Modeling phosphorus concentrations in Irish rivers using land use, soil type, and soil phosphorus data.
Modeling diffuse phosphorus (P) loss may indicate management strategies to minimize P loss from agricultural sources. An empirical model predicting flow-weighted phosphorus concentrations (MRP) was derived using data collected from 35 Irish river catchments. Monitoring records of riverine P and stream flow data were used to calculate MRP values averaged for the years 1991-1994. These data were modeled using land use, soil type, and soil P data. Soil type in catchments was described using soil survey classifications weighted according to their P desorption properties from laboratory results. Soil test P concentrations for the studied watersheds were obtained from a national database. Soil P levels were weighted based on the results of field experiments measuring P losses in overland flow from fields at different soil test P levels. The 35 catchments were statistically clustered into two populations (A and B) based on differences in soil type, specifically, soil hydrology. Catchments in Cluster A had predominantly poorly drained soils and comparatively higher MRP concentrations (0.03-0.17 mg L(-1)) than Cluster B areas (0.01-0.7 mg L(-1)) with mostly well-drained soils. Regression equations derived for A and B type catchments predicted MRP values with 68 and 62% of the variation explained in the models, respectively. Data extracted for the rest of the country were applied to the models to delineate areas at risk on a national scale. While the models were only moderately accurate they highlighted the influence of land management, specifically, high production grassland receiving high P inputs, in conjunction with the effect of soil type and soil hydrology on the transport of P to surface waters.
Daly
Karen
K
Johnstown Castle Research Centre, Wexford, Ireland. kdaly@johnstown.teagasc.ie
Mills
Paul
P
Coulter
Brian
B
McGarrigle
Martin
M
D000383:Agriculture; D004777:Environment; D005308:Fertilizers; D005544:Forecasting; D007494:Ireland; D008962:Models, Theoretical; D010758:Phosphorus / Q000032:analysis*; D006109:Poaceae; D012680:Sensitivity and Specificity; D012989:Soil Pollutants / Q000032:analysis*; D014872:Water Movements; D014873:Water Pollutants / Q000032:analysis*
D005308:Fertilizers; D012989:Soil Pollutants; D014873:Water Pollutants; D010758:Phosphorus