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

No-till management systems have been reported to reduce nonpoint sourc e (NPS) pollution from agricultural fields. However, questions have be en raised concerning the fate of nitrogen (N) in these systems. Increa sed 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 t he additional moisture conserved in no-till systems result in increase d 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 critica l 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 till age system, N rate, and time and source of N application. This paper a ddresses the impact of these practices on yield and N uptake. The expe rimental site was located on a Typic Hapludult that is characteristic of finer-textured soils used for continuous corn production. Managemen t practices evaluated were conventional-till vs, no-till, rate of N ap plication, inorganic N vs, sewage sludge N, and preplant vs. split app lication of N. Yield and N recovery were, respectively, 19 and 22% hig her in no-till compared with conventional-till systems at the point of maximum yield. Corn yield and N uptake were both increased when sewag e sludge was applied compared with either split or preplant applicatio n of inorganic N. No differences were observed in corn yield and N upt ake between preplant and split application of N. These studies were co nducted during years with drier than normal growing seasons, and the r esults 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 th at might be lost, due to leaching, after crop harvest.