CORN YIELD AND NITROGEN UPTAKE AS INFLUENCED BY TILLAGE AND APPLIED NITROGEN

No-till management systems have been reported to reduce nonpoint source (NPS) pollution from agricultural fields. However, questions have been raised concerning the fate of nitrogen (N) in these systems. Increased moisture conservation and reduced runoff from no-till systems have the potential to accelerate leaching of nitrate (NO3) out of the root zone, thus altering the problem from one of surface water degradation to one of ground water pollution. However, it is also probable that the additional moisture conserved in no-till systems result in increased crop yield and N uptake. Time of N application and source of N could influence yield and N recovery and thus limit N losses during critical periods. A 3-year study was conducted to determine if the fate of N applied to nonirrigated corn (Zea mays L.) would be influenced by tillage system, N rate, and time and source of N application. This paper addresses the impact of these practices on yield and N uptake. The experimental site was located on a Typic Hapludult that is characteristic of finer-textured soils used for continuous corn production. Management practices evaluated were conventional-till vs, no-till, rate of N application, inorganic N vs, sewage sludge N, and preplant vs. split application of N. Yield and N recovery were, respectively, 19 and 22% higher in no-till compared with conventional-till systems at the point of maximum yield. Corn yield and N uptake were both increased when sewage sludge was applied compared with either split or preplant application of inorganic N. No differences were observed in corn yield and N uptake between preplant and split application of N. These studies were conducted during years with drier than normal growing seasons, and the results indicate that the higher moisture present in the no-till system may have contributed to increased yield and N recovery. The increased N recovery reduces the quantity of N remaining in the soil profile that might be lost, due to leaching, after crop harvest.