Water Productivity of Corn and Dry Bean Rotation on Very Fine Sandy Loam Soil in Western Nebraska

Abstract

<abstract><title><italic>Abstract. </italic></title> Subsurface drip irrigation (SDI) was used to irrigate corn and dry beans in a crop rotation study for four years from 2005 to 2008 to evaluate the accumulative effect of irrigation amount on yield and irrigation water use efficiency (I_WUE). This study was conducted on a very fine sandy loam soil using a short season corn hybrid typical for the area. Four irrigation treatments based on providing a fraction of the estimated crop evapotranspiration (ET_c) were evaluated. The treatments were designed to replace a certain percentage of ET_c and were denoted as I₁₂₅, I₁₀₀, I₇₅, and I₅₀where the subscript indicates the percentage of ET replacement. The ET_c was accumulated, subtracting rain and irrigation amounts, to estimate soil water depletion. Irrigations were made at the various percentages when estimated depletion exceeded the I₁₀₀irrigation amount. The average corn yield response to applied irrigation water was 10.5 kg ha^-1 mm^-1 (excluding the I₁₂₅ treatment). Corn yield was generally statistically different between the I₁₂₅ and I₁₀₀ treatments and each of the I₇₅ and I₅₀ treatments in dry years. Average dry bean yield response to irrigation was 1.5 kg ha^-1 mm^-1. Dry bean yield was not statistically different. I_WUE was calculated by subtracting a representative dryland yield from the measured yield and then dividing by the amount of irrigation water applied. Average I_WUE for corn ranged from 17.8 kg ha^-1 mm^-1 for I₁₂₅ to 31.1 kg ha^-1 mm^-1 for I₅₀ and was not statistically different among all treatments overall due to a year interaction. Corn I_WUE values were generally statistically different between I₅₀ and I₁₂₅ in most years. Values for corn I_WUE were similar for I₁₀₀ and I₇₅ treatments. Average I_WUE for dry beans ranged from 4.55 kg ha^-1 mm^-1 for I₁₂₅ to 9.15 kg ha^-1 mm^-1 for I₅₀. Bean I_WUE values for the I₅₀ irrigation treatment were generally greater than the others, especially in dry years. Maximum corn yield occurred with 300 mm of irrigation water in a wet year and approximately 375 mm in dry years. For this study, dry bean yield was highly variable, partly due to treatments being over-watered when based on ET_c estimates developed for sprinkler irrigation. Bean yield showed little increase for irrigation amounts greater than 300 mm. Further research is needed examining smaller levels of irrigation, including dryland treatments, as well as different timing treatments based on actual soil water and crop stage of growth.