Effects of Water Deficits on Yield, Yield Components, and Water Use Efficiency of Irrigated Corn 1

Irrigated corn ( Zea mays L.) is an important feed grain crop on the Southern High Plains where the supply of water for irrigation is declining. Limited irrigation‐applying less water than is required to meet potential evapotranspiration‐is extensively practiced on the drought tolerant crops of grain sorghum [ Sorghum bicolor (L.) Moench], wheat ( Triticum aestivum L.), and cotton ( Gossypium hirsutum L.). The purpose of this paper is (i) to report the effects of timing and duration of water deficit periods on growth and yield components of corn, (ii) to evaluate the seasonal evapotranspiration requirements of corn, and (iii) to give further information regarding the adaptation of corn for limited irrigation in a region of normally high evaporative demand climate. In a 4‐yr study, corn was grown under five irrigation treatments: adequate water, 2‐ and 4‐week water deficit periods during vegetative growth, and 2‐ and 4‐week water deficit periods during grain filling. Water deficits imposed 41 days after planting reduced leaf, stalk, and ear yields, while those imposed 55 days after planting reduced only stalk and ear yields. Deficits during vegetative growth reduced kernel numbers but had little effect on weight per kernel. Deficits during grain filling did not affect leaf and stalk yields but reduced ear yields. Kernel numbers were not affected by water deficits during grain filling unless severe deficits were imposed early in the period; thus, grain yield reductions were proportional to reductions in weight per kernel. With adequate water, seasonal water use averaged 964 mm on graded furrows and 834 mm in level borders. Although water use efficiency (WUE) was sometimes increased slightly when plants were subjected to water deficits, the data indicate that limited irrigation of corn would not be feasible on the Southern High Plains.