Water-quality effects of a mechanized subsurface-banding technique for applying poultry litter to perennial grassland

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 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% of nutrient loss with runoff from surface-applied litter, and tended to increase forage yield. However, this technique (known as subsurface banding) cannot 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 loss with runoff from a 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. Simulated rainfall (5 cm h⁻¹) generated 20 min of runoff from each plot for volume and analytical measurements. Results showed that subsurface-banded litter increased forage yield while decreasing nutrient (e.g. N and P) loss in runoff by at least 90% compared to surface-broadcast litter.