Sugar cane crop coefficient by the soil water balance method

Current assay, conducted on the experimental farm of the Goias Federal Institute, campus at Urutai GO Brazil, determines the crop coefficient (Kc) for sugar cane in the Brazilian savannah at several phases of development. Kc was determined by the soil water balance method in a 3.0 m3 suspended drainage lysimeter, measuring 1.0 m in width and height and 3.0 m in length. Reference evapotranspiration (ET0) was determined by Penman-Piche’s equation with data on air evaporating capacity with Piche’s evaporimeter. Crop evapotranspiration (ETc) was performed by the amount of water available at the bottom of the lysimeter. Irrigation occurred when water capacity on the soil reached -100 KPa, by employing drip subsurface irrigation system. Coefficients of sugar cane crop at different phases were 0.31 (initial), 1.15 (crop development), 1.25 (mid-season) and 0.90 (late season). Crop coefficient values were similar to the suggested by FAO-33.   Key words: Saccharum officinarum L., drainage lysimeter, drip subsurface irrigation, evapotranspiration of crops.