In addition, biochar, with its large specific surface area and well-developed pore structure, can effectively adsorb salt ions, reducing soil salt content by about 25% and improving soil properties by increasing soil CEC and organic matter content, thereby reducing ESP and enhancing soil buffering and looseness. Compared with ordinary biochar, phosphoric acid-modified biochar can neutralize the alkaline components in soil, enhance the adsorption capacity of salts, make salts sink more easily with water, and have stronger adsorption effect on ions such as Na + , Cl - , etc., so that the content of Na + and Cl - in the saline soil decreased by about 48.1% and 55.65%, respectively, and its effective relief of saline stress. The addition of modified biochar also increased the soil nutrient content, which was significantly negatively correlated with saline soil characteristics, indicating that the soil environment was improved. Meanwhile, modified biochar changed the diversity and relative abundance of soil bacterial communities and enhanced the function of bacteria in utilizing soil nutrients, of which the increase of acidic phylum and the decrease of thick-walled phylum further proved that the soil salinity was improved. Acknowledgments The authors gratefully acknowledge Key R&D Program of Shandong Province, China (2022TZXD0044). Reference Agarwal, U. P., Ralph, S. A., Padmakshan, D., Liu, S., & Foster, C. E. (2019). Estimation of Syringyl Units in Wood Lignins by FT-Raman Spectroscopy. Journal of Agricultural and Food Chemistry, 67 (15), 4367-4374. https://doi.org/10.1021/acs.jafc.8b06707 Atkinson, C. J., Fitzgerald, J. D., & Hipps, N. A. (2010). Potential mechanisms for achieving agricultural benefits from biochar application to temperate soils: a review. Plant and Soil, 337 (1-2), 1-18. https://doi.org/10.1007/s11104-010-0464-5 Awan, S., Ippolito, J. A., Ullman, J. L., Ansari, K., Cui, L. Q., & Siyal, A. A. (2021). Biochars reduce irrigation water sodium adsorption ratio. Biochar, 3 (1), 77-87. https://doi.org/10.1007/s42773-020-00073-z Bakri, M. K. B., Rahman, M. R., Hamdan, S., Khui, P. L. N., & Kakar, A. (2019). Infrared Spectral Functional Group and Thermal Properties of Acacia Wood Bio-composites. Engineering materials . https://doi.org/10.1007/978-3-030-29627-8_6 Cao, X. D., & Harris, W. (2010). Properties of dairy-manure-derived biochar pertinent to its potential use in remediation. Bioresource Technology, 101 (14), 5222-5228. https://doi.org/10.1016/j.biortech.2010.02.052 Chang, X. M., Gao, Z. Y., Wang, S. L., & Chen, H. R. (2019). Modelling long-term soil salinity dynamics using SaltMod in Hetao Irrigation District, China. Computers and Electronics in Agriculture, 156 , 447-458. https://doi.org/10.1016/j.compag.2018.12.005 Che, Q. J., Li, M., & Zhang, Z. S. (2021). Effects of Biochar Application on Soil Organic Carbon in Degraded Saline-sodic Wetlands of Songnen Plain, Northeast China. Chinese Geographical Science, 31 (5), 877-887. https://doi.org/10.1007/s11769-021-1232-6 Chen, Y., Ning, P., Miao, R. R., He, L., & Guan, Q. Q. (2021). Resource utilization of agricultural residues: one-step preparation of biochar derived from Pennisetum giganteum for efficiently removing chromium from water in a wide pH range. Environmental Science and Pollution Research, 28 (48), 69381-69392. https://doi.org/10.1007/s11356-021-15388-y Chen, Y. H., Sun, Z. X., Su, Y. J., Yang, J. X., Li, M. T., Hong, B., & Chen, G. (2022). Hydrochar Derived from Spent Mushroom Substrate Ameliorates Soil Properties and Nutrient Levels in Saline-Sodic Soil: An Incubation Study. Sustainability, 14 (20), 12. https://doi.org/10.3390/su142012958 Chu, G., Zhao, J., Huang, Y., Zhou, D. D., Liu, Y., Wu, M., Peng, H. B., Zhao, Q., Pan, B., & Steinberg, C. E. W. (2018). Phosphoric acid pretreatment enhances the specific surface areas of biochars by generation of micropores. Environmental Pollution, 240 , 1-9. https://doi.org/10.1016/j.envpol.2018.04.003 Dey, S., Purakayastha, T. J., Sarkar, B., Rinklebe, J., Kumar, S., Chakraborty, R., Datta, A., Lal, K., & Shivay, Y. S. (2023). Enhancing cation and anion exchange capacity of rice straw biochar by chemical modification for increased plant nutrient retention. Science of the Total Environment, 886 , 