Influence of Soil Coverage on Evapotranspiration and Dual Crop Coefficients on Soybean

Abstract

Crop coefficient (Kc) study is the main tool used to determine the plant water consumption enabling irrigation management. The dual Kc is related to the evaporation coefficient of water from the soil (Ke), therefore, the objective of the work was to evaluate the influence of the soil coverage, in the variability of the crop evapotranspiration (ETc) of soybean and the dual Kc. The Kc values were determined by the ratio between ETc and ETo (reference evapotranspiration). ETo was estimated using the methodology proposed by Penman-Monteith FAO-56. The ETc values were obtained by the water input and output ratio of the weighing lysimeters system for the culture development phases established as initial; development; intermediate and final. The culture presented a cycle of 118 days for both treatments; the volume of the water precipitated and supplied by irrigation was 786.4 and 89 mm, respectively. The water consumption determined by ETc during the crop cycle was 699.10; 672.57; 649.06; 724.02; 643.46 and 638.12 mm, respectively for levels 0; 2; 4; 6; 8 and 10 t ha-1 of the dry mass of Brachiaria. The average dual Kc obtained was 1.60; 1.48; 1.40; 1.53; 1.42 and 1.47, respectively for coverings and a reduction in Kc was observed for treatments with soil coverage. Yield and development of the root system, were increase on soil coverage of 2 and 4 t  ha-1.