ARS | Publication request: Protecting water quality by developing subsurface application technology for dry manures

Submitted to: International Conference on Diffuse Pollution
Publication Type: Abstract Only
Publication Acceptance Date: May 17, 2010
Publication Date: September 12, 2010
Citation: Pote, D.H., Way, T.R., Kleinman, P.J., Moore Jr, P.A., Sistani, K.R. 2010. Protecting water quality by developing subsurface application technology for dry manures [abstract]. International Conference on Diffuse Pollution. Page 217.

Technical Abstract: Animal manure provides a rich source of crop nutrients, but applying manure on the soil surface can result in significant nutrient losses that degrade water quality and accelerate the eutrophication process. Because surface-applied manure is completely exposed to the atmosphere, runoff water can transport phosphorus, nitrogen, and other manure nutrients into streams, lakes, estuaries, and bays; and much of the ammonia nitrogen volatilizes into the atmosphere before it can enter the soil. For tilled cropping systems, incorporating manure into the soil has proven to be a successful technique for decreasing nutrient losses and odors, but existing farm implements have not been capable of applying dry manures, such as poultry litter under the surface of perennial pastures and other no-till systems. Our goal was to develop management options that allow no-till producers to decrease nutrient losses from dry manure applications, thus protecting air and water quality while increasing soil productivity. Field plots were established to test the hypothesis, that nutrient losses could be decreased by applying dry poultry litter in shallow (8-cm deep) trenches beneath the surface of perennial grassland. Results showed that subsurface litter application decreased nutrient losses in runoff more than 90% compared to those from surface-applied litter, and prevented the volatilization of ammonia-N. In fact, nutrient losses from subsurface litter were statistically as low as those from plots receiving no litter. Furthermore, subsurface-applied litter produced greater forage yields than surface-applied litter, possibly by retaining more N in the soil. With these encouraging results, research efforts were initiated to make subsurface litter application a practical management option for no-till producers by fully mechanizing the technique. Single-shank and four-shank prototypes were developed, and successfully placed dry poultry litter under the surface of rocky perennial pasture and other no-till systems, but these prototypes had limited capacity and litter distribution capabilities. Therefore, a research team at the Dale Bumper Small Farms Research Center designed and constructed a larger (eight shanks, each equipped with a double-disk trench opener) tractor-drawn prototype, that can transport five tons of dry untreated litter directly from the poultry house and rapidly apply it under the surface of no-till fields at the desired rate. Known as the 'Poultry Litter Subsurfer', this prototype machine provides more precise control of dry manure application rates, including uniform distribution and very low rates that are not feasible when using conventional manure spreaders. Initial field testing indicates the Subsurfer can prevent most losses of phosphorus, nitrogen, and other nutrients that occur in surface runoff when poultry litter is applied to agricultural fields by conventional surface-broadcast methods.