Productivity and Resource Use Efficiency of Potato under Nitrogen Fertigation through Subsurface Drip Irrigation with Mulching

A field experiment was performed at Punjab Agricultural University, Ludhiana, in 2022–23 and 2023–24 to evaluate the effect of subsurface drip irrigation, nitrogen fertigation, and mulching on soil water conservation, water use efficiency, and yield in potato. The experiment was conducted in a randomized block design comprising two drip methods (subsurface drip and surface drip) and eight treatment combinations: T1 (100% ETc + 100% Nitrogen + Mulch @ 6 t ha⁻¹), T2 (100% ETc + 100% Nitrogen + No mulch), T3 (70% ETc + 100% Nitrogen + Mulch @ 6 t ha⁻¹), T4 (70% ETc + 100% Nitrogen + No mulch), T5 (100% ETc + 70% Nitrogen + Mulch @ 6 t ha⁻¹), T6 (100% ETc + 70% Nitrogen + No mulch), T7 (70% ETc + 70% Nitrogen + Mulch @ 6 t ha⁻¹) and T8 (70% ETc + 70% Nitrogen + No mulch), with three replications, while the conventional practice (CP) was maintained for comparison. Results indicated that surface drip irrigation (SDI) performed better in potato as it significantly enhanced growth parameters such as plant height, biomass, relative leaf water content (RLWC), SPAD values, and leaf area index (LAI). Among the treatments, T1 consistently recorded the highest tuber yield, tuber count per plant, haulm yield, and water productivity, and was statistically at par with T5, indicating that a 30% saving in nitrogen was possible under mulching without yield penalty. Compared to conventional practice, all drip fertigation treatments significantly improved tuber yield, nitrogen uptake, and water productivity. Mulching played a crucial role in improving rhizospheric conditions, moisture retention, and nutrient use efficiency, particularly under reduced irrigation (70% ETc). Treatments T3 and T7 recorded significantly higher water productivity and were statistically comparable, highlighting the potential of deficit irrigation under mulching for sustainability.