The phosphoric acid extract of fresh biochar and its compound aqueous solutions promoted tobacco plant growth by regulating nutrient-related microorganisms in rhizosphere soil (bacterial)

Biochar has been widely used in agriculture and has positive effects on soil improvement. To further explore the biochar soil plant interaction mechanisms, rice husk biochar and root-promoting solutions were used to prepare biochar extracts and compound aqueous solutions, to study the effects of biochar acid extract and its compound aqueous solutions on main nutrients content (nitrogen, phosphorus, potassium), microbial abundance and functional diversity in tobacco rhizosphere soil, and their regulation on the growth of flue-cured tobacco. In this paper, the results showed that, applying biochar acid extract and Its compound aqueous solutions at different concentrations significantly enhanced tobacco plant dry matter accumulation, improved soil pH, increased available nitrogen and organic matter, and reduced potassium and phosphorus availability. Notably, the compound aqueous solutions had a more pronounced effect on soil nutrients compared to biochar acid extract. Regarding the microbial community structure, biochar acid extract and compound aqueous solutions increased the relative abundance of specific bacterial genera, including Sphingomonas and Vicinamibacteraceae, and fungal genera such as Mortierella and Penicillium. biochar acid extract and compound aqueous solutions positively influenced functional groups like chemoheterotrophs, aerobic chemoheterotrophs, and saprotrophs. Sphingomonas contributes to regulating soil pH and decomposing various organic compounds, while Vicinamibacteraceae play a critical role in nitrogen cycling and nutrient availability. The saprotrophic fungus Mortierella can release organic acids to solubilize phosphorus in soils, and Penicillium enhance phosphorus cycling and availability, improving soil nutrient content. Additionally, the application of biochar acid extract and compound aqueous solutions increased the complexity and interconnectivity of the soil microbial network.

生物炭（Biochar）已在农业领域得到广泛应用，对土壤改良具有积极作用。为进一步探明生物炭-土壤-植物的互作机制，本研究以稻壳生物炭和促根溶液为原料制备生物炭提取物与复合水溶液，旨在探究生物炭酸提取物及其复合水溶液对烟株根际土壤主要养分含量（氮、磷、钾）、微生物丰度与功能多样性的影响，及其对烤烟生长的调控作用。研究结果表明，施加不同浓度的生物炭酸提取物及其复合水溶液，可显著提升烟株干物质积累量，改善土壤pH值，提高有效氮与有机质含量，同时降低钾、磷的有效性。值得注意的是，相较于单一的生物炭酸提取物，复合水溶液对土壤养分的调控效果更为显著。就微生物群落结构而言，生物炭酸提取物及其复合水溶液可提升特定细菌类群的相对丰度，包括鞘氨醇单胞菌属（Sphingomonas）与维奇诺菌科（Vicinamibacteraceae），以及被孢霉属（Mortierella）、青霉属（Penicillium）等真菌类群。生物炭酸提取物及其复合水溶液对化能异养型微生物（chemoheterotrophs）、好氧化能异养型微生物（aerobic chemoheterotrophs）及腐生营养型微生物（saprotrophs）等功能菌群具有正向调控作用。鞘氨醇单胞菌属可调控土壤pH并分解多种有机物质，而维奇诺菌科在氮循环与养分有效性调控中发挥关键作用；腐生真菌被孢霉属可通过释放有机酸溶解土壤中的磷素，青霉属则能促进磷循环并提升其有效性，进而改善土壤养分含量。此外，施加生物炭酸提取物及其复合水溶液可提升土壤微生物网络的复杂度与连通性。