Leaching potential of phosphorus from cattle excreta patches in the central highlands of Florida.

ABSTRACT

Research is limited for cow-calf operations as a potential nonpoint source of P within Florida's central highlands region (CHR). The study was conducted in a bahiagrass ( Flügge) pasture. The soil is an excessively drained 'Candler' sand. In dung-designated plots, 2 kg of fresh cattle dung was deposited across the surface of a 15-cm-radius circular zone (Zone 1 [Z1]) centered within 3 × 3 m plots. In urine plots, 1 L of urine was deposited on Z1 and 1 L on Zone 2 (Z2), an area extending outward from Z1 to 30 cm from plot center. In dung and urine plots, Zone 3 (Z3) extended from Z2 to 45 cm from plot center and Zone 4 (Z4) from Z3 to 60 cm. Excreta deposition frequencies (DFs) were 0, 1, 2, and 3 times per year during 2006 and 2007. Total apparent remaining P (ARP = [fertilizer P + excreta P] - forage P removal) for Z1 of dung plots was 21, 447, 905, and 1249 kg ha for DF0, DF1, DF2, and DF3, respectively. In 2008, soil was incrementally sampled to a depth of 120 cm in all zones. Urine deposition did not increase soil P. Soil P levels and the degree of P saturation percentages increased with DF but only in the upper 10 cm of topsoil beneath Z1 of dung plots. Our results suggest that the risk of dung P reaching groundwater is low due to a considerable P retention capacity within the rooting zone of the Candler soil.