Evaluation of crop coefficients for Rabi Sorghum (Sorghum bicolar monech) in semi-arid climate

Abstract

Planning and strategic management of irrigation water are the key elements for successful crop production. In this study, evaluation of crop coefficients (K C ) on daily and seasonal basis was accomplished for rabi (winter or post rainy) sorghum in semi-arid climatic conditions of India. The crop coefficients for sorghum were developed using lysimetric measured actual crop evapotranspiration (ET C ) and reference evapotranspiration (ET O ) based on the FAO 56 Penman Monteith Method (FP-M). The developed K C values for sorghum during initial, crop development, mid-season, late season stages and at harvest were 0.65, 0.60, 0.50, 0.24, and 0.14, respectively. The results indicated that the actual K C values were considerably different and lower than those suggested by FAO indicating the need for developing these values at the local scale. The measured K C in initial stage was higher than that of empirical K C suggested in FAO 56 whereas K C at development (pre-flowering) stage is in close conformity with that of FAO empirical K C when sufficient moisture was present in the soil. However, the unusual decreasing trend of measured K C from 55 days after sowing of crop at flowering and grain formation stage strongly pointed towards the need of at least two protective irrigations for successful sorghum crop production if grown under rainfed situations.