(Georgia Institute of Technology, 1999-03)
Kuykendall, Holli; Cabrera, Miguel L.; Hoveland, Carl; McCann, Mark; West, Larry
Repeated heavy applications of broadcast broiler litter can increase nutrient nmoff from pastures. Rotational stocking of cattle, as compared to continuous stocking, may be useful in decreasing surface nutrient runoff because of better manure . distribution and more uniform forage accumulation to act as filters and trap nutrients. The objective of this study was to measure phosphorus runoff from six 0.75- ha (6-8% slope) endophyte-infected tall fescuecommon bermudagrass pastures that were fertilized with 13 to 15 Mg (dry weight) ha-1 yr-1 broiler litter. Runoff was analyzed for dissolved reactive P (DRP) and total Kjeldahl P (TKP). Grazing method had no effect (P>0.10) on surface runoff quality or quantity. The average flow weighted concentration of DRP for both stocking treatments was 5.1 mg P L-1 for the first year and 8.2 mg P L-1 for the second year {P<0.10). The flow weighted concentration of TKP was 6.8 mg P L-1 for the first year and 12.8 mg P L-1 for the second year (P<0.10). A substantial portion of the second year nutrient loss came from a single runoff event that occurred just two days after the third broiler litter application.
(Georgia Institute of Technology, 1999-03)
Kuykendall, Holli; Hoveland, Carl; McCann, Mark; Cabrera, Miguel L.
Previous research has shown that surface application of broiler litter to pastures can lead to elevated concentrations of dissolved reactive phosphorus (DRP) in surface runoff. It is not clear, however, for how long a after broiler litter application DRP concentrations in runoff remain high. This work was conducted to study the evolution of DRP concentration in surface runoff from pastures that received broiler litter in 1995 and 1996, and only inorganic fertilizer Nin 1997 and 1998. The results showed that DRP concentrations in surface runoff remained high (> 2 mg P L-1) while broiler litter was being applied. Once broiler litter applications stopped, DRP concentrations in runoff decreased below 1 mg p L-1 within 19 months. These results suggest that the risk of contaminating surface waters with DRP could be decreased by fertilizing pastures with broiler litter every two or three years, with the addition of only fertilizer N in those years when broiler litter is not applied.