Carbon Dioxide and Water Level Effects on Yield and Water Use of Winter Wheat

Abstract

AbstractIncreasing levels of atmospheric CO2 may have major effects on yield and water use of winter wheat (Triticum aestivum L.). The objective was to determine the effect of elevated levels of CO2 on grain yield and water use from planting to harvest under two water levels. ‘Newton’ winter wheat was grown in the field under ambient (340 µL/L) and elevated levels (485, 660, and 825 µL/L) of CO2, during three growing seasons, in 16 underground boxes (77 cm long, 37 cm wide, and 180 cm deep) containing a Muir silt loam (finesilty, mixed, mesic Cumulic Haplustoll). Water in half of the boxes was maintained at 0.38 m3/m3 (high water level) and in the other half between 0.14 to 0.25 m3/m3 (low water level). Boxes were weighed in the fall and spring to determine the amount of water use by transpiration. Plastic chambers (121 by 92 by 168 cm) covered the boxes to maintain different CO2 levels. Grain yield of the high‐water‐level wheat grown under ambient CO2 was about the same as the grain yield of low‐water‐level wheat grown at the highest level of CO2 (825 µL/L) (3‐yr means: 725 and 707 g/m2, respectively). Similar results were obtained for yield components (spike number, spike weight, kernels/spike, and kernel weight). High‐water‐level wheat grown with 825 µL/L CO2 transpired more water than low‐water‐level wheat grown under ambient levels of CO2 (3‐yr means: 453 and 370 L/m2, respectively). Under high and low water levels, 29 and 31% less water was required, respectively, to produce a gram of grain when the CO2 concentration was raised from ambient to 825 µL/L. Results show that the water requirement of wheat is reduced by about 30% by elevated (1.4 times present ambient) CO2.