Yield response of corn to timing of a limited seasonal irrigation depth (150 mm) with subsurface drip irrigation

Deficient water supplies in many areas of the High Plains of the USA are forcing many farmers to produce corn (Zea mays L.) under deficit irrigation conditions. When water is limited, it is especially important to know.how to time irrigations to optimize yield and water use efficiency. The objective of this study was to evaluate the effect of application timing of a fixed and deficient seasonal irrigation depth (150 mm) on grain yield, yield components, and water use characteristics of corn irrigated with subsurface drip irrigation 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. Eight irrigation treatments (T1-T8) were evaluated, which consisted of dividing the application of 150 mm of water in different proportions during the months of July, August, and September. Irrigation timing resulted in significant differences in yield and actual seasonal evapotranspiration (ET _d). Yields were positively and linearly correlated to seasonal ET _d and to the ratio of ET _d and crop evapotranspiration with no water stress (ET _w). Although all treatments received the same seasonal irrigation depth, seasonal differences in ET _d among treatments were as much as 70 mm (2.8 in), which resulted in yield differences of approximately 2 Mg ha ^-1 (32 bu Ac ^-1). Irrigation timing also affected grain test weight and grain moisture. The treatments that received all of the irrigation water in July and August resulted in the highest seasonal ET _d, ET _d/ET _w, and grain yield. The opposite occurred with the treatment that received most of the irrigation water in September. These results point out the importance of proper irrigation scheduling to assure that irrigation is applied at the time needed to prevent crop stress, especially at the times of high ET _d rates when stress can reduce seasonal ET _d the most and consequently has a greater effect on yield.