Determination of crop coefficient (Kc) of sago palm (metroxylon sagu) on several growth stages

Sago palm productivity and quality of wetland sago starch are still relatively low. Rainfed dryland is sufficient potential for sago palm development if plant water needs are met. Crop coefficients are important in predicting crop water requirements. The determination of crop coefficients was carried out on three stages of sago plant growth (initial-stage, mid-stage, and end-stage). The estimation of standard evapotranspiration is conducted using the Penman-Monteith method with the Cropwat 8.0 application. The estimation of sago palm evapotranspiration utilizes the lysimeter method on the initial-stage and plot observation in the mid-stage and end-stage. The determination of the crop evapotranspiration adheres to the water balance principle. Crop coefficient values are obtained by comparing standard evapotranspiration with the crop evapotranspiration. The results obtained are standard evapotranspiration at the study site 3.91 mm/day. Sago palm evapotranspiration is different in each growth phase (initial stage of about 2.44 mm/day, mid-stage of about 2.91 mm/day, and end-stage of about 3.82 mm/day. The crop coefficient of sago palm in the initial stage of growth that is 0.62, the mid-stage is 0.77 and the end-stage of growth is 0.98. The Kc value is used to predict the water needs of sago palm if they are to be developed in rainfed dryland areas.