Nutrient Source and Tillage Impact on Corn Grain Yield and Soil Properties

Large amounts of animal manure, particularly poultry litter and dairy manure, are generated in southeastern United States, where corn (Zea mays L.) is also extensively grown. Characterizations of management practices and long-term manure and soil nutrient dynamics are critical. This study examined corn grain yield and soil nutrient status under three nutrient sources (two rates of each) as follows: inorganic fertilizer, poultry litter, and dairy manure compared with a nontreated control under two tillage practices (no-till and incorporated). Treatments were replicated four times in a split-plot design from 2004 to 2007. Soil samples were taken annually in the spring before treatment application to evaluate the status of the residual nutrients in soil. Significant differences in corn grain yield between the two tillage practices (main effect) were observed in all 4 years. The high rate of poultry litter application produced similar grain yield as inorganic fertilizer. However, results from dairy manure were not as consistent as poultry litter. After 4 years of poultry litter application, Mehlich-3 (M-3) phosphorus (P) increased from an initial 31.4 to 63.0 mg kg(-1) for the 4.5 Mg ha(-1) year(-1) rate and to 178 mg kg(-1) for the 13.5 Mg ha(-1) year(-1) rate. More specifically, 5.2 kg ha(-1) year(-1) of P applied as poultry litter increased soil M-3 P by 1 mg kg(-1) after 4 years of application. Results indicated that poultry litter is a primary fertilizer at the rate of 13.5 Mg ha(-1) applied in four consecutive years on a silt loam soil-produced corn grain yields similar to inorganic fertilizer under both no-till and incorporated systems and did not result in residual soil test P, Cu, and zinc levels considered to be harmful to surface water or cropping systems.