Effect of Crop Residue on Soil Water Content and Yield of Deficit-Irrigated Corn and Soybean

It is believed that reduced tillage, with more crop residue on the soil surface, conserves water, especially in arid and semi-arid climates. However, the magnitude of water conservation is not clear. In 2007, a study was initiated on the effect of residue on soil water content and crop yield at North Platte, Nebraska. The experiment was conducted on plots planted to field corn (Zea mays L.) in 2007 and 2008, and soybean (Glycine max) in 2009. There were two treatments: residue-covered soil and bare soil. Bare-soil plots were created in April 2007 by using a dethatcher and subsequent hand-raking. In April 2008 and 2009, bare-soil plots were recreated on the same plots as in 2007. The experiment consisted of eight plots (two treatments with four replications each). Each plot was 12.2 m by 12.2 m. The crop was sprinkler-irrigated, but purposely water-stressed, so that any water conservation in the residue-covered plots might translate into higher yields. In 2007, mean corn yield was 12.4 Mg ha-1 in the residue-covered plots and 10.8 Mg ha-1 in the baresoil plots. Other research has shown that it takes 65-100 mm of irrigation water to produce this extra 1.6 Mg ha-1, which may be considered water conservation due to the residue. In 2008, the residue covered soil held approximately 60 mm more water in the top 1.83 m compared to the bare soil towards the end of the growing season. In addition, mean corn yield was 11.7 Mg ha-1 in the residue covered plots and 10.6 Mg ha-1 in the bare-soil plots. It would take 30-65 mm of irrigation water to produce the difference. Thus, the total amount of water conservation due to the residue was 90-125 mm in 2008. In 2009, the residue-covered soil held approximately 90 mm more water in the top 1.83 m compared to the bare soil towards the end of the growing season. Also, mean soybean yield was 4.5 Mg ha-1 in the residue-covered plots and 3.9 Mg ha-1 in the bare-soil plots. Between 70-90 mm of irrigation water would be required to produce the difference