AMMONIA VOLATILIZATION FROM SURFACE-APPLIED, FRESH AND COMPOSTED POULTRY LITTER

Poultry litter is a mixture of excreta, bedding material, and waste feed, which is generated in large amounts by the poultry industry. This material is usually applied to pastures as fertilizer. Application of poultry litter on the soil surface can lead to high NH3 volatilization losses due in part to a high rate of N mineralization. Composted poultry litter has a lower rate of N mineralization than fresh poultry litter and, therefore, should show lower NH3 losses. The first objective of this work was to compare N mineralized and NH3 volatilized from fresh and composted poultry litter applied on the soil surface. When poultry litter is applied to pastures, a fraction of the material falls on top of a thatch layer, which prevents direct contact with the soil and may, therefore, affect NH3 volatilization. The second objective of this work was to evaluate the effect of a thatch layer on N mineralized and NH3 volatilized from surface-applied, fresh poultry litter. Moist samples from two soils were packed in acrylic cylinders to achieve 55% water-filled-porosity. Two composted litters were applied on the soil surface and fresh poultry litter was applied either directly on the soil surface or on a thatch layer. All samples were incubated at 25 degrees C for 56 days, with NH3 volatilized measured during the first 21 days. Cumulative NH3 losses in 21 days ranged form 17 to 31% of the applied N for fresh poultry litter, and from 0 to 0.24% of the applied N for composted poultry litter. Application of fresh poultry litter on fescue thatch reduced the initial rate of NH3 volatilization but did not affect the total amount of NH3 volatilized in 21 days.