Yield determination in winter wheat under different water regimes

Abstract

Wheat (Triticum aestivum) is grown in a wide range of water regimes and produces both grain and forage in the U.S. Southern Great Plains (SGP). Despite being relatively adapted to water stress, decreased water supply has become the main abiotic factor limiting wheat yield in the region. A 5-yr field study was conducted to investigate the yield determination in winter wheat under a center pivot irrigation system. Twenty elite wheat cultivars were grown at four water regimes, I100, I75, I65, and I50 to meet 100%, 75%, 65%, and 50% evapotranspiration (ET) requirement, respectively. The 2011 and 2013 seasons had all irrigation levels, while there were only two irrigation levels in 2012 (I50 and I65) and 2014 (I75 and I100), and three irrigation levels in 2015 (I50, I75, and I100). In most seasons, ET, biomass, and grain yield decreased consistently from higher to lower water regime, but water use efficiency (WUE) and harvest index (HI) were the highest at I75. Averaged across all years and genotypes, grain yield was reduced by only 5% from I100 to I75 indicating that reducing irrigation to meet 75% of ET requirement can still achieve similar yield to I100 and maximize HI and WUE. Newer cultivars including Duster, Endurance, Winterhawk, TAM 112, and TAM 113 had greater yield at I50 compared to other cultivars. Grain yield showed a strong relationship with biomass, HI, and ET. At lower water regimes (I50, I65), all three yield components (spikes per square meter, seeds per spike, and kernel weight) were correlated to grain yield. At higher water regimes (I75 and I100) grain yield was consistently related to kernel weight. This study demonstrated that high yield can be achieved at an irrigation level of I75. In addition, planting newer drought tolerant cultivars may provide yield benefits under water-limited conditions in the SGP.