Yield, evapotranspiration and water productivity of rice (Oryza sativa L.)–wheat (Triticum aestivum L.) system in Punjab (India) as influenced by transplanting date of rice and weather parameters

Rice–wheat cropping system being highly productive and profitable, dominates the irrigated alluvial tract of Indo-Gangetic Plain of South Asia. In this region, the transplanting is staggered over a longer period (starting from early May to end of June) due to scarcity of migratory labour and power supply. Yield response of rice to different transplanting dates gets varied with weather conditions at different growth stages of the crop as well as with the occurrence of insect-pests infestation. The present investigation, therefore, concerns the effects of different dates of transplanting and weather parameters on yield, evapotranspiration and water productivity of rice and subsequent wheat in rice–wheat cropping system in Indian Punjab involving field experimentation for 2 years and simulation for 23 years. For the simulation study, crop production and management (CROPMAN) model which is a multi-year, multi-crop and daily time step cropping system was used. The simulated rice yields with varying dates of transplanting of rice complimented the field results and showed an increasing trend when transplanting was shifted from high to low evaporative demand owing to favourable weather conditions for plant growth. Duration of temperature greater than 37 °C during post-transplanted seedling period (DsT), temperature greater than 33 °C (TF) and number of rain showers (NSF) from flowering to pollen stage (75–90 days after transplanting) affected rice yield (Yr) significantly. Sixty-seven percent variability in rice yield was explained by these weather parameters following the equation Yr = 0.656SR − 36.9DsT − 175.9TF − 102.5NSF + 11995. Shifting of transplanting dates also resulted into a saving of 192 mm as wet (evapotranspiration) and 590 mm as dry (irrigation) water. Real and apparent crop water productivities (grain yield per unit of water consumed by the crop as ET and irrigation water applied, respectively) were more (>70%) in rice transplanted under lower (end of June onwards) than higher evaporative demand (mid May).