2011 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.
Field studies were conducted with ryegrass-bermudagrass on a manure-impacted soil to complete final year of a two-year project (2008-09) on year-round forage production to ameliorate high soil phosphorus (P). Plots of bermudagrass were overseeded in autumn, nitrogen (N) fertilizer was applied in spring to stimulate mainly ryegrass, soils were sampled for residual N, and forage was harvested to determine species and total yield and P removal. The main-plot treatment was two antecedent rates of poultry litter, 8.96 and 17.92 Mg ha-1 (applied in spring 2005–2007), and the sub-plot treatment comprised six N fertilizer regimes and a ‘check’ plot (the same plot as in the previous study) that was not overseeded with ryegrass. The data were analyzed statistically and results are being summarized in a manuscript. In summer 2009, a disease was noted on leaves of ‘Tifton 44’ bermudagrass and crabgrass (Digitaria sp.) that markedly reduced forage yield in all test plots. Symptoms included brown to purple lesions and necrosis of the leaf tip. The greatest average decrease in forage yield was recorded from N regime #6 at 722 Kg/ha for the month of July harvests of 2009 minus 2008. Potassium (K) differences in tissue from 2008 to 2009 were all negative when comparing data taken in 2009 minus 2008 of July samples. Therefore, a follow-up study was conducted in 2010 to determine the effects of K fertilization on bermudagrass K status, which was depressed (< 1.7% dry weight basis) after double-cropping with ryegrass and providing N fertilizer only. Disease ratings and leaf samples were taken in September and October 2010. In cooperation with unit Plant Pathologist, we confirmed the occurrence and severity of six fungal pathogens involved in leaf blight during late-season. The identities of pathogens present in diseased leaves were determined for all 56 plots in the study, and these comprised varying percentages of six species of “Helminthosporium-type” fungi. Relationships between the occurrence and frequency of these individual pathogens, levels of disease severity, antecedent poultry litter treatments, and K concentrations in bermudagrass leaves are being analyzed statistically. Overall, disease incidence was approximately 10-20% greater in plants with low K nutrition status. The ADODR monitored this project with discussions with the principal scientist involved in this research. Principal scientist has frequent contact with the cooperator.