Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/24/2013
Publication Date: 1/1/2014
Citation: Pote, D.H., Meisinger, J.J. 2014. Effect of poultry litter application method on ammonia volatilization from a conservation tillage system. Journal of Soil and Water Conservation. 69(1):17-25.
Interpretive Summary: Poultry litter is an excellent organic fertilizer, but the usual practice of spreading litter on the surface of farm fields allows much of the valuable litter nitrogen to evaporate as ammonia, a problem that is economically costly for farmers and can be harmful to soil and water quality. A research team at USDA's Agricultural Research Service developed new technology for applying poultry litter below the soil surface, and conducted replicated research trials to compare ammonia losses from three different litter application methods in a row-crop conservation tillage system. The researchers found that when they compared other application methods to traditional surface spreading of poultry litter, ammonia losses decreased an average of 67% when the litter received a light disking after surface application, and decreased an average of 88% when the litter was subsurface applied using the new technology. This study is of interest to extension personnel, scientists, agricultural producers, and the general public because the subsurface-application technology can provide an effective management option to help farmers improve economic returns by greatly reducing nitrogen losses in conservation tillage systems, increase nitrogen recovery in the following crop, and reduce potential losses to the environment.
Technical Abstract: Ammonia volatilization from agricultural fields is important economically as a direct loss of a valuable crop nutrient (nitrogen), but is also a serious environmental concern for soil and water quality. As poultry production has expanded in cropland areas of the southeastern United States, poultry litter has become a major source of crop nutrients for farmers using conservation tillage systems. However, the conventional application method of broadcasting poultry litter on the soil surface can allow as much as 60% of the applied litter N to volatilize as ammonia. To provide management options that can prevent ammonia losses and help farmers use poultry litter nutrients more efficiently, a research team at USDA's Agricultural Research Service developed a prototype tractor-drawn implement for subsurface application of dry poultry litter in conservation tillage systems. When compared to surface broadcasting, previous research showed that subsurface application of poultry litter decreased odor problems, increased crop yields, prevented more than 90% of nutrient losses in runoff, and prevented ammonia volatilization from perennial pasture systems. The current study was conducted to expand our knowledge regarding the effect of this litter application method on ammonia volatilization from row-crop conservation tillage systems. For two consecutive summers, field plots with a uniform high-residue surface cover of chopped wheat straw received about 5000 kg-1 ha-1 of poultry litter applied by: surface spreading with no incorporation, surface spreading followed by light disking, or subsurface banding using the prototype USDA-ARS applicator. Small mobile wind tunnels monitored ammonia volatilization for at least five days after each litter treatment. Results for both years showed that ammonia losses were consistently affected by diurnal variations that were closely related to the vapor pressure deficit. Compared to conventional surface spreading of poultry litter, ammonia volatilization decreased an average of 67% when the litter application was followed by light disking, and decreased an average of 88% when the litter was applied below the soil surface using the prototype applicator. These data show that subsurface injection of dry poultry litter can constrain ammonia losses to minimal levels, thus conserving nitrogen for row crops and reducing potential nitrogen losses to the environment.