Plastic mulching consistently improves brinjal performance, but drip irrigation benefits are soil dependent: A two-location field study

Brinjal (Solanum melongena L.) requires considerable soil moisture throughout its life cycle, therefore, its cultivation in water constraint area is difficult. Though different soil moisture conservation technologies and lower water use irrigation systems have been developed for crop cultivation, their successful deployment largely depends on the locality, especially on soil characteristics. This study evaluated the effects of irrigation regimes, mulching practices, and their combination on growth, stress physiology and irrigation water use efficiency (IWUE) of brinjal across two field locations with contrasting soil conditions. Location 1 had coarser soil, lower nutrient and organic matter content profiles and lower water-holding capacity than location 2. The experiment comprised three irrigation levels [rainfed (I0), conventional furrow irrigation (IC), and drip irrigation (ID)] and three mulching treatments [no mulch (M0), straw mulch (MS), and plastic mulch (MP)] with three replications at both locations. Irrigation and mulching both significantly influenced growth, stress indicators, fruit yield, and IWUE, though the effects of the treatment on these parameters varied between locations. At Location 1, drip irrigation (ID) produced a fruit yield of 8.90 ± 5.68 t ha-1, with considerable variability among replicates, and did not differ significantly (p = 0.88) from conventional furrow irrigation (IC) or the rainfed treatment (I0). In contrast, at location 2, drip irrigation outperformed (21.88 ± 9.44 t ha-1) other treatments, being 117% and 32% higher than I0 and IC, respectively. Plastic mulching (MP) improved growth, reduced drought stress and increased yield compared to MS and M0 at both locations. The highest yield at location 1 (23.18 ± 6.62 t ha-1) occurred under IC × MP, while the highest yield at location 2 (32.93 ± 1.62 t ha-1) was achieved under ID × MP. IWUE peaked at 38.84 kg ha-1 mm-1 (IC × MP) in location 1 and 65.87 kg ha-1 mm-1 (ID × MP) in location 2. A linear mixed model estimated that plastic mulch increased yield by ~10.63 t ha-1 (95% CI: 6.58-14.68 t ha-1, p < 0.001) over no mulch, and IC × MP produced a synergistic yield gain of 11.03 t ha-1 (95% CI: 5.3-16.76 t ha-1, p = 0.003) over the control. Overall, plastic mulching consistently enhanced brinjal performance, while the benefit of drip irrigation was soil-dependent and was most evident in the higher water-retention field.