Assessment of evapotranspiration, water productivity and yield response factor for groundnut under deficit irrigation using lysimeter in a hot arid ecosystem

In this study, we focused on precise determination of actual crop evapotranspiration (ETc) of groundnut in an arid region of India using single load cell-based mini-lysimeters. This study, for the first time, integrated two water saving techniques, i.e., pressurized irrigation system through mini-sprinklers and deficit irrigation strategy. The groundnut crop (var. Girnar-2) was grown in lysimeter as well as in field plots under deficit irrigation treatments based on cumulative pan evaporation (CPE), i.e., T₁ (100% of CPE), T₂ (80% of CPE), T₃ (60% of CPE) and T₄ (40% of CPE) with three replications during 2014-2018. Lysimeters’ weights were monitored daily to determine ET_c and soil moisture at weekly interval. Yield response factor (K_y) and crop water productivity were computed in all four treatments. The ET_c (661-817 mm) and pod yield (4.2 t ha^-1) for groundnut were obtained as the highest in treatment T₁. However, water productivity was maximum (0.61 kg m^-3) in treatment T₂ on sacrificing 8.7% of the yield obtained in treatment T₁. The mean Ky value for groundnut under deficit irrigation was computed as 0.63 and varied from 0.68 (T₂) to 1.34 (T₄). This finding indicates that groundnut can tolerate up to 80% deficit irrigation, and beyond this level, the crop becomes sensitive to water stress with large reduction in pod yield. On the other hand, the pod yield revealed 24% and 46% reductions at 60% and 40% deficit irrigation levels, respectively. Therefore, in arid climate, where water is a precious and limited natural resource, irrigation at 80% CPE in groundnut crop is plausible and profitable irrigation water management strategy.