Tillage and Nitrogen Management Effects on Nitrate-Nitrogen in the Soil Profile

A field study was conducted on Nicollet loam soils to determine the effects of tillage and nitrogen (N) management on the residual nitrate-nitrogen (NO3-N) in the soil profile. Two replications of two tillage systems (no-till and moldboard plow) and two N management practices (single application of N at the rate of 175 kg/ha and three applications totaling 125 kg/ha) were used for continuous-corn production. Soil samples were taken periodically each year to a depth of 150 cm at three locations within each of the six experimental plots (9 m apart, one along and two on either side of a tile drain running down the center of the plot). No-till and three N applications with a lower total application rate reduced the residual NO3-N in the soil profile. Regression analysis of the data showed less residual NO3-N under no-till system having a definite decreasing trend with depth. Eight years (1984-1991) of data indicate that corn yields were not affected by tillage or N management practices