Introduction1 Broiler litter is a by-product of broiler production and consists of poultry excreta, feathers, wasted feed, and bedding material (Moore et al. 1995). Bosch and Napit (1992) concluded that the use of broiler litter as a nutrient source is an economical alternative to commercial fertilizers. Broiler litter contains high concentrations of water-soluble phosphorus, and generally much of the litter is broadcast to fields close to the production facility. Well-established pastures usually have a thatch layer that may reduce the contact between litter and soil, thereby reducing phosphorus absorption by the soil. Consequently, the presence of a thatch layer may lead to high concentrations of water soluble phosphorus on the soil surface, which in turn may increase the risk of surface water contamination with Phosphorus. Normally, the pastures have a significant amount of thatch. The broiler litter may persist in the soil surface for a long time when broiler litter was surface applied to pasture, and extending to the occurrence of rainfall and runoff. However, it is not clear that the dynamic of water-soluble P on the soil surface, and in the top 1 cm soil of pastures fertilized with broiler litter, and how that is affected by the presence of the thatch layer. A few studies have investigated P runoff losses from pasture applied broiler litter (Edwards and Daniel 1992, 1993, 1994; Heathman et al. 1995; Nichols et al. 1994; Shreve et al. 1995; Vervoort et al. 1998; Kuykendall et al. 1999). The parameters included soil characteristics, slop, and tillage, timing, quantity, and method of application of fertilizers, and intensity, quantity, and timing of rainfall. The results showed that the majority of P in runoff from poultry litter was soluble, and suggested that most effective practices to lessen the impact of poultry litter on water quality should focus on reducing soluble P losses (Edwards et al. 1996). This study was conducted to evaluate the effect of a thatch layer on the dynamics of water soluble P on the soil surface and in the upper soil of 1 cm in depth in undisturbed cores taken from a pasture. Materials and methods Four treatments were set to study the effect of thatch on water-soluble P in pastures fertilized with broiler litter. The treatments were: a) Control, soil without thatch. b) Soil with thatch. c) Soil without thatch plus broiler litter. d) Soil with thatch plus broiler litter. The rate of broiler litter applied was equal to 5 t穐m-2. The acrylic cylinder (4.4 cm diameter, 10 cm high) was used to sample undisturbed soil core with or without thatch. The soil cores were sampled from a fescue-bermudagrass pasture. Cylinders were placed into incubator at 25 oC for 8 weeks. Three cylinders for each treatment were sampled on specified days: 1, 3, 7, 14, 28, and 56. The upper soil of 1 cm in depth and top layer of thatch, litter, or both were sampled and extracted by deionized water at the water-to-litter ratio 200:1. Blinds were shaken at 120 opm for 4 hours then were centrifuged at 5000 revolutions for 5 min to separate solids. Supernatant solution was filtered through a 0.45 祄 filter. Phosphorus was determined by the molybdate-blue procedure. Results and discussion Effect of thatch on dynamic of water-soluble P in upper soil of 1 cm in depth The contents of water soluble P in upper 1 cm soil showed a rapid increase during the first week after broiler litter was fertilized, followed by a slower increase for 3 weeks and reached the stable top under the treatment without thatch. Whereas, the contents of water soluble P under the treatments without broiler litter, no matter with or without thatch, showed a stable fluctuation from 1.2-2.4 kg穐m-2 during the whole 8-week incubation period (Fig. 1). The dynamic of water-soluble P contents fertilized with broiler litter were of significant difference between the treatments without thatch and with thatch. The contents of water-soluble P of no thatch treatment
More abstracts about the 草甸层对施用仔鸡废弃物牧场土壤中水溶性磷的影响(英文)