Submitted to: Environmental Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 8, 2009
Publication Date: July 7, 2009
Citation: Pote, D.H., Way, T.R., Sistani, K.R., Moore Jr, P.A. 2009. Water-quality effects of a mechanized subsurface-banding technique for applying poultry litter to perennial grassland. Journal of Environmental Management. 90(11):3534-3539. Interpretive Summary: Poultry litter is an excellent source of crop nutrients, but the common practice of spreading litter on the field surface allows valuable nutrients to evaporate or be carried by storm runoff water into nearby streams and lakes. Research has shown that applying the litter in shallow trenches (bands) below the soil surface can prevent most nutrient losses with very little disturbance of the soil structure or plant roots; yet this technique has only been tested manually, so a follow-up study was conducted to evaluate a mechanized version of the subsurface-banding technique. This study showed that compared to spreading litter on the surface, mechanized subsurface application of litter decreased nutrient losses by more than 90 percent and tended to increase forage yield and quality. The study is of interest to scientists, extension personnel, agricultural producers, and the general public because this method of applying litter below the surface of permanent pastures could potentially lead to higher forage yield and quality on millions of acres, while also improving air and water quality.
Technical Abstract: Poultry litter is known to be an excellent organic fertilizer, but the common practice of spreading litter on the surface of pastures has raised serious water-quality concerns and may limit potential benefits of poultry litter applications. Because surface-applied litter is completely exposed to the atmosphere, runoff can transport nutrients into nearby streams and lakes, and much of the ammonium nitrogen volatilizes before it can enter the soil. Our previous research showed that a manual knifing technique to apply dry litter under a perennial pasture surface effectively prevented about 90 percent of nutrient losses in runoff from surface-applied litter, and tended to increase forage yield. However, this technique (known as subsurface banding) can not become a practical management option for producers until it is mechanized. To begin that process, we tested an experimental single-shank, tractor-drawn implement designed to apply poultry litter in subsurface bands. Our objective was to compare this mechanized subsurface banding method against conventional surface application to determine effects on nutrient losses in runoff from perennial grassland treated with dry poultry litter. Early in the growing season, broiler litter was applied (6.7 dry-weight Mg ha -1) to each plot (except three control plots) using one of two application methods: surface broadcast manually or subsurface banded using the tractor-drawn implement. Treatments were randomly assigned to plots, with three replications. Simulated rainfall (5 cm h -1) generated 20 min of runoff from each plot for volume and analytical measurements. Results showed that the mechanized method of applying poultry litter in subsurface bands increased forage yield while decreasing nutrient losses in runoff at least 90 percent compared to surface-broadcast litter.