Influence of integrated nitrogen and phosphorus management practices on soil microbial population dynamics

Soil microbial populations are highly responsive to nutrient management practices and play a vital role in nutrient cycling and soil fertility. A field experiment was conducted during two consecutive seasons (2022-23 and 2023-24) to evaluate the influence of integrated nitrogen and phosphorus management practices on soil fungal, bacterial, and actinomycetes populations at different crop growth stages. The experiment was laid out in a factorial randomized block design with six nitrogen management options and three phosphorus management options, replicated thrice. Soil samples were collected at 30 days after transplanting (DAT), 60 DAT, and at harvest, and microbial populations were estimated using standard dilution plate count techniques. Pooled analysis of two years’ data revealed significant variation in microbial populations due to nutrient management practices. Among nitrogen management options, integrated application of organic residues along with bio-consortium and recommended nitrogen dose recorded significantly higher fungal, bacterial, and actinomycetes populations at all growth stages. Microbial populations increased from 30 DAT to 60 DAT and declined slightly at harvest, indicating peak microbial activity during the active vegetative phase. Phosphorus management involving 100 per cent recommended dose applied as basal consistently recorded higher microbial populations compared to reduced phosphorus levels with bio-inoculants. Interaction effects between nitrogen and phosphorus management practices were found to be non-significant. Enhanced microbial populations under integrated nutrient management may be attributed to improved substrate availability, increased organic carbon input, and favorable soil environment for microbial proliferation. The consistency of results across years highlights the sustainability of integrated nutrient management practices. The study concludes that balanced and integrated application of nitrogen and phosphorus is essential for improving soil microbial health and sustaining long-term soil fertility.