Artificial humic acid improves maize growth and soil phosphorus utilization efficiency

Phosphorus is one of the largest nutrients limiting crop productivity. Humic substances, as macromolecular polymers, are potential carbon materials responsible for soil additives to increase soil phosphorus utilization and mitigate phosphorus loss. However, the effect of artificial humic substances (A-HS) on maize agronomic traits and soil phosphorus transformation in black soil areas has not been investigated, and the mechanisms by which it affects phosphorus utilization by seedlings remain unclear. In this study, phosphate fertilizer and A-HS are jointly applied to a model soil, and maize growth and the soil phosphorus availability are determined at various A-HS concentrations in greenhouses using the root-bag technique. Herein, A-HS includes artificial humic acid and fulvic acid with commercial humic acid for comparisons. Positive effects on agronomic traits and phosphorus uptake in maize seedlings were quantified. As A-HS also influences the soil microbiome, the present study further explored the changing trend of soil acid phosphatase and phoC gene community structure by high-throughput sequencing techniques, using the Illumina MiSeq platform with Functional Annotation of Uparse annotation, to provide insights into how A-HS affects microbially mediated phosphorus transformation. The study found a declining alpha diversity of phoC microbial communities in rhizosphere and bulk soil. A-HS affects the structure of maize rhizosphere and bulk soil microbial communities and enhances soil phosphorus effectiveness and nutrient uptake by maize. As a general result, this study supports that the application of artificial humic acid in sustainable farming techniques can not only increase phosphorus availability in farmland but also stimulate the formation of a healthy soil microbiome.