NITROGEN TRANSFORMATIONS IN SURFACE-APPLIED POULTRY LITTER - EFFECT OF LITTER PHYSICAL CHARACTERISTICS

Passing poultry litter through a fine sieve (<0.83 mm) generates a fin e fraction that is higher in N concentration than the whole litter and cheaper to transport per unit of N. This fine fraction can be pelleti zed to facilitate handling, but changing the physical characteristics of the litter may change the amount of N loss or the rate at which N m ineralizes. The objective of this work was to evaluate the effect of p hysical characteristics of the fine poultry litter fraction (pelletize d or fine particles) on net N and C mineralization, NH3 volatilization , and denitrification resulting from surface applications of the fine fraction to Cecil loamy sand (clayey, kaolinitic, thermic Typic Kanhap ludult) and Dothan loamy sand (fine-loamy, siliceous, thermic Plinthic Kandiudulf) soils. The soils were adjusted to 52% water-filled porosi ty, treated with either pelletized or fine-particle poultry fitter at 30.7 g N m(-2), and incubated at 25 degrees C for 35 d. Humidified air was circulated over each sample (15 chamber volumes min(-1)) and the NH3 evolved was trapped in 0.025 M H2SO4. Inorganic N contents and rat es of denitrification and respiration were measured at 1, 3, 7, 14, 21 , and 35 d after application. The physical characteristics of the litt er did not affect total amounts of net N mineralized and NH3 voIatiliz ed in 35 d. However, total denitrification Losses were significantly h igher for pelletized (6.2% of the applied N in Dothan and 7.9% in Ceci l) than for fine-particle fitter (0.2% in Dothan and 0.8% in Cecil). T hus, surface application of pelletized litter may result in increased denitrification losses compared with fine particle litter.