Conservation agriculture practices impact on biological and microbial diversity in earthworm cast under maize-wheat system

Soil degradation is a major global concern due to its negative impact on soil quality and the sustainability of agricultural resources. The conservation agriculture (CA) approach, which includes three key principles such as zero tillage, retention of crop residue and crop rotation has gained widespread adoption to help mitigate the climate change effects on agricultural soils and meet the growing demand for increased production. Earthworm communities, along with microbial activity and diversity, are highly sensitive to tillage practices. Additionally, microbial activity and diversity quickly respond to different cropping systems, making them effective indicators for detecting short-term changes in soil functioning. We therefore, assess the effects of CA innovative approached after 6-years on biological and microbial diversity within earthworm cast in maize-wheat system (MWS). The treatments consist of PBM-RN₀/ZTW-RN₀ (permanent beds No-N control-both residues removed and wheat with zero tillage); PBM+RN₀/ZTW+RN₀ (permanent beds No-N control-both residues retained)-50% of maize stover and 25% of wheat residue retained; PBM-RN₁₂₀/ZTW- RN₁₂₀ (permanent beds with 120 kg N ha^-1 both residues removed wheat with zero tillage); PBM+RN₁₂₀/ZTW+RN₁₂₀ (permanent beds with 120 kg N ha^-1 both residues retained and wheat with zero tillage) and FBM-RN₁₂₀/CTW-RN₁₂₀ (fresh beds in maize/CT in wheat with 120 kg N ha^-1 both residues removed). The result of present study showed that activities of carbon (C) cycle-related enzymes in the cast soils viz., dehydrogenase (DHA), β-glucosidase (β-glu), cellulase, and xylanase were significantly higher under PBM+RN₁₂₀/ ZTW+RN₁₂₀ than under PBM-RN₀/ZTW-RN₀. Specifically, the activities of these enzymes were 21.5, 26.8, and 76.5% higher under the PBM+RN₁₂₀/ZTW+RN₁₂₀ treatment, respectively. Moreover, the Alk-P activity was found to be 1.3 times higher in the PBM+RN₁₂₀/ZTW+RN₁₂₀ treatment than in the PBM-RN₀/ZTW-RN₀ treatment. The bacterial, fungal, and actinomycete counts in the cast soil ranged from 6.87 to 7.47 CFU (colony forming units) x 10⁶ g^-1 soil, 3.87–3.30 CFU x 10⁴ g^-1 soil, and 5.09–5.67 CFU x 10⁴ g^-1 soil, respectively. Total organic carbon (TOC) showed significant increases of 34.6% under PBM+RN₁₂₀/ZTW+RN₁₂₀ as compared to PBM-RN₀/ZTW-RN₀. The less labile C (Frac. 3), total carbohydrate carbon (TCHO), phenol oxidase (PHE) and peroxidase (PER) were observed as the sensitive indicators under different tillage, rate of nitrogen and residue management practices. This study suggests that permanent beds with crop residue retention with balance fertilization practices can be recommended and popularized to the overall improvement of soil biological pools within earthworm casts in MWS.