Yield features of two soybean varieties under different water supplies and field conditions

The aim of the study was to quantify the impact of water stress, based on crop water stress index on the yield and yield components in two soybean (Glycine max L.) varieties Sinara and Sigalia with distinct water demand. Three water levels were imposed during 2017 and 2018 growing seasons: 1) the unlimited in traditional evapotranspirometers, 2) the halved evapotranspiration during flowering and 3) the rainfed. LAI was recorded at weekly intervals. Total aboveground biomass, seed yield, 1000-grain weight, oil and protein contents were measured at harvest. Irrespective of water supply, the water stress tolerant Sinara had greater seed yield due to increased LAI, dry matter and 1000-grain weight compared to Sigalia that may be advantageous to obtain stable yield under variable weather conditions. The relationship between water stress index and seed yield (R-2 = 0.744) was best described by polynomial function; as the evapotranspiration increased, the water stress index in line with crop temperatures, T, and its SD values decreased. Linear relationship between water stress index and water use efficiency exhibited that each 0.1 increase in water stress index above 0.2 would improve the soybean water use efficiency by 0.49 +/- 0.13 kg m(-3). This information could particularly be useful for farmers cultivating the soybean on water scarce areas.