Corn crop water stress index under different redroot pigweed (Amaranthus retroflexus L.) densities and irrigation regimes

Abstract

Crop water stress index (CWSI) is a valuable index for quantifying water stress. To evaluate the CWSI of corn under redroot pigweed densities, a study was conducted at Shiraz University during 2008. The main objective was to develop baseline equations, which could be used to calculate CWSI for monitoring water status of corn under weed competition. Six weed densities and three irrigation treatments were selected. Six lower baselines with different slopes and intercepts between Tc − Ta (canopy-air temperature difference) and VPD (vapor pressure deficit) were fitted for each weed density. With increasing redroot pigweed density, lower baseline slope and its intercept were significantly increased due to more limitation in water. Monthly and seasonal mean CWSI were lowest in weed free and T2 treatment (high water supply) and highest in 80 weeds m−2 and T3 (water stress) treatment, which could show higher competition between corn and redroot pigweed at higher weed densities. An average of mean seasonal CWSI (about 0.12) in weed free and T2 treatment produced the maximum kernel yield. Predicting yield response to seasonal mean CWSI is important in developing strategies for farmers, and researchers for irrigation management under limited water conditions.