Impact of Diverse Rice-based Cropping Systems on Soil Microbial Count and Enzyme Activities in the Western Coastal Plains of India

Abstract

Soil biological degradation in rice monoculture necessitates diversification strategies, yet the persistence of microbial populations and their activities remain unclear. The study was undertaken in the western coastal plains of southern Kerala to assess the impact of diverse rice-based cropping systems on soil biology. Soil enzymes, viz., dehydrogenase, urease, and acid phosphatase and microbial population across three seasons in ten diverse rice-based cropping sequences were assessed. Legume-integrated systems meant for soil health (T3: Rice–Bush cowpea–Groundnut + Dhaincha; T4: Rice + Dhaincha–Rice + Dhaincha–Redgram + Groundnut) and vegetable-diversified rotation meant for income enhancement (T9: Rice–Sweet potato–Cucumber) achieved the highest dehydrogenase activSities of 123.09, 118.93, and 124.00 μg TPF g⁻¹ 24h⁻¹, representing an 88% increase over rice-fallow control. Urease peaked at 102.05 and 100.10 mg urea g⁻¹ soil h⁻¹ in T3 and T9 with 45% enhancement against control, while acid phosphatase reached 38.18–38.77 μg PNP g⁻¹ h⁻¹ with 34–36% increase. Total microbial count increased 30–34% in diversified systems in a range of 19.11–19.79 log CFU g⁻¹ against the control (14.75 log CFU g⁻¹) with bacteria (36% increase) and actinomycetes (35% increase) responding significantly while fungi remained invariant. T3 (Rice– Bush cowpea– Groundnut + Dhaincha) is optimal, achieving highest microbial counts (19.79 log CFU g⁻¹) and peak enzymatic activities through synergistic legume integration and green manure incorporation.