Nonpoint Nitrate Contamination of Ground Water in Merrick County, Nebraska a

The areal distribution of 293 samples from the ground water of Merrick County, Nebraska has definite patterns of high (>20 ppm), intermediate (10–20 ppm), and low (<10 ppm) nitrate‐nitrogen concentrations. Where contamination is present the nitrate‐nitrogen concentrations are relatively homogeneous indicating large diffuse nonpoint sources. SYMAP (gray‐scale mapping) indicates exceptionally good correlation between the irrigated coarse‐textured soils and the higher nitrate‐nitrogen levels. The obvious implication is that the nitrate‐nitrogen levels are directly dependent on the leaching of nitrogenous material dispersed in or on the coarser‐textured soils. The widespread use of commercial nitrogen fertilizer on irrigated corn acreages is suspected of being the major contributor of nitrate to the ground water.