14. https://doi.org/10.1016/j.scitotenv.2023.163681 El-Sharkawy, M., El-Naggar, A. H., Al-Huqail, A. A., & Ghoneim, A. M. (2022). Acid-Modified Biochar Impacts on Soil Properties and Biochemical Characteristics of Crops Grown in Saline-Sodic Soils. Sustainability, 14 (13), 21. https://doi.org/10.3390/su14138190 Ge, Q. L., Tian, Q., Wang, S. F., Zhang, J., & Hou, R. (2022). Highly Efficient Removal of Lead/Cadmium by Phosphoric Acid-Modified Hydrochar Prepared from Fresh Banana Peels: Adsorption Mechanisms and Environmental Application. Langmuir, 38 (49), 15394-15403. https://doi.org/10.1021/acs.langmuir.2c02693 He, L. L., Zhao, J., Yang, S. M., Zhou, H., Wang, S. Q., Zhao, X., & Xing, G. X. (2020). Successive biochar amendment improves soil productivity and aggregate microstructure of a red soil in a five-year wheat-millet rotation pot trial. Geoderma, 376 , 9. https://doi.org/10.1016/j.geoderma.2020.114570 Hidayat, S., Rohmani, L., Adiperdana, B., Faizal, F., Hartati, Y. W., & Rahayu, I. J. K. E. M. (2020). Synthesis of Carboxymethyl Cellulose Form Banana Stems and its Characterization for Anode Binder of Li-Ion Battery. Key engineering materials, 860 . https://doi.org/10.4028/www.scientific.net/kem.860.59 Kalaiarasi, R., Parameswari, E., Davamani, V., & Sharmila, D. J. S. (2020). Exploring the Potential of Biochar Activated with Phosphoric Acid towards Hexavalent Chromium Removal. International Research Journal of Pure and Applied Chemistry . https://doi.org/10.9734/irjpac/2020/v21i2030278 Kharel, G., Sacko, O., Feng, X., Morris, J. R., Phillips, C. L., Trippe, K., Kumar, S., & Lee, J. W. (2019). Biochar Surface Oxygenation by Ozonization for Super High Cation Exchange Capacity. Acs Sustainable Chemistry & Engineering, 7 (19), 16410-16418. https://doi.org/10.1021/acssuschemeng.9b03536 Li, Q., Yu, W., Guo, L. W., Wang, Y. H., Zhao, S. Y., Zhou, L., & Jiang, X. H. (2021). Sorption of Sulfamethoxazole on Inorganic Acid Solution-Etched Biochar Derived from Alfalfa. Materials, 14 (4), 15. https://doi.org/10.3390/ma14041033 Liang, J. P., Li, Y., Si, B. C., Wang, Y. Z., Chen, X. G., Wang, X. F., Chen, H. R., Wang, H. R., Zhang, F. C., Bai, Y. G., & Biswas, A. (2021). Optimizing biochar application to improve soil physical and hydraulic properties in saline-alkali soils. Science of the Total Environment, 771 , 15. https://doi.org/10.1016/j.scitotenv.2020.144802 Ma, Y. F., Li, P., Yang, L., Wu, L., He, L. Y., Gao, F., Qi, X. B., & Zhang, Z. L. (2020). Iron/zinc and phosphoric acid modified sludge biochar as an efficient adsorbent for fluoroquinolones antibiotics removal. Ecotoxicology and Environmental Safety, 196 , 10. https://doi.org/10.1016/j.ecoenv.2020.110550 Mujtaba, G., Hayat, R., Hussain, Q., & Ahmed, M. (2021). Physio-Chemical Characterization of Biochar, Compost and Co-Composted Biochar Derived from Green Waste. Sustainability, 13 (9), 22. https://doi.org/10.3390/su13094628 Mukherjee, A., & Zimmerman, A. R. (2013). Organic carbon and nutrient release from a range of laboratory-produced biochars and biochar-soil mixtures. Geoderma, 193 , 122-130. https://doi.org/10.1016/j.geoderma.2012.10.002 Mukhopadhyay, R., Sarkar, B., Jat, H. S., Sharma, P. C., & Bolan, N. S. (2021). Soil salinity under climate change: Challenges for sustainable agriculture and food security. Journal of Environmental Management, 280 , 14. https://doi.org/10.1016/j.jenvman.2020.111736 Natsir, M., Pratiwi, A. M., Azis, T., Nohong, Imran, Harlis, W. O., Alimin, Kadidae, L. O., Ruslan, & Bijang, C. (2022). Efektivitas Fotodegradasi Lignin dari Limbah Ampas Sagu (Metroxylon sagu Rottb.) Menggunakan Katalis TiO. KOVALEN Jurnal Riset Kimia . https://doi.org/10.22487/kovalen.2022.v8.i3.16149 Niu, P. F., Han, Z. J., Li, K. C., Lv, L. X., & Guo, P. (2023). The 2022/1/1w 6.7 Menyuan Earthquake on the Northeastern Margin of the Tibetan Plateau, China: Complex Surface Ruptures and Large Slip. Bulletin of the Seismological Society of America, 113 (3), 976-996. https://doi.org/10.1785/0120220163 Razzaghi, F., Obour, P. B., & Arthur, E. (2020). Does biochar improve soil water retention? A systematic review and meta-analysis. Geoderma, 361 , 10. https://doi.org/10.1016/j.geoderma.2019.114055 Sahab, S., Suhani, I., Srivastava, V., Chauhan, P. S., Singh, R. P., & Prasad, V. (2021). Potential risk assessment