Managing spatial variability with furrow irrigation to increase nitrogen use efficiency

With experience gained from two yr of demonstrations, two research projects were initiated in the fall of 1993 to investigate the potential for variable rate nitrogen (N) application to improve N use efficiency, and reduce N loss to the environment. One study is being conducted under sprinkler irrigation at sites in the central Platte valley and the Sandhills of Nebraska. The other is being conducted at three furrow-irrigated sites in south-central and west-central Nebraska. The furrow-irrigation study is evaluating how the spatial trend of water infiltration and leaching inherent to furrow irrigation can be accounted and managed for. Ideally, infiltration functions and intake opportunity times would be measured on the same grid interval as other soil and crop parameters, and used to develop infiltration estimates using volume balance techniques. Using volume balance techniques, an infiltration profile for each observed furrow can be developed, from which infiltration at any point down the furrow can be estimated.