title: The effects of soil carbon on phosphorus and sediment loss from soil trays by overland flow.
abstract: Soil chemical constituents influence soil structure and erosion potential. We investigated manure and inorganic fertilizer applications on soil chemistry (carbon [C] quality and exchangeable cations), aggregation, and phosphorus (P) loss in overland flow. Surface samples (0-5 cm) of a Hagerstown (fine, mixed, semiactive, mesic Typic Hapludalf) soil, to which either dairy or poultry manure or triple superphosphate had been applied (0-200 kg P ha(-1) yr(-1) for 5 yr), were packed in boxes (1 m long, 0.15 m wide, and 0.10 m deep) to field bulk density (1.2 g cm(-3)). Rainfall was applied (65 mm h(-1)), overland flow collected, and sediment and P loss determined. All amendments increased Mehlich 3-extractable P (19-177 mg kg(-1)) and exchangeable Ca (4.2-11.5 cmol kg(-1)) compared with untreated soil. For all treatments, sediment transport was inversely related to the degree of soil aggregation (determined as ratio of dispersed and undispersed clay; r = 0.51), exchangeable Ca (r = 0.59), and hydrolyzable carbohydrate (r = 0.62). The loss of particulate P and total P in overland flow from soil treated with up to 50 kg P ha(-1) dairy manure (9.9 mg particulate phosphorus [PPI, 15.1 mg total phosphorus [TP]) was lower than untreated soil (13.3 mg PP, 18.1 mg TP), due to increased aggregation and decreased surface soil slaking attributed to added C in manure. Manure application at low rates (<50 kg P ha(-1)) imparts physical benefits to surface soil, which decrease P loss potential. However, at greater application rates, P transport is appreciably greater (26.9 mg PP, 29.5 mg TP) than from untreated soil (13.3 mg PP, 18.1 mg TP).
authors.affiliation: AgResearch Ltd., Invermay Agricultural Centre, Private Bag 50034, Mosgiel, New Zealand. richard.mcdowell@agresearch.co.nz
authors.forename: R W
authors.initials: RW
authors.lastname: McDowell
authors.forename: A N
authors.initials: AN
authors.lastname: Sharpley
mesh_terms: D002244:Carbon / Q000032:analysis / Q000737:chemistry*; D003247:Conservation of Natural Resources; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000737:chemistry*; D006813:Humidity; D007474:Ion Exchange; D008372:Manure; D010758:Phosphorus / Q000032:analysis / Q000737:chemistry*; D012987:Soil; D012995:Solubility; D014872:Water Movements
chemical_list: D008372:Manure; D012987:Soil; D010758:Phosphorus; D002244:Carbon