Corn yield response to different irrigation depths with subsurface drip irrigation

Quantifying the yield response of crops to water inputs is important for establishing adequate irrigation scheduling strategies. The objective of this study was to evaluate how different seasonal irrigation depths applied to corn (Zea mays L.) affected the soil water balance, corn water use, corn yield, and yield components in a semiarid climate. The study was conducted during 2005 at the University of Nebraska-Lincoln West Central Research and Extension Center at North Platte, NE. Six irrigation treatments were evaluated, which received incremental seasonal irrigation depths ranging from 53 to 254 mm using a subsurface drip irrigation system. For each treatment, a water balance approach was used to estimate several water variables, including daily and seasonal actual crop evapotranspiration (ET _d), crop evapotranspiration when water is not limited (ET _w), evaporation (E), transpiration (T), and deep percolation. All treatments were deficit-irrigated, and total water (soil water + rain + irrigation) was enough to produce seasonal ET _d values between 81 and 98% of seasonal ET _w. Seasonal irrigation affected ET _d, especially its T component. Although E was a significant portion of ET _d, it was mostly due to rainfall and was not affected by irrigation. Grain yield was linearly related to seasonal irrigation (yield=0.0123x+9.52,r ²=0.94), total water (yield=0.0123x+3.01,r ²=0.94), ET _d (yield=0.0212x-1.77,r ²=0.85) and ET _d/ET _w (yield=14.08x-;1.37,r ²=0.89). Seasonal irrigation also affected grain moisture, grain test weight, stover moisture, and the dry weights of the stover, grain, and cob. The percent of the above-ground plant dry weight represented by each component (grain, stover, and cob) was practically constant among irrigation treatments. On average for all treatments, the grain, stover, and cob accounted for 57.9 (= harvest index), 33.5 and 8.6 % of the above-ground plant dry weight, respectively.