Metagenomics reveals functional profiles of soil nitrogen and phosphorus cycling under different amendments in saline-alkali soil.

High salinity, low fertility and poor structure in saline-alkali soils led to nutrient cycling slow and microbial activity loss. The application of amendments has proven effective in enhancing soil nutrients, which significantly affects soil nitrogen and phosphorus cycling process. However, the specific impact of different amendments on the microbial functional potential related to nutrient cycling in saline-alkali soils remains unclear. Hence, metagenomics sequencing was used to investigate soil microbial communities and nitrogen and phosphorus cycling genes in response to different amendments, and to examine the influence of soil physicochemical properties on functional genes in the Hetao irrigation district of China. The results showed that amendments application enriched the Proteobacteria abundance, while inhibiting oligotrophic groups such as Chloroflexi. Compared to the control (CK), the combined application of desulfurization gypsum and cattle manure (DC) notably increased nasA (assimilatory nitrate reduction) and nirB (dissimilatory nitrate reduction), as well as phoD and phoA genes (organic P mineralization). Furthermore, soil AK and AP were primary factors affecting microbial communities and N and P cycling genes. Overall, this study offers valuable insights into soil nitrogen and phosphorus cycling genes and their interactions in response to different amendments, where the application of amendments affects nitrogen and phosphorus cycling by altering soil nutrient availability.