Vol. 9, Special Issue 12, Part V (2025)

Soil biological indicators respond rapidly to changes in tillage, residue management, and nitrogen (N) availability, making them sensitive markers of soil health in conservation agriculture (CA). A two-year field experiment (2021-22 and 2022-23) was conducted in the Indo-Gangetic Plains of India to evaluate the effects of conservation agricultural practices (CAP) and nitrogen management practices (NMP) on soil biological properties in a wheat-greengram-maize cropping system. The experiment was laid out in a split-plot design with three CAP treatments—conventional tillage (CT), zero tillage with residue retention (ZT+R), and permanently raised beds with residue retention (PB+R)—as main plots, and seven NMP treatments (N₁-N₇) as subplots. Soil microbial biomass carbon (MBC), fluorescein diacetate hydrolytic activity (FDA), and dehydrogenase activity (DHA) were measured at the key growth stages of all three crops.

Across crops and stages, CAP exerted a dominant influence on soil biological activity, with PB+R consistently recording the highest MBC, FDA, and DHA, followed by ZT+R and CT treatments. Relative to CT, PB+R increased the pooled MBC by 4-7%, FDA activity by 6-9%, and DHA by 9-15%, indicating improved microbial habitat, substrate availability, and metabolic activity under residue-retained systems. The effects of nitrogen management were comparatively smaller; optimized N treatments (N₂ and N₅) showed marginal but significant improvements in biological indicators compared to reduced-N and control treatments. The interaction effects between CAP and NMP were mostly non-significant. The results demonstrated that residue-retained conservation agriculture, particularly permanent raised beds, is the primary driver of soil biological health in cereal-legume-cereal rotations, whereas optimized nitrogen management supports but does not substitute the residue-mediated biological benefits.