Crop coefficient (KC) determination in sprinkler irrigated rice

Experimental trials were carried out in Sardinia in 2002 and 2003, in order to obtain, among other, a first information on kc values at different phenological stages in sprinkler irrigated rice; in 2003 the trials differed for the sowing date. An equipment recording soil moisture content every 10 cm up to 100 cm depth was used to obtain the water balance for the first soil layers. Result analysis highlighted that the layer up to 20 cm covers about 80 % of the crop water requirements for the whole cycle. Kc values were determined as the ratio between crop evapotranspiration and ETo, after Penman-Monteith’s equation. The results show a variability particularly related to the meteorological trend during the trials. Crop coefficient (estimated value) ranged between 0.2 and 0.75 for the initial stage (Kcini),between 0.85 and 1.0 for mid season stage (Kcmid) and was 0.2 for late season (Kcend).