title: [Contents and movement of phosphorus in soil of long term effluent irrigated land forest].
abstract: Treated sewage effluent from Rotorua City, New Zealand, has been spray-irrigated into Whakarewarewa Forest to minimize effluent-derived nitrogen (N) and phosphorus (P) entering Lake Rotorua. To assess the capacity of the ecosystem to assimilate the effluent derived nutrients, a long term field trial was established within the Rotorua land treatment system. The objective of this study was to determine the accumulation, redistribution and movement of P in the volcanic soil after 11 year effluent irrigation. The soil samples were analyzed. Soil pH, total phosphorus (TP), Olsen P, Mehlich-3 P(M3P), M3Ca and M3Mg had increased significantly (p < 0.05) in the top soil (0-10 cm) in all effluent treated plots compared with the control plots. Some significant increase had extended deeper soil layer (20-40cm) or much deeper soil layer. Most effluent-derived P had accumulated in top 40cm. Concentrations of soil Olsen P and M3P in the medium and high effluent treatments were over environmental threshold levels (Olsen P, 60 mg x kg(-1); M3P, 150 mg x kg(-1)) in the top 20 cm. The values of soil saturation ratio (M3PSR) show that it was nearly saturated of soil P sorption in top soil. It was suggested that there was a potential environment crisis for soil P to move downward with drainage water. Regular soil sampling and Olsen P measurement using 60 mg x kg(-1) as an environment threshold could provide a solution for monitoring the movement of P down the soil profile. Phosphorus saturation ratio index (M3PSR) calculated as the molar ratio of M3P to (M3Al + M3Fe) appeared to be inadequate as an indicator for downward movement of soil P in such land treatment system. A new Phosphorus saturation ratio index for this system will be one of future study work.
authors.affiliation: Department of Environmental Science and Engineering, Southwest Forestry College, Kunming 650224, China. hhr@swfc.edu.cn
authors.forename: Hui-rong
authors.initials: HR
authors.lastname: Hu
authors.forename: Hai-long
authors.initials: HL
authors.lastname: Wang
authors.forename: Kimberley
authors.initials: K
authors.lastname: Mark
mesh_terms: D057914:Agricultural Irrigation / Q000379:methods*; D005308:Fertilizers; D016468:Forestry / Q000379:methods; D010758:Phosphorus / Q000032:analysis* / Q000737:chemistry; D012989:Soil Pollutants / Q000032:analysis*; D014197:Trees / Q000254:growth & development*; D014865:Waste Disposal, Fluid / Q000379:methods*
chemical_list: D005308:Fertilizers; D012989:Soil Pollutants; D010758:Phosphorus