MAXIMUM EVAPOTRANSPIRATION AND CROP COEFFICIENT IN THE GROWTH STAGES OF IRRIGATED WATERMELON

摘要

This experiment was conducted during the period of October to December of 1997 at the Hydraulic and Irrigation Laboratory of the Agricultural Engineering Department - University of Fortaleza, Fortaleza, CE. The evapotranspiration and crop coefficient (kc) of watermelon (cv Crimson Sweet) was estimated at different development stages. The crop coefficient was obtained calculating the relation of the maximum evapotranspiration (ETm) estimated by the soil water balance and the reference evapotranspiration estimated by the methods: Penman - Monteith, Radiation FAO - 24 and Blaney Criddle FAO - 24. The results indicated that the ETm increased until 45 days after planting when the crop reached the stage of fruit filling and varied from 2.2 mm day-1 at initial to 8.7 mm day-1 at the stage of fruit filling. The mean values of kc at different stages were higher than the FAO at the flowering, filling and maturation stages and were lower than the FAO during initial and development of branches. The total evapotranspiration after 59 days was 319.6 mm.