Input-intensive cereal systems in the north-western Indo-Gangetic Plains face declining nitrogen use efficiency (NUE) and soil health. We evaluated whether conservation agriculture (CA)—minimal soil disturbance with surface residue retention—combined with subsurface N placement can improve maize performance compared to conventional tillage (CT). A long-term trial initiated in 2008 with CA and CT systems was restructured in 2021 into a split-plot experiment for maize, with N subplots (100, 125, and 150 kg N ha -1 ) evaluated over three seasons (2021–2023). Farmers’ practice (FP: CT + residue removal + surface-broadcast N) and two zero-N controls were newly introduced in 2021 as additional benchmark treatments for comparison. The CA consistently enhanced canopy development, phasic biomass, and final yield versus CT and FP. Pooled grain yield was highest under zero-till and permanent beds (6118 kg ha -1 ), exceeding CT (5400 kg ha -1 ) and FP (5265 kg ha -1 ). The 125 kg N ha -1 produced yields comparable to 150 kg N ha -1 in CA, while additional biomass at 150 kg N ha -1 accrued largely as stover. Nitrogen uptake and efficiency were superior under CA (zero-till: 146 kg N ha -1 uptake), with NUEs peaking at 125 kg N ha -1 . CA enriched and stabilized mineral N in surface and near-surface layers, and improved soil water content across 0–30 cm. Net returns and benefit–cost ratios were highest under CA, with zero-till at 125 kg N ha -1 achieving returns comparable to 150 kg N ha -1 but with lower input cost. Overall, mature CA with residue retention and subsurface N placement delivers a yield–N efficiency–profitability “ win–win ” for maize in this region; 125 kg N ha -1 is an agronomic and economic optimum under CA. • Long-term CA with residue retention outperformed CT and FP for maize productivity. • Zero tillage and permanent beds improved yield, NUE, SOC, and water retention. • Moderate N input (125 kg ha -1 ) matched higher rates under CA with lower cost. • CA enriched surface mineral N and nearly doubled topsoil SOC from 2008 baseline. • ZT-N125 delivered the best yield–N efficiency–profitability synergy.
Patra et al. (Sun,) studied this question.