Influence of subsurface drip lateral depth and irrigation-nitrogen fertigation regimes on growth and productivity of high-density planting system cotton

Water scarcity necessitates the adoption of advanced irrigation technologies such as subsurface drip irrigation (SSDI) to enhance cotton productivity under the high-density planting system (HDPS). A field experiment was conducted at Tamil Nadu Agricultural University, Coimbatore, during the summer 2025 and winter 2025–26 seasons to optimise subsurface drip irrigation lateral depth and nitrogen fertigation for HDPS cotton. The experiment was laid out in a strip plot design with four lateral placement depths (0, 10 ± 2, 20 ± 2 and 30 ± 2 cm) and four irrigation-nitrogen fertigation combinations, replicated 3 times. Subsurface lateral placement at 30 ± 2 cm recorded the highest seed cotton yield of 2704.25 and 2790.55 kg ha-1 during the summer and winter seasons, respectively. Likewise, irrigation at 1.0 crop evapotranspiration (ETc) combined with 100 kg nitrogen (N) ha-1 produced the highest yields of 2615.55 and 2665.87 kg ha-1. The combination of 30 ± 2 cm lateral placement, 1.0 ETc irrigation and 100 kg N ha-1 fertigation increased seed cotton yield by 39.5 % in summer and 47.3 % in winter compared with surface lateral placement (0 cm) receiving 0.75 ETc + 75 kg N ha-1. Therefore, subsurface lateral placement at 30 ± 2 cm with irrigation at 1.0 or 0.75 ETc and 100 kg N ha-1 can be recorded superior growth, yield attributes and productivity of HDPS cotton under subsurface drip irrigation conditions.