Potential nitrogen contamination of ground water as affected by soil, water, and land-use relationships. Technical report, 1 Apr 89-31 Mar 90

To assess nitrate leaching to soil profile characteristics and its association with land use, suction lysimeters were installed in production alfalfa and corn fields and in an adjacent hardwood forest. The amount of N at approximately one meter depth in the soil was greatest in the corn (averaged about 26 ppm N for the year), was less in the alfalfa (averaged about 16 ppm N for the year), and was just above the level of detection (about 0.2 ppm N for the year) in the hardwood forest. N availability is reduced in the second year following alfalfa reducing yield and quality of corn. These effects are more pronounced in no-tillage and ridge-tillage than in conventional tillage systems. Total inorganic N contents in the 0-60 cm soil profile did not vary between tillage or N treatments. The manured soils had significantly higher profile inorganic N contents in July, 1989. Soil nitrate and ammonium levels and potato petiole nitrate concentrations were directly related to the rate of N application and declined with time. Tuber size was significantly improved by either 60 or 120 pounds/acre rate of sidedress N. Specific gravity of potato tubers was unaffected by N application rate.