Soil profile modification effects on corn and sugarbeet grown with limited water

In arid and semiarid areas, searches continue for practices that enhance soil water storage and for crops that make the best use of stored water. Objectives of this study were to determine the effects of profile modification (PM) on profile soil water extraction, water use, yield, and water-use efficiency (WUE) of corn (Zea mays L.) and sugarbeet (Beta vulgaris L.) grown with limited water supply. The study was conducted on a site where PM treatments involving mixing of the sod profile to 0.0, 0.9, and 1.5 m were imposed on Pullman clay loam (fine, mixed, thermic Torrertic Paleustoll) in 1964. Corn (3 yr) and sugarbeet (2 yr) were grown under limited water (growing-season rainfall plus preplant and emergence or preplant irrigation only). Profile modification to 0.9 and 1.5 m increased the 3-yr-average corn yields 64 and 180%, respectively. Respective increases in water use were 11 and 20%. Sugarbeet yields and water use were not affected the first year but yields decreased and water use increased by 11% (on 1.5-m PM soil) in the second year. Depletion curves indicated little rooting by corn below 2 m. Sugarbeet used water from 2.7 m or deeper on all PM treatments, with greatest use on the 1.5-m PM soil. Profile modification to 1.5 m increased sod water depiction from the 0.7- to 2.7-m soil depth by corn 186% (49-140 mm) and by sugarbeet 31% (179-234 mm). Extensive rooting by sugarbeet and the long vegetative growing season for root extension limited PM effects on rooting and associated depletion of water from soil below the depths of PM. With the tested system of PM and water supply, corn yields were too low to make production profitable (average 2.8 Mg ha-1 on 1.5-m PM soil) and the effects of PM on sugarbeet yields and WUE do not indicate that PM is a viable practice in sugarbeet production.