Lysimeter based crop coefficients for estimation of crop evapotranspiration of black gram (Vigna Mungo L.) in sub-humid region

Black gram is dominant pulse crop of the region. ?Crop coefficient is an important parameter, which needs to be determined for accurate estimates of the crop water requirement. ?Crop coefficient, the ratio of potential crop evapotranspiration to reference evapotranspiration, is an important parameter in irrigation planning and management. ?However, this information is not available for many important crops in the study region. ?A study was undertaken to develop crop coefficients for black gram crop, and a comparison is made of single and dual crop coefficient approaches to estimate actual crop evapotranspiration under the climatic conditions of Udaipur, India. ?Crop coefficient was developed from daily measured black gram evapotranspiration (ETBG) data by electronic weighing lysimeter and reference evapotranspiration calculated using standard Penman-Monteith method. ?The measured values of crop coefficient for the crop were 0.48, 1.18 and 0.33 during initial, mid-season and late-season stages. ?The evaluation of different approaches showed that daily ETBG estimate based on dual crop coefficient method have been found best (SE=0.40, r=0.96).? Furthermore, a quadratic curve (second-order polynomial) method were fitted well (SE=0.47, r=0.94) to predict crop coefficient values as function of days after sowing (DAS).? These locally developed and evaluated values can be used for proper irrigation planning in water scarcity area of Udaipur and other areas with similar agro-ecological conditions.