See more from this Session: Symposium--State of Animal Manure and Onsite Septic Systems Wastewater Management On Water Resources and Environment. Part II
Wednesday, October 19, 2011: 2:20 PM
Henry Gonzalez Convention Center, Room 217B, Concourse Level
Livestock manure can supply essential crop nutrients and contribute to improved soil quality. However, conventional surface broadcast application can result in adverse environmental effects from NH3 volatilization, odor, and runoff losses of nutrients and pathogens. Incorporation of manure by tillage or standard injection methods conserves N but can also reduce residue cover and increase erosion; and tillage is not an option for no-till crops and perennial forages. Several novel application methods incorporate or limit surface exposure of manure so that N is conserved but residue is maintained, resulting in environmental, nutrient availability, and crop quality benefits. In annual crops, low-disturbance coulter or sweep injection methods or a manure injection/zone tillage combination (“zone-jection”) incorporate liquid manure while maintaining residue. Sediment and P runoff loss is typically reduced, but actual effectiveness depends on specific equipment and soil conditions. Nitrate leaching effects vary and, in some cases, may increase due to an increased inorganic N pool (due to reduced NH3-N losses) and/or manure placement. Sidedressing manure into a growing crop with injectors or s-tine cultivators provides available N at an optimum time and can decrease nutrient runoff. In perennial grass forages, surface banding of liquid dairy or swine manure with a trailing-foot technique has shown increased N utilization and forage yields and NH3-N volatilization reductions of 30 to over 50% compared to broadcast application. Application by shallow injection is the most effective in reducing odor and ammonia emission but has the potential to damage the sward. A technique that applies surface-bands of slurry over aeration slots provide greater NH3-N loss reduction than surface banding alone, while increasing N utilization and decreasing odor and N and P runoff losses. By reducing N losses all of these techniques improve the manure N:P balance for most crops, thereby reducing excessive P application (N-based application) or decreasing need for fertilizer N (P-based application). These improved manure application methods provide agronomic and/or environmental benefits compared to conventional broadcast application.