title: Rainfall intensity and phosphorus source effects on phosphorus transport in surface runoff from soil trays.
abstract: Phosphorus runoff from agricultural fields amended with mineral fertilizers and manures has been linked to freshwater eutrophication. A rainfall simulation study was conducted to evaluate the effects of different rainfall intensities and P sources differing in water soluble P (WSP) concentration on P transport in runoff from soil trays packed with a Berks loam and grassed with annual ryegrass (Lolium multiflorum Lam.). Triple superphosphate (TSP; 79% WSP), low-grade super single phosphate (LGSSP; 50% WSP), North Carolina rock phosphate (NCRP; 0.5% WSP) and swine manure (SM; 70% WSP), were broadcast (100 kg total P ha-1) and rainfall applied at 25, 50 and 75 mm h-1 1, 7, 21, and 56 days after P source application. The concentration of dissolved reactive (DRP), particulate (PP), and total P (TP) was significantly (P<0.01) greater in runoff with a rainfall intensity of 75 than 25 mm h-1 for all P sources. Further, runoff DRP increased as P source WSP increased, with runoff from a 50 mm h-1 rain 1 day after source application having a DRP concentration of 0.25 mg L-1 for NCRP and 28.21 mg L-1 for TSP. In contrast, the proportion of runoff TP as PP was greater with low (39% PP for NCRP) than high WSP sources (4% PP for TSP) averaged for all rainfall intensities. The increased PP transport is attributed to the detachment and transport of undissolved P source particles during runoff. These results show that P source water solubility and rainfall intensity can influence P transport in runoff, which is important in evaluating the long-term risks of P source application on P transport in surface runoff.
authors.affiliation: Departamento de Ciência do Solo, ESALQ, University of São Paulo, Piracicaba, SP, Brazil.
authors.forename: Francirose
authors.initials: F
authors.lastname: Shigaki
authors.forename: Andrew
authors.initials: A
authors.lastname: Sharpley
authors.forename: Luis Ignacio
authors.initials: LI
authors.lastname: Prochnow
mesh_terms: D005308:Fertilizers; D010758:Phosphorus / Q000032:analysis*; D011891:Rain; D012989:Soil Pollutants / Q000032:analysis*; D014872:Water Movements
chemical_list: D005308:Fertilizers; D012989:Soil Pollutants; D010758:Phosphorus