title: Seasonal exports of phosphorus from intensively fertilised nested grassland catchments.
abstract: We carried out a one year (2002) study of phosphorus (P) loss from soil to water in three nested grassland catchments with known P input in chemical fertilizer and animal liquid slurry applications. Chemical fertilizer was applied to the grasslands between March and September and animal slurry was applied over the twelve months. The annual chemical P fertilizer applications for the 17 and 211 ha catchments were 16.4 and 23.7 kg P/ha respectively and the annual slurry applications were 10.7 and 14.0 kg P/ha, respectively. The annual total phosphorus (TP) export in stream-flow was 2.61, 2.48 and 1.61 kg P/ha for the 17, 211 and 1524 ha catchments, respectively, compared with a maximum permissible (by regulation) annual export of ca. 0.35 kg P/ha. The export rate (ratio of P export to P in land applications) was 9.6% and 6.6% from the 17 and 211 ha catchments, respectively. On average, 70% of stream flow and 85% of the P export occurred during the five wet months (October to February) indicating that when precipitation is much greater than evaporation, the hydrological conditions are most favourable for P export. However the soil quality and land use history may vary the results. Particulate P made up 22%, 43% and 37% of the TP export at the 17, 211 and 1524 ha catchment areas, respectively. As the chemical fertilizer was spread during the grass growth months (March to September), it has less immediate impact on stream water quality than the slurry applications. We also show that as the catchment scale increases, the P concentrations and P export decrease, confirming dilution due to increasing rural catchment size. In the longer term, the excess P from fertilizer maintains high soil P levels, an antecedent condition favourable to P loss from soil to water. This study confirms the significant negative water quality impact of excess P applications, particularly liquid animal slurry applications in wet winter months. The findings suggest that restricted P application in wet months can largely reduce the P losses from soil to water.
authors: Department of Civil and Environmental Engineering, University College Cork, Ireland. ciaran.lewis@gmail.com
authors: Ciaran
authors: C
authors: Lewis
authors: Department of Microbiology and Plant Biology, University of Oklahoma, Norman OK 73019, USA.
authors: Rashad
authors: R
authors: Rafique
authors: Department of Civil and Environmental Engineering, University College Cork, Ireland.
authors: Nelius
authors: N
authors: Foley
authors: Department of Civil and Environmental Engineering, University College Cork, Ireland.
authors: Paul
authors: P
authors: Leahy
authors: Aquatic Services Unit, Environmental Research Institute, University College Cork, Ireland.
authors: Gerard
authors: G
authors: Morgan
authors: Department of Civil and Environmental Engineering, Duke University, Durham, NC 27708, USA.
authors: John
authors: J
authors: Albertson
authors: Department of Plant Science, South Dakota State University, Brookings, SD 57007, USA.
authors: Sandeep
authors: S
authors: Kumar
authors: Department of Civil and Environmental Engineering, University College Cork, Ireland.
authors: Gerard
authors: G
authors: Kiely
mesh_terms: D017753:Ecosystem; D004784:Environmental Monitoring; D005308:Fertilizers; D010758:Phosphorus / Q000032:analysis*; D006109:Poaceae; D012621:Seasons
chemical_list: D005308:Fertilizers; D010758:Phosphorus