Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/1999
Publication Date: N/A
Citation: Kleinman, P.J.A., Bryant, R.B., Reid, W.S. 1999. Development of pedotransfer functions to quantify phosphorus saturation of agricultural soils. Journal of Environmental Quality. 28:2026-2030. Interpretive Summary: The loss of phosphorus in runoff from agricultural lands is a major cause of accelerated eutrophication. Environmental indicators, however, such as soil phosphorus saturation, are not widely available as soil testing laboratories typically focus on agronomic soil analyses. To bridge the gap between agronomic and environmental soil analyses, this study offers one approach to estimating soil phosphorus saturation from agronomic soil test data. Results show that pedotransfer functions that include soil test phosphorus and aluminum are strongly correlated to phosphorus saturation. Thus, agronomic data may be used as surrogates for environmental data.
Technical Abstract: Soil P saturation affects the risk of P loss to surface and ground water and is therefore a critical environmental indicator in regions where eutrophication is a concern. In the USA, most soil testing laboratories do not include environmental indicators such as soil P saturation as standard soil test options. However, development of pedotransfer functions that relate soil test data to soil P saturation would enable soil testing laboratories to estimate soil P saturation as part of soil test results without significant additional expenditures. This study examines associations between readily-available soil test data (pH, soil organic matter and extractable P, Al, Fe, and Ca) and soil P saturation as estimated by acid ammonium oxalate extraction. Fifty-nine soil samples were collected from the Delaware River Watershed in New York State (42o21'N, 74o52'W) and subjected to standard soil test analyses as well as to acid ammonium oxalate extraction. Some soil test variables were well correlated with soil P saturation. As a single predictor, soil test P was most highly correlated to soil P saturation (r = 0.88). This association supports the use of soil test P as an environmental indicator. Soil test Al was also well correlated with soil P saturation following logarithmic transformation (r = 0.73). Multivariate pedotransfer functions containing soil test P, Al, Fe, soil organic matter and pH did not significantly improve estimation of soil P saturation (r = 0.91) above soil test P alone.