Journal of Agronomy and Field Innovations

Background: Soil microbial communities regulate the biogeochemical processes that sustain crop productivity, yet conventional fertilizer-dependent farming progressively erodes their functional capacity. Integrated Nutrient Management (INM), which combines chemical fertilizers with organic manures, compost, biofertilizers, and crop residues, is increasingly promoted as a strategy for restoring soil biological health.
Objective: This study evaluated how different INM treatments influence the abundance and diversity of functional microbial genes governing nitrogen, phosphorus, sulfur, and carbon cycling in agricultural soils, and examined the relationship between microbial functional diversity and soil fertility indicators.
Methods: A field trial was conducted in a Randomized Complete Block Design with five nutrient management treatments, including sole inorganic fertilization, sole organic amendment, and three INM combinations. Soil DNA was extracted, and functional genes (nifH, amoA, nirK, nirS, nosZ, phoD, and carbon-degradation genes) were quantified using quantitative PCR and shotgun metagenomic sequencing on an Illumina platform, followed by bioinformatic annotation against KEGG and functional gene databases.
Results: INM treatments combining organic manure, biofertilizer, and reduced inorganic fertilizer significantly increased the abundance of nifH, amoA, phoD, and nosZ genes relative to sole inorganic fertilization, and raised Shannon and Chao1 diversity indices. Principal coordinate analysis revealed clear separation of microbial functional communities across treatments, and functional gene abundance correlated positively with soil organic carbon, available phosphorus, and microbial biomass carbon.
Conclusion: Integrated Nutrient Management enhances functional gene diversity and nutrient-cycling potential of agricultural soils more effectively than either chemical or organic inputs alone, supporting its adoption as a biologically sound pathway toward sustainable and climate-resilient crop production.