of soil salinity to agroecosystem sustainability: Current status and management strategies. Science of the Total Environment, 764 , 15. https://doi.org/10.1016/j.scitotenv.2020.144164 Salehi, E., Askari, M., Velashjerdi, M., & Arab, B. (2020). Phosphoric acid-treated Spent Tea Residue Biochar for Wastewater Decoloring: Batch Adsorption Study and Process Intensification using Multivariate Data-based Optimization. Chemical Engineering and Processing-Process Intensification, 158 , 15. https://doi.org/10.1016/j.cep.2020.108170 Seikh, A. H., Alharbi, H. F., Alnaser, I. A., Karim, M. R., Mohammed, J. A., Aijaz, M. O., Hassan, A., & Abdo, H. S. (2023). Study on Process Parameters in Hydrothermal Liquefaction of Rice Straw and Cow Dung: Product Distribution and Application of Biochar in Wastewater Treatment. Processes, 11 (9), 17. https://doi.org/10.3390/pr11092779 Shen, J., Jiang, Z. L., Tang, Z. C., Guo, F. K., Shao, H. Y., & Ruan, X. X. (2024). Hydrochar Utilization for Saline-Alkali Soil Amelioration and Its Carbon Sequestration Potential Assessment. Advanced Sustainable Systems, 8 (12), 12. https://doi.org/10.1002/adsu.202400290 Shen, R. X., Lu, J. W., Yao, Z. L., Zhao, L. X., & Wu, Y. L. (2021). The hydrochar activation and biocrude upgrading from hydrothermal treatment of lignocellulosic biomass. Bioresource Technology, 342 , 12. https://doi.org/10.1016/j.biortech.2021.125914 Singh, A. (2021). Soil salinization management for sustainable development: A review. Journal of Environmental Management, 277 , 15. https://doi.org/10.1016/j.jenvman.2020.111383 Supian, M. A. F., Amin, K. N. M., Jamari, S. S., & Mohamad, S. (2018). Investigation on pre-treatment process in microcrystalline cellulose (MCC) from oil palm empty fruit bunch (EFB). Journal of Chemical Engineering and Industrial Biotechnology (1). https://doi.org/10.15282/JCEIB.V3I1.3877 Xiao, L., & Meng, F. D. (2020). Evaluating the effect of biochar on salt leaching and nutrient retention of Yellow River Delta soil. Soil Use and Management, 36 (4), 740-750. https://doi.org/10.1111/sum.12638 Yang, R. Y., Zhou, C. X., Zhu, J. J., Pan, Y. H., Sun, J. N., & Zhang, Z. H. (2019). Effects of biochar application on phreatic water evaporation and water-salt distribution in coastal saline soil. Journal of Plant Nutrition, 42 (10), 1243-1253. https://doi.org/10.1080/01904167.2019.1605379 Yang, X., Pan, H., Shaheen, S. M., Wang, H. L., & Rinklebe, J. (2021). Immobilization of cadmium and lead using phosphorus-rich animal-derived and iron-modified plant-derived biochars under dynamic redox conditions in a paddy soil. Environment International, 156 , 10. https://doi.org/10.1016/j.envint.2021.106628 Yuan, P., Wang, J. Q., Pan, Y. J., Shen, B. X., & Wu, C. F. (2019). Review of biochar for the management of contaminated soil: Preparation, application and prospect. Science of the Total Environment, 659 , 473-490. https://doi.org/10.1016/j.scitotenv.2018.12.400 Zheng, X. D., Li, X., Singh, B. P., Wei, L., Huang, L. X., Huang, Y. F., Huang, Q., Chen, X. B., Su, Y. R., Liu, Z. Z., & Wang, H. L. (2021). Biochar protects hydrophilic dissolved organic matter against mineralization and enhances its microbial carbon use efficiency. Science of the Total Environment, 795 , 9. https://doi.org/10.1016/j.scitotenv.2021.148793 Supplementary Material File (image.docx) Download 7.91 MB File (table.docx) Download 26.12 KB Information & Authors Information Version history V1 Version 1 25 February 2025 Peer review timeline Published Plant and Soil Version of Record 11 Jun 2025 Published Copyright This work is licensed under a Non Exclusive No Reuse License. Keywords biochar phosphoric acid modification saline-alkaline soil soil properties the yellow river delta Authors Affiliations Shuo Yang View all articles by this author Yujun Ma 0009-0007-9689-3921 Shandong Jianzhu University View all articles by this author Metrics & Citations Metrics Article Usage 161 views 120 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Shuo Yang, Yujun Ma. Effects of hydrothermal charcoal on saline-alkaline soil properties in the Yellow River Delta. Authorea . 25 February 2025. DOI: https://doi.org/10.22541/au.174048710.05206800/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu . 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