Effects of Subsurface Applying Poultry Litter in Pasture and No-till Systems.

Poultry litter provides a rich nutrient source for crops, but the usual practice of surface-broadcasting litter can degrade water quality by allowing storm runoff to transport nutrients into streams and lakes, while much of the ammonia-N escapes into the atmosphere. We developed and tested a knifing technique to decrease nutrient losses while increasing soil productivity by directly applying dry poultry litter beneath the surface of pastures and other no-till systems. Results showed that subsurface application of litter decreased ammonia-N volatilization and nutrient losses in runoff more than 90% (compared to surface-applied litter), to levels statistically as low as those from control (no litter) plots. Given this success, two advanced tractor-drawn prototypes were developed to subsurface apply poultry litter in field research. The two prototypes have been tested in pasture and/or no-till experiments, and are both effective in improving nutrient-use efficiency compared to surface-applied litter, increasing crop yields (possibly by retaining more nitrogen in the soil), and decreasing nutrient losses, often to near background (control plot) levels. A paired-watershed study showed that cumulative phosphorus losses in runoff from continuously-grazed perennial pastures were decreased by 55% over a three-year period if the annual poultry litter applications were subsurface applied rather than surface broadcast.