Crop coefficient, reference crop evapotranspiration and water demand of dry‐season Boro rice as affected by climate variability: A case study from northeast Bangladesh

Abstract

AbstractClimate variability and change significantly influence crop water demand by affecting crop coefficient (Kc), reference crop evapotranspiration (ETo, a grass reference) and potential crop evapotranspiration (ETc). The climatic effects on these hydroclimatic parameters were investigated in the past mostly for the entire crop growth period, but little or no information is available on their variation over different growth stages of the crops, specifically in Bangladesh. Therefore, this study intended to evaluate the climatic effects on these hydroclimatic parameters at the initial, development, mid‐season and late‐season growth stages of two rice varieties (Bangladesh Rice Research Institute [BRRI] dhan28 and BRRI dhan29) dominantly grown in the dry season in two northeast districts/subdistricts (Sylhet and Srimongal) as well as many other districts of Bangladesh. Kc, ET0 and ETc were analysed for the period from 1994 to 2015 using the analytical approach of the Food and Agriculture Organization (FAO) Penman–Monteith method. The results revealed that the Kc of the rice varieties increased in all growth stages over time, with the maximum Kc (1.247) in the mid‐season stage in Srimongal. ETo and ETc were found to be maximum in the mid‐season and late‐season stages, respectively. The potential crop water demand (CWRpot) greatly varied among the initial and development stages and between the two rice varieties. The initial and mid‐season growth stages of rice required more water than the other growth stages. The results on the growth stage‐wise variation of the hydroclimatic parameters pertinent to rice cultivation may greatly contribute to irrigation scheduling for dry‐season rice cultivation and planning water resources in the study region.