Impact of Long-Term Integrated Nutrient Management Practices on Soil Bacterial Diversity: A 16S rRNA-Based Metagenomic Approach

Abstract

The growing worlds population, expected to surpass 9 billion by 2050, demands a 70-100% increase in farm productivity, posing significant challenges for sustainable agriculture. Conventional farming, reliant on chemical fertilizers and pesticides, negatively impacts environmental sustainability and food quality. Metagenomics, a culture-independent technique, has revolutionized the study of microbial communities by enabling comprehensive analysis of microbial diversity and function. This study evaluated the effects of combined nutrient management practices--including farmyard manure (FYM), wheat straw, green manure, and NPK fertilizers--on soil bacterial diversity using 16S rRNA-based metagenomic analysis. Key findings revealed the dominance of bacterial phyla such as Proteobacteria, Actinobacteria, and Firmicutes, which play critical roles in nutrient cycling, organic matter decomposition, and plant growth promotion. Distinct taxonomic distributions were observed across the samples, with Proteobacteria and Firmicutes dominating in control (T1), NPK (T2), and NPK_Green Manure (T5) treatments, while a shift in phyla composition was noted in NPK_FYM (T3) and NPK_WheatStraw (T4). Genus-level analysis revealed that Pseudomonas and Bacillus species were abundant in control (T1) and NPK (T2), while Sphingomonas species were dominant in NPK_FYM (T3). Further diversity analyses revealed significant variation across the samples, with T3 showing the highest richness and control (T1) showing the lowest richness. The rarefaction curve confirmed sufficient sampling for capturing microbial diversity, while beta diversity analysis, including Principal Coordinate Analysis (PCA) and Bray-Curtis clustering, indicated distinct microbial community structures across different treatments. The combined use of organic amendments with NPK fertilizer enhanced microbial diversity and population, indicating their potential to support resilient and productive soil ecosystems.