Organic carbon inputs shift the profiles of phosphorus cycling-related genes in maize rhizosphere

Soil microbiome is the key driver mediating soil P transformation in agroecosystems. However, the underlying genomic information related to soil P cycling in response to organic C inputs is largely unknown.

By using metagenomic sequencing, we investigated the effect of P fertilization and C input (i.e., glucose and lignin) on functional profiles of microbial genes related to P cycling in bulk and rhizosphere soils. Maize plants were grown for 47 days in Ultisols with or without P-fertilizer history.

Glucose decreased rhizosphere H₂O-P_i concentrations in soil with P history, increased that in soil without P history; while lignin increased that in both soils. Ogranic C inputs increased the relative abundances of phnGHIJLMNP and pit genes by 17–138% and 2.3–31%, decreased those of phoB, phoR and pstABCS genes by 3.6–18%, 12–31% and 11–26%, respectively, in rhizosphere soils irrespective of P history. In the rhizosphere rather than bulk soil, the proportion of P starvation regulation-related genes was higher in lignin treated-soils without than with P history. Proteobacteria (10–89%) and Acidobacteria (0.41–57%) were the dominant phyla and main contributors to soil P transformation-related genes (e.g., appA, phoAD, gcd). Elevated soil pH induced by organic C inputs also diversified the composition of genes involved in P transformation.

Organic C altered P cycling-related gene composition irrespective of soil P status, which facilitated P transformation. Proteobacteria and Acidobacteria were vital in mediating C and P metabolisms.