Estimating of crop coefficient from water consumption in Manihot esculenta Crantz of cv. Kasetsart 50

ABSTRACT One of the values that is required to manage irrigation of crops efficiently is crop coefficient (Kc). Kc is the coefficient for growing crops to reach full potential under the optimum condition for fertility and water in soil. Kc is already known to be species and cultivar specific. The objective of this research was to use the adapted version of the lysimeter method with indirect measurement of water consumption for Kc estimation in Kasetsart 50 (Manihot esculenta Crantz of cv. KU50) at the 3 distinct growth stages; in the initial stage (0 – 90 DAP), middle stage (91 - 150 DAP) and end stage (151 - 180 DAP) of the growth cycle. The experiment plot was designed the tank using sealed cement block as the basal structure, amount of water applying in drip irrigation was determined by soil moisture sensors in 30 cm and 60 cm from soil surface and dripping rate. The results showed the average Kc value generated for the different growth stages were: 0.6696_Init which was gradually increased to 1.6576_Mid in middle stage and slightly decreased at the end of middle stage and then Kc was sharply decreased to 0.7927_end in end stage. The estimation of Kc values of KU50 were higher compared to FAO Penman-Monteith in all 3 growth stages, but this research could report the first specific value of Kc in the Thai variety of cassava.