Cellulose and lignin regulate partitioning of soil phosphorus fractions and alkaline phosphomonoesterase encoding bacterial community in phosphorus-deficient soils

Crop straw retention is believed to effectively promote soil phosphorus (P) availability. However, little is known about how specific components of crop straw, such as cellulose and lignin, regulate soil P availability, which depends on several processes, including the reactions catalyzed by phosphomonoesterase activities. Of the genes encoding alkaline phosphomonoesterase, phoD are ubiquitous in soil. Here, we studied the effects of cellulose and lignin on soil P fractions and phoD-harboring bacterial community in P-deficient upland and paddy soils. In the upland soil, cellulose amendment significantly increased microbial P assimilation and decreased soil citrate-P and HCl-P fractions, suggesting that cellulose mediated the conversion of soil P fractions from the non-labile to the labile P pool (e.g., microbial P) via microbial enrichment. Lignin significantly increased soil Olsen-P content, but scarcely influenced P-related microbial parameters after incubation for 60 days. Therefore, lignin directly increased soil available P via competitive P adsorption by lignin functional groups, rather than by altering soil microbial processes. Compared to upland soil, a smaller effect of both cellulose and lignin on phoD gene abundance, alkaline phosphomonoesterase activity, and phoD-harboring bacterial community was observed in paddy soil, suggesting that the carbon inputs may be unable to promote organic P availability under oxygen-deficient conditions. Our results highlight the contrasting mechanisms of soil P availability regulation via cellulose or lignin in P-deficient soils.