Dormant-Season Irrigation: Grain Yield, Water Use, and Water Loss

Research results are lacking that compare the yield benefit from a limited amount of irrigation water applied off-season vs. in-season. Also lacking is a partitioning of field water losses during winter into the profile drainage and evaporation components. The objectives of this work were: (i) to examine grain yield and water use of corn (Zea mays L.) and Winter what (Triticum aesrivum L.) in irrigation schemes that use fall vs. spring irrigations; and (ii) to partition field water loss during winter into the profile drainage and evaporation components. The field work was done near Tribune, KS, on a Ulysses silt loam soil (fine-silty, mixed, mesic Aridic Haplustoll). Timing of the off-season irrigation (fall vs. spring) did not influence corn grain yield. In irrigation schemes identical except that off-season irrigation was or was not applied, off-season irrigation did not influence corn grain yield significantly. Maximum grain yield benefit in corn from irrigation was achieved when water was applied in-season. In winter wheat receiving only one irrigation, fall irrigated wheat yielded 2055 kg ha⁻¹ more grain (3-yr mean) than wheat irrigated only in spring. Among the irrigation schemes containing fall irrigation, there was no significant difference in winter wheat grain yield, even though the total irrigation amount ranged from 152 to 456 mm. Drainage losses during winter were less than 5% as much as evaporation losses at mean profile water contents during winter of less than 50% available soil water. At greater than 50% available soil water, the relative contribution of drainage in profile water loss increased with increasing profile water content. Drainage losses equalled evaporation losses at a mean profile water content during winter of 0.57 m (80% available soil water). Off-season irrigation of corn was not a water efficient practice. Fall irrigation of winter wheat was a water efficient practice that allowed continuous cropping in a region where some rotation that includes fallow is the dryland alternative.