NITRATE LEACHING UNDER IRRIGATED CORN

Nitrate leaching was measured under no-till and conventional tillage i rrigated corn on a sandy loam soil. Ground water was sampled monthly f or two years. Soil samples were taken three or four times a year to a depth of 150 cm. Nitrate concentrations were above 10 mg/L for most sa mpling dates. Most of the nitrogen was leached during the fall and win ter months. The mass of nitrate leached from the no-till plots ranged 55.0 to 78.8 kg/ha/yr. The mass of nitrate leached from the convention al plots ranged from 57.1 to 94.0 kg/ha/yr. The mass of nitrate leache d was slightly higher under conventional tillage than no-till. Nitrate leaching would be difficult to control, because most of the nitrogen is leached during the late fall and winter. Proper nitrogen applicatio ns for realistic yield goals is probably the best method for controlli ng nitrate leaching.