FIELD-SCALE NITROGEN AND PHOSPHORUS LOSSES FROM HAYFIELDS RECEIVING FRESH AND COMPOSTED BROILER LITTER

Composting broiler litter may increase the amount of stable organic co mponents and reduce contamination of ground- and surface-water with N and P from excessive land applications. Limited research has been done comparing field-scale losses of nutrients from broiler litter applied to hayfields. This project determined field-scale N and P runoff loss es from fresh and composted litter applied to hayfields. Two rates of broiler litter, 10 Mg ha(-1) yr(-1) (1X) and 20 Mg ha(-1) yr(-1) (2X), and a mix of 10 Mg ha(-1) yr(-1) of broiler Litter and 50 Mg ha(-1) y r(-1) of composted litter (1X + C), were split-applied in April and Se ptember for 2 yr. Surface runoff and subsurface now were monitored for inorganic and total N and P. Nitrate concentrations in subsurface flo w remained below the USEPA standard of 10 mg L-1 for all treatments. A verage dissolved reactive P (DRP) concentrations were statistically hi gher under the 1X + C treatment, followed by the 2X and yi treatments, reaching a maximum of 8.5 mg L-1 under the 1X + C treatment. Differen ces between field and plot-scale results were most likely controlled b y the timing of application and occurrence of the first rainfall event . Concentrations of resin-extractable P (P-r) in soil increased under all treatments, indicating accumulation of P after only 2.5 yr Of appl ication. In this research, the amount of P applied was the principal d eterminant of the DRP concentration in the surface runoff. Composting broiler litter increased the amount of stable organic components.