Long-term effects of organic and inorganic inputs on soil microbial populations in Maharashtra, India

Abstract

Long-term nutrient management practices play a crucial role in regulating soil biological health and sustainability of cropping systems. The present study evaluated the influence of long-term application of organic and inorganic nutrient inputs on soil microbial populations in two long-term fertilizer experiments located at Rahuri and Solapur, Maharashtra, India. The experiments represented contrasting cropping systems, namely soybean-wheat at Rahuri and rabi sorghum at Solapur, with treatments involving sole inorganic fertilizers, organic nutrient sources, and their integrated use. Soil samples collected from the surface layer (0-15 cm) were analyzed for bacterial, fungal, and actinomycetes populations using the serial dilution and plate count method. Results indicated a significant improvement in microbial populations under integrated nutrient management practices compared to sole inorganic fertilizer application and control treatments at both locations. Among the organic sources, farmyard manure either alone or in combination with inorganic nitrogen recorded the highest populations of bacteria, fungi, and actinomycetes, followed by crop residues, green manure, and Leucaena loppings. Sole application of inorganic fertilizers improved microbial populations over the control but was markedly inferior to integrated treatments. Overall, the study highlights that long-term integration of organic inputs with recommended fertilizer doses is essential for sustaining soil microbial activity and enhancing soil health in major cropping systems of Maharashtra.