Water and Nitrogen Management in Central Platte Valley of Nebraska

Contamination of ground water by nitrogen leached from fertilizer on irrigated soils is related to the quantity of nitrate‐N $({\mathrm{NO}}_3^{-}‐N)$ present, the leaching potential based on soil texture and percent depletion of available soil water in the root zone, and the amount of water entering the soil profile. Research and demonstration projects in the central Platte valley of Nebraska have shown that ${\mathrm{NO}}_3^{-}‐N$ leaching is influenced by both irrigation and fertilizer‐nitrogen (N) management in corn production. Scheduling irrigation according to available soil‐water depletion can reduce deep percolation to a certain extent. Additional reduction in deep percolation can be achieved by improving efficiency of water application, particularly on furrow irrigated fields. Testing for ${\mathrm{NO}}_3^{-}‐N$ in irrigation water and soil can provide for substantial reductions in fertilizer N application, if residual levels in the soil are high, or if considerable ${\mathrm{NO}}_3^{-}‐N$ will be applied with irrigation water. Grain yields were not appreciably affected by the use of these management practices, while in most cases input costs for fertilizer nitrogen and irrigation water were reduced.