Dual crop coefficient for the early-cycle soybean cultivar SoyTech 815 RR

ABSTRACT The objective of this study was to determine the dual crop coefficient of an early-cycle soybean cultivar for the city of Tangará da Serra, MT, Brazil, using high-precision lysimeters. The method used was the dual crop coefficient (dual Kc) of FAO Bulletin 56, constitued by soil evaporation coefficient (Ke), determined by microlysimeters, and by basal crop coefficient (Kcb), determined by weighing lysimeters. Reference evapotranspiration (ETo) was calculated using the Penman-Monteith equation. Soybean sowing and harvesting were performed in the 2015/16 season with spacing of 0.45 m between rows. The reference evapotranspiration (ETo) estimated for the cultivation period was 267.06 mm; the crop evapotranspiration was 323.61 mm throughout its cycle. The Kcb values determined by lysimeters for soybean cultivation were 0.47, 1.15 and 0.89 for the initial, intermediate and final stages, respectively; Ke values at the initial, intermediate and final stages were 0.94, 0.14 and 0.44, respectively.