2010 Annual Report
1a.Objectives (from AD-416)
The objective of this cooperative research project: (1) determine the impacts of broiler litter quality and quantity on forage grass productivity, on forage quality, and on accumulation of excess nutrients in soil; (2) test the effects of two cutting heights (1¼ and 3½ inches) and three harvest intervals (21, 35, and 49 days) on yield of hay and manure nutrients, particularly phosphorus (P); (3) test the effects of year-round forage production on remediation of excess soil P; and (4) determine changes in soil chemistry and fertility due to different management practices.
1b.Approach (from AD-416)
Work will be done on a cooperator farm that produces hybrid bermudagrass for hay during spring-summer and for grazing by beef cattle in fall-winter. Field plots are established in an existing stand of bermudagrass. Winter growth of any volunteer grass is suppressed. The plots are fertilized in spring using split applications of broiler litter (4 and 8 tons/acre), and a single application of 60 lbs N (34-0-0) at spring green up. Beginning in June and until the grass goes dormant, a 1-m center of each plot is harvested at two heights. Measurements are made of forage biomass and yield of 9 nutrient elements in the harvested hay. These same elements are determined in soil to 30-cm depth before spring fertilization and after fall dormancy. Statistical analysis focuses on the interaction of harvest interval and harvest height on yield of forage and nutrients. Nutrient uptake is compared for the two harvesting heights to determine if increased biomass production leads to proportional increases in nutrient removal, particularly N, P, K, Cu, and Zn. In subsequent years, plots will be sown to adapted cool-season forage crop to determine the rate of decline in soil nutrients when the rate of broiler litter is decreased or replaced with inorganic fertilizer.
Conducted research on the effectiveness of double-cropped forages to ameloriate soils with high phosphorus (P) concentration. Annual ryegrass was overseeded on dormant bermudagrass, which in the previous three years had received 4 and 8 tons broiler litter/acre. Starting in spring, nitrogen (N) fertilizer was applied at different times to favor the growth of ryegrass or both forage grasses. Soil nutrient concentration was determined at the end of the study. Measurements of soil inorganic N (nitrate and ammonia) are used to estimate the quantity of N escaping plant uptake. Intensive, year-round forage production appears to require attention to not only N nutrition, but also potassium (K). The ADODR monitored this project by discussions with the principal scientist, who had frequent contact with the cooperator.