MINERALIZABLE NITROGEN IN BROILER LITTER - II - EFFECT OF SELECTED SOIL CHARACTERISTICS

Broiler litter (BL) is a mixture of chicken (Gallus gallus domesticus) manure and bedding material that is commonly used as fertilizer for c rops and pastures. Knowledge of the factors that determine the amount of potentially mineralizable N in BL is needed to estimate adequate ap plication rates. Limited evidence suggests that soil characteristics s uch as texture can significantly affect the amounts of net N mineraliz ed from BL, This work was conducted to compare the kinetics of N miner alization of the same BL in nine different soil samples, and to determ ine the effect of selected soil characteristics on the amount and rate of decomposition of potentially mineralizable N in BL, Samples from t he same BL were mixed with nine soils (150 mg organic N kg(-1), -0.02 MPa) and incubated at 25 degrees C for 146 d, A two-pool, first-order kinetics model adequately described cumulative net N mineralized from the litter, which ranged from 364 to 784 g N kg(-1) organic N. Multipl e regression analysis generated statistically significant equations th at identified the ratio of (sand content/water content at field capaci ty) and pH as soil characteristics with a significant effect on the fa st and slow pools of mineralizable N. Combining a predictive equation for total mineralizable N based on BL characteristics with a predictiv e equation for total mineralizable N based on soil characteristics, we generated an equation that predicts total mineralizable N based on BL and soil characteristics. Future work should further test this equati on and correlate plant N uptake with predicted values of potentially m ineralizable N in BL.