Crop-water relation and production of two soybean varieties under different water supplies

The estimation of evapotranspiration in a canopy rather than at the plant level is of interest to crop scientists. Information about the plant-water relationship at the canopy level permits better irrigation-related estimates. In addition, there is very limited proper instrumentation to measure evapotranspiration in water-stressed crops in trials under field conditions. The aim of this study was to estimate the evapotranspiration rates, canopy temperatures, T-c, crop water stress index (CWSI), and production of two soybean varieties using three water supply levels (unlimited water, 50% of water requirement in evapotranspirometers, and rainfed conditions). To date, there are no studies that have attempted to estimate the amount of water loss in stressed field-grown crops while operating converted evapotranspirometers. For each 0.1 increase in CWSI above 0.2, seed yield decreased by 434.1 +/- 28.8gm(-2). Mean CWSI and T-c data were inversely related to crop water use efficiency (WUE). WUE and CWSI showed a quadratic relationship, and the economic limit of CWSI was 0.62. T-c and CWSI could serve as indicators for selecting soybean varieties with different levels of stress tolerance. However, due to the short observation period in this study, results might be site-specific and should not be extrapolated to locations with completely different climatic conditions.