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

Poultry litter is a mixture of excreta, bedding material, and waste fe ed, 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 poul try litter has a lower rate of N mineralization than fresh poultry lit ter and, therefore, should show lower NH3 losses. The first objective of this work was to compare N mineralized and NH3 volatilized from fre sh and composted poultry litter applied on the soil surface. When poul try litter is applied to pastures, a fraction of the material falls on top of a thatch layer, which prevents direct contact with the soil an d may, therefore, affect NH3 volatilization. The second objective of t his 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 soi l surface and fresh poultry litter was applied either directly on the soil surface or on a thatch layer. All samples were incubated at 25 de grees 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 a pplied 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.