Submitted to: Nutrient Cycling in Agroecosystems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/7/2009
Publication Date: 9/22/2009
Publication URL: http://www.springerlink.com/content/100322/?k=endale
Citation: Endale, D.M., Schomberg, H.H., Jenkins, M., Franklin, D.H., Fisher, D.S. 2010. Management implications of conservation tillage and poultry litter use for Southern Piedmont USA cropping systems. Nutrient Cycling in Agroecosystems. On-line. DOI 10.1007/s/0705-009-938-Z. 88:299-313.
Interpretive Summary: Integrated studies of agricultural system are needed so that we can understand interactions between multiple parts of the system. Over a 14 year period, researchers at the USDA-ARS in Watkinsville GA, in cooperation with researchers at University of Georgia in Athens GA, examined the many interactions occurring within conventional and conservation tillage systems incorporating conventional or alternative fertilizer sources (poultry litter). The study was conducted on a facility instrumented to measure runoff and drainage. No-till had more drainage and less runoff then conventional tillage differences emerging two years into the no-till operation. Cover crops effectively reduced nitrate losses in subsurface drainage. Improvements in soil quality were observed with conservation tillage and poultry litter over the last 10 years of the research. Soil carbon and nitrogen increased as did earthworm populations. Poultry litter alone and in combination with no-till greatly enhanced corn and cotton production. After 10 years of poultry litter use some nutrients and metals (P and Zn) had accumulated to excessive levels. This occurred because poultry litter was applied based on the nitrogen requirement of cotton and corn. No-till and poultry litter led to elevated dissolved phosphorus concentration in runoff. Although fecal indicator bacteria (E. coli and fecal enterococci), and the hormones estradiol and testosterone were detected in subsurface drainage and overland runoff there was no difference between the fertilizer and tillage treatments. Economic and ecological factors must be balanced to insure sustainability of agricultural systems and may not be apparent until sufficient time has passed to elucidate clear patterns or shifts. System responses might have been different during drought in six of the fourteen year of study than they would have been under normal precipitation periods. Such long-term and holistic datasets are needed by producers, extension and regulatory agency personnel to meet sustainable management goals.
Technical Abstract: Soil and water resources must be protected to meet the growing need for food production in the 21st century. Greater adoption of conservation tillage and judicious use of animal manures as fertilizers will be needed to meet this challenge. Identifying and understanding the many interactions occurring within agricultural systems is fundamental to developing sustainable systems for soil and water protection. In the early 1990’s researchers from USDA-ARS at Watkinsville, Georgia, and the University of Georgia began investigating multiple interactions within conventional and conservation cropping systems that included poultry litter (PL) as a nutrient source. Increases in C and N with conservation tillage and PL resulted in improved soil structure that altered the infiltration rate on the instrumented plots. Runoff decreased in conservation tillage but drainage increased raising the risk of leaching of nitrate into the soil profile. However, early work showed that the presence of a rye cover crop during the winter reduced the losses of N compared to no cover crop or a legume cover crop. Biological activity as indicated by earthworms was greater with conservation tillage and PL. Soil nutrient accumulation, particularly P and Zn, began to increase due to use of poultry litter in corn production reaching excessive levels in few years due to higher rates needed to meet the demand of corn. No-till and poultry litter led to elevated dissolved phosphorus concentration in runoff. During this same time, losses of fecal indicator bacteria (E. coli and fecal enterococci), and the hormones estradiol and testosterone were observed in subsurface drainage and overland runoff but they were similar across all treatments indicating that other environmental factors were controlling these organisms and hormones. In all but the very driest years, yields of cotton and corn increased 20 to 35% with conservation tillage and poultry litter. In our analysis, economic benefits were proportional to environmental risks up until when the soil P and Zn concentrations became excessive; at that point use of poultry litter became a negative within the system. Other risk factors were not large enough to alter the management practices being implemented. However, drought in six of the fourteen years of research might have contributed to this.