Conservation agriculture induced changes in soil dehydrogenase activity under a rice- chickpea cropping system

Conservation agriculture (CA) is a sustainable soil management approach that improves soil biological functioning and ecosystem resilience. Soil dehydrogenase activity (DHA) is a sensitive indicator of microbial activity and soil biological health. The present study was conducted to assess the effect of different conservation agriculture practices on soil DHA in a rice–chickpea cropping system. Five tillage and residue management practices involving combinations of transplanted/direct-seeded rice, zero/conventional tillage and residue retention were evaluated. Soil DHA was determined at initial, flowering and harvest stages of both crops using the 2,3,5-2,3,5-triphenyl tetrazolium chloride (TTC) reduction method. Significant differences in DHA were observed among conservation agriculture treatments during both rice and chickpea phases. The highest DHA was consistently recorded under zero-till direct-seeded rice followed by zero-till chickpea with 20 cm standing stubble retention (T₃), whereas the lowest activity was observed under conventional tillage without residue retention. During the rice phase, T₃ recorded mean DHA values of 40.88, 57.26 and 49.45 µg TPF g⁻¹ dry soil h⁻¹ at the initial, flowering and harvest stages, respectively. Similarly, during the chickpea phase, T₃ recorded the highest DHA values of 40.15, 66.76 and 57.04 µg TPF g⁻¹ dry soil h⁻¹ at the respective growth stages. Dehydrogenase activity increased up to flowering and declined slightly at harvest, reflecting the influence of crop growth dynamics on microbial activity. The enhanced DHA under zero tillage with residue retention may be attributed to improved organic matter availability, reduced soil disturbance and favourable microbial habitats. The study highlights that conservation agriculture, particularly zero tillage combined with residue retention, improves soil biological activity and contributes to sustainable soil health management in the rice–chickpea cropping system.