Long-term effects of reduced tillage and legume-based diversification on productivity, soil carbon storage and resource-use efficiency in rainfed agroecosystems

Rainfed agroecosystems in north-western India are constrained by low soil organic carbon, weak soil structure, and highly variable rainfall, resulting in unstable productivity and inefficient resource use. Long-term integration of tillage practices with diversified cropping systems remains limited, particularly in the rainfed Kandi foothill region of Punjab. A five-year field experiment (2021–22–2025–26) was conducted using a split-plot design with three replications to evaluate two tillage systems (conventional tillage and reduced tillage) and six cropping systems (maize–wheat, maize–Indian mustard, maize–chickpea, groundnut–wheat, groundnut–Indian mustard, and groundnut–chickpea). Crop productivity, soil properties, soil organic carbon (SOC), rainwater-use efficiency (RWUE), energy-use efficiency, and economic returns were assessed. Reduced tillage increased maize equivalent yield (MEY) by 4.9–6.0% compared with conventional tillage across cropping systems, with the highest MEY (11.74 t ha⁻¹) under reduced tillage–groundnut–chickpea, which was 48.2% higher than that under conventional tillage–maize–wheat (7.92 t ha⁻¹). Reduced tillage–groundnut–wheat recorded the highest pooled net return (₹158,477 ha⁻¹), benefit–cost ratio (3.44), energy-use efficiency (17.3), and energy output (301,800 MJ ha⁻¹). Reduced tillage decreased soil bulk density to 1.31–1.36 Mg m⁻³ and increased porosity to 46.5–49.0% and infiltration rate to 10.2–12.1 mm h⁻¹ . SOC stock increased from 7.30 Mg C ha⁻¹ initially to 9.60 Mg C ha⁻¹ under conventional tillage and 10.97 Mg C ha⁻¹ under reduced tillage, representing relative increases of 31.5% and 50.3%, respectively; reduced tillage increased SOC stock by 14.3% compared with conventional tillage. RWUE was significantly affected by tillage, cropping system, and their interaction (P < 0.01, P < 0.01, and P < 0.05, respectively). Therefore, reduced tillage combined with diversified, legume-based cropping systems, particularly groundnut–chickpea and groundnut–wheat, improved system productivity, profitability, energy-use efficiency, and soil quality, demonstrating its potential as a sustainable management strategy for rainfed Kandi agroecosystems of Punjab.