Submitted to: Annual Southern Conservation Tillage Conference for Sustainable Agriculture
Publication Type: Proceedings
Publication Acceptance Date: 5/15/2004
Publication Date: 6/8/2004
Citation: Endale, D.M., Schomberg, H.H., Jenkins, M., Cabrera, M.L., Radcliffe, D.R., Hartel, P.G., Shappell, N.W. 2004. Tillage and N-fertilizer source effects on yield and water quality in a corn-rye system. Annual Southern Conservation Tillage Conference for Sustainable Agriculture. p. 37-48. CDROM. Raleigh, North Carolina. Interpretive Summary: The nation-wide concern with pollution, especially from agricultural sources, means that consequences of tillage and nutrient source choices for farming need to be carefully measured both in terms of agricultural and environmental impacts. Growers in the South increasingly are using poultry litter and no-tillage to raise crops. Although poultry litter is an excellent source of plant nutrients, it could be a source of nitrate, phosphate and the hormones estradiol and testosterone (shown to affect reproductive development in animals). No-tillage generally induces better infiltration, which increases plant available water that could lead to better crop yields, but it might encourage migration of these pollutants towards ground water. In three years of study, scientists at the USDA Agricultural Research Service, J. Phil Campbell Sr. Natural Resource Conservation Center in Watkinsville, GA, and the Crop and Soil Sciences Department at the University of Georgia, Athens, GA, compared agricultural benefits and water quality impacts of growing corn with a rye cover crop in either no-tillage or conventional tillage, and fertilizing with either poultry litter or conventional fertilizer. Managing corn with no-tillage and/or poultry litter at normal nitrogen application rates increased corn yield by 15 to 27% but did not present large additional risks of nitrate or hormone contamination of water resources. However, dissolved phosphorus level coming off the land is a concern. This information can be used by corn growers, commodity groups, extension agents, and federal agencies to increase production of corn, a crop valued at over $21 billion in 2001, without unduly creating environmental hazard.
Technical Abstract: Tillage and nutrient source choices have important agronomic and environmental consequences in cropping system management, which need to be quantified in the Southeast. In three years of research at the USDA-ARS, J. Phil Campbell Sr. Natural Resource Conservation Center, Watkinsville, GA, we compared agronomic benefits and water quality impacts of four treatments combined farm no-till, conventional-till, poultry litter and conventional fertilizer in a corn-rye cropping system. No-till and poultry litter each enhanced corn yield by 15 to 23% over three years. When combined, they enhanced yield by 27%. Nitrate-nitrogen (NO3-N) and ammonium-nitrogen (NH4-N) off-site losses through runoff or drainage were similar among treatments. Concentrations of NO3-N and NH4-N were dependant on N application rates. Below a 3 ton acre-1 application rate of poultry litter (90 lbs N acre-1), nitrate levels are expected to be below 10 ppm, especially if the first precipitation or irrigation event is delayed after N application. Application of poultry litter increased loss of ortho-phosphate in runoff by 5 to 6 times compared to conventional fertilizer. The sex hormones estradiol and testosterone running off poultry litter plots were not above levels observed for conventional fertilizer