Conservation agriculture strategies for soil health and carbon restoration in humid subtropical agri-food systems

• Raised Bed Maize–Zero Tillage Lentil–Zero Tillage Green Gram (Sc8) increased soil organic carbon (SOC) to 5.2 g kg⁻¹ and total organic carbon (TOC) to 8.9 g kg⁻¹. • Water-stable aggregates (WSA) improved markedly under Sc8, reaching 35% at 0–15 cm, indicating stronger soil structural stability. • Sc8 enhanced macronutrient availability, recording 227 kg N ha⁻¹, 19.3 kg P₂O₅ ha⁻¹, and 212 kg K₂O ha⁻¹. • Microbial biomass carbon and soil respiration were highest in the RBM–ZtLt–ZtGG system, demonstrating superior biological activity. • Both Sc8 and Sc1 substantially improved soil carbon indices, supporting greater long-term soil resilience. Soil degradation and declining fertility pose serious challenges to agricultural sustainability and agri-food and nutritional security across the Indo-Gangetic Plains, India. This study evaluated eight climate-resilient cropping system scenarios (Sc1–Sc8) integrating cereals, pulses, and oilseeds under conservation agriculture (CA) from 2020–2023. The experimental sites are characterized by deep, fertile alluvial soils classified as Inceptisols (Typic Haplustepts/Typic Eutrudepts) under USDA Soil Taxonomy. The systems involved Oryza sativa L. (rice), Triticum aestivum L. (wheat), Zea mays L. (maize), Lens culinaris Medik. (lentil), Vigna radiata L. (green gram), Brassica juncea L. (mustard), and Sesamum indicum L. (sesame). Post-harvest soil sampling assessed soil organic carbon (SOC), total organic carbon (TOC), carbon indices, nutrient availability, microbial biomass, soil respiration, bulk density (BD), and water-stable aggregates (WSA). Significant differences among scenarios were observed. BD was highest in Sc4 (puddled transplanted rice–zero tillage mustard–green gram) at 1.56 Mg m⁻³, reflecting the compaction effects of puddling. WSA were greatest in Sc8 (raised bed maize–zero tillage lentil–zero tillage green gram) with 35.1% at 0–15 cm. Nutrient availability was also highest in Sc8, recording 227 kg N ha⁻¹, 19.3 kg P₂O₅ ha⁻¹, and 212 kg K₂O ha⁻¹. Micronutrient concentrations (Zn, Fe, Mn, Cu) were significantly elevated in Sc8, surpassing all other scenarios by 12-22%, with biological properties further supporting the superiority of Sc8.Microbial biomass carbon (MBC) and soil respiration (SR) were 18-25% higher compared with Sc1–Sc7. Raised bed maize–zero tillage lentil–zero tillage green gram (Sc8) recorded the maximum SOC (5.2 g kg⁻¹) and TOC (8.9 g kg⁻¹) along with substantial improvements in carbon lability, carbon management index (CMI), pool index (CPI), and recalcitrant carbon fractions. Sc1 (direct-seeded rice–zero tillage wheat–zero tillage green gram) also showed favorable improvements but remained below Sc8. Overall, this study provides novel evidence that integrating raised-bed maize with legumes under zero tillage particularly (Sc8) enhances soil structural stability, carbon sequestration, and biological functioning. The findings strongly support scaling raised-bed and zero-tillage legume-based systems to combat degradation and improve long-term soil resilience and agri-food security in alluvial ecologies of the Indo-Gangetic Plains, India.