The effects of different phosphorus supply levels on the organic acids, inorganic phosphorus, and microorganisms in the rhizosphere soil of switchgrass (Panicum virgatum L.)

This study aims to explore the effects of different phosphorus supply levels on soil organic acids, inorganic phosphorus, and microbial communities, as well as to investigate the microbial ecological characteristics in the rhizosphere. It holds significant importance for promoting soil phosphorus cycling. The experiment employed a randomized block design with the Alamo and Pathfinder varieties of Panicum virgatum L. as materials. Three phosphorus levels were set: P0 (0 kg·hm⁻²), P30(30 kg·hm⁻²), and P90(90 kg·hm⁻²), which to study the composition and content of rhizosphere soil organic acids, inorganic phosphorus, and microbial population diversity. The results showed that phosphorus levels had a significant impact on rhizosphere soil organic acids, inorganic phosphorus, and microbial communities. At different phosphorus levels, the Alamo variety exhibited a greater increase in rhizosphere soil organic acid content and had higher levels of rhizosphere soil inorganic phosphorus. In terms of microbial communities, both the Alamo and Pathfinder varieties showed similar patterns of change. Under the P30 and P90 treatments, the content of succinic acid, malic acid, maleic acid, and malonic acid in the rhizosphere soil significantly increased, while the content of suberic acid decreased. Additionally, the content of Ca₂-P, Al-P, Fe-P, O-P, and Ca₁₀-P in the rhizosphere soil significantly increased after phosphorus application. The Chao1 index, ACE index, Shannon index, and Simpson index of bacterial communities also significantly increased after phosphorus application, with the phyla Proteobacteria, Bacteroidetes, Actinobacteria, and Chloroflexi dominating at the phylum level. The comprehensive analysis found that under different phosphorus levels, the relationship between organic acids and inorganic phosphorus was not significant. The abundance and diversity of bacterial communities were jointly influenced by organic acids and inorganic phosphorus, and the relationships between dominant bacterial phyla and organic acids and inorganic phosphorus varied. In conclusion, the rhizosphere soil microecosystem composed of organic acids, inorganic phosphorus, and microorganisms were a harmonious system that played a positive role in the efficient utilization of phosphorus resources.