Grain Yield and Root Distribution Under Limited Irrigation Management.

Reduced irrigation water supply due to recent drought, well curtailments, municipality demand for irrigation water, and low mountain snow accumulations has reduced irrigation water for agriculture in Colorado and other areas of the western U.S.    Limited irrigation water supplies have increased our need to understand how best to irrigate corn (zea maize) when available water supplies do not meet crop evapotranspiration (ET) requirements.  Researchers from Colorado State University have conducted limited irrigation demonstrative research for three years producing corn on Julesburg Sandy Loam soil near Greeley, Colorado.  Demonstrative research plots were furrow irrigated from surface water supply.  Timing of irrigation events was based on plant development stage and ET demand to optimize irrigation input.   Two irrigation treatments (limited and full) were replicated two times.    Irrigation inputs were near sixty-percent of full ET for limited irrigation treatments and 100 percent or greater of full ET requirements for full irrigation treatments.  Corn grain yields have been consistently near seventy-percent for limited irrigation treatments relative to full irrigation.  During 2008 and 2009 investigations, three varieties (DeKalb DKC 52-59, NC+ 4250R, Pioneer 35F44) were evaluated for root distribution to 1.5 m soil depth.  Two soil cores 7.62 cm X 1.5 m were sampled and combined from each plot.  Soil samples were taken between the corn plant and irrigation furrow center, 19 cm from the plant base.  Samples were refrigerated and root washed.  Roots from each composite sample were collected and refrigerated in 1:1 methyl alcohol and distilled water.  Root samples were then scanned using Adobe computer software to determine total area of roots.  Following root area determinations, samples were dried and weighed to determine mass distribution of roots as a function of soil depth and irrigation treatment.  Results from 2008 indicate that plant population and irrigation treatment did not impact root distribution as a function of soil depth.