Vol. 7, Issue 11, Part A (2025)

Soil salinization and sodification severely constrain agricultural productivity, particularly in irrigated vertisols of semi-arid regions. Subsurface drainage systems are widely adopted for reclamation of sodic soils, but drain spacing strongly influences nitrate (NO₃⁻) leaching, posing risks to nitrogen (N) use efficiency and water quality. A field experiment was conducted during 2024-25 at Agricultural Research Station, Kasbe Digraj, Sangli, Maharashtra, India to quantify the temporal variability of nitrate leaching under different drain spacings in adsali sugarcane (Saccharum officinarum L.) grown on sodic vertisol. The SSDS was installed at 120 cm depth with lateral spacings of 15, 25, and 40 m, along with a control (no drainage). Drainflow samples were collected after rainfall and irrigation events, and analyzed for NO₃⁻ concentration. Results showed that adsali sugarcane utilized 314.92 lakh L ha⁻¹ water annually, of which 63.38% was discharged through drainage. Mean NO₃⁻ concentrations in drainflow water varied significantly with drain spacing, ranging from 5.96 mg L⁻¹ (15 m) to 3.83 mg L⁻¹ (40 m), compared with 7.13 mg L⁻¹ in control. Annual NO₃-N losses were highest under 15 m spacing (113.33 kg ha⁻¹) and lowest under 40 m spacing (73.63 kg ha⁻¹). Temporal peaks in nitrate leaching coincided with fertilizer application (January-February), whereas minimum losses occurred during monsoon months. Overall, the 40 m drain spacing significantly reduced nitrate leaching without impairing drainage function. These findings suggest that optimized Sub surface drainage system design can enhance nitrogen use efficiency while mitigating environmental risks in sodic vertisols.