North Central Extension-Industry Soil Fertility Conference. 2011. Vol. 27. Des Moines, IA. Page 83 CORN RESIDUE HARVESTING EFFECTS ON YIELD RESPONSE TO N FERTILIZATION J.L. Pantoja, J.E. Sawyer, D.W. Barker, and M. Al-Kaisi Iowa State University, Ames, IA Introduction Producers have many choices of diverse tillage practices for their corn (Zea mays L.) production systems. However, no-till has become an important soil management practice to help reduce water and wind erosion, as well as nutrient runoff, while conserving soil moisture for crop use. No-till systems also help farmers by saving labor and time, as well as reducing farm costs due to less equipment and fuel consumption. Nevertheless, no-till production is typically more successful and has higher crop yield on moderately to well drained medium-textured soils (Bitzer, 1998), compared to soils with poor internal drainage and high clay. The increased use of corn biomass for livestock feed, bedding, or a bioenergy resource is an ongoing issue in the Midwest U.S. The removal of corn residue from fields reduces the amount of plant material remaining for soil surface protection, reduces carbon return to soil and potential soil organic matter, and alters the cycling of plant nutrients. This could potentially affect nutrient availability for crop use. Therefore, it is necessary to evaluate the short and long-term impacts of corn residue removal and residue return on soil properties and nutrient supply to crops. Concerns about nitrate (NO 3 - -N) loss in drainage water as the major contributor of N loading to the Gulf of Mexico has also led to increasing efforts for alternative management practices to reduce NO 3 - -N loss from corn fields in the Midwest U.S. Mehdi et al. (1999) discussed the importance of identifying tillage practices which maximize corn N uptake and the associated need to determine N fertilization recommendations tailored to those systems that minimize N loss. A similar need is required for systems where corn residue is harvested. Compared to tillage, no-till may result in lower yield but not necessarily change response to N management practices (Vetsch and Randall, 2004). Also, corn residue removal can change yield response to tillage system, and optimal N fertilizer requirements (Coulter and Nafziger, 2008). The agronomic and environmental impacts of tillage and corn residue removal practices are still in debate. Effective N management needs to enhance N fertilizer efficiency without resulting in yield reductions due to inadequate N (Andraski and Bundy, 2008). The determination of optimal N fertilization rates for achieving optimal yields is difficult due to the complexity of N cycling, which can be altered with different soil tillage and cropping practices, such as grain or combination grain-residue biomass removal. The objectives of this study are to evaluate tillage system, corn residue removal rate, and N fertilizer rate on corn yield response and N fertilization requirement in continuous corn. Materials and Methods Field sites were established in the fall of 2008 at two Iowa State University research and demonstration farms representing contrasting regions, soils and drainage class, and climatic