Artificial humic acid improves P availability via regulating P-cycling microbial communities for crop growth

A-HA (artificial humic acid) play essential roles to improve soil organic matter in agricultural soil, however, the relative mechanistic effects on soil phosphorus (P) transformation and availability resulting from stimulation of microbial activities and changes in microbial communities remain uncertain. This study investigated the responses of microbial communities in the rhizosphere, bulk soils, and unplanted soil with the combined application of A-HA and phosphate fertilizer to better understand the mechanisms by which A-HA affects P cycling.

Physical and chemical analyses, along with metagenomic methods, were employed to determine phosphorus availability and fractions, as well as to measure soil microbial diversity and the relative abundance of microbial P-cycling genes in bulk soil, rhizosphere soil, and unplanted soil subjected to varying levels of phosphorus fertilizer.

The findings demonstrated that application of A-HA and phosphate fertilizers directly increased soil Olsen P and unstable P levels and indirectly altered microorganism functional genes involved in soil P cycling. More interestingly, 28 macrogenomic assembled genomes (MAGs) were reconstructed, all of which contained P cycle-related genes with copy numbers ranging from 1 to 8. In addition, we evaluated the correlation among maize biomass, photosynthetic characteristics, plant P uptake, and P utilization efficiency (PUE) and stabilized soil P fractions. A-HA + P0.5 treatment appeared the most promising due to its higher sustainability yield index and agronomic efficiency.

Our results highlight the importance of A-HA in promoting changes in microbial functional genes involved in soil P cycling with different P levels.