TILLAGE AND NITROGEN MANAGEMENT EFFECTS ON NITRATE-NITROGEN IN THE SOIL-PROFILE

A field study was conducted on Nicollet loam soils to determine the ef fects of tillage and nitrogen (N) management on the residual nitrate-n itrogen (NO3-N) in the soil profile. Two replications of two tillage s ystems (no-till and moldboard plow) and two N management practices (si ngle application of N at the rate of 175 kg/ha and three applications totaling 125 kg/ha) were used for continuous-corn production. Soil sam ples were taken periodically each year to a depth of 150 cm at three l ocations within each of the six experimental plots (9 m apart, one alo ng and two on either side of a tile drain running down the center of t he plot). No-till and three N applications with a lower total applicat ion rate reduced the residual NO3-N in the soil profile. Regression an alysis of the data showed less residual NO3-N under no-till system hav ing a definite decreasing trend with depth. Eight years (1984-1991) of data indicate that corn yields were not affected by tillage or N mana gement practices.