Comparing measures for determination of phosphorus saturation as a method to estimate dissolved P in soil solution

Authors: BLOMBACK, KARIN - Swedish University Of Agricultural Sciences; Bolster, Carl; LINDSJO, ANDERS - Swedish University Of Agricultural Sciences; HESSE, KATHRIN - Swedish University Of Agricultural Sciences; LINEFUR, HELENA - Swedish University Of Agricultural Sciences; PARVAGE, MASUD - Swedish University Of Agricultural Sciences

Submitted to: Geoderma
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/2/2020
Publication Date: 9/18/2020
Citation: Blomback, K., Bolster, C.H., Lindsjo, A., Hesse, K., Linefur, H., Parvage, M. 2020. Comparing measures for determination of phosphorus saturation as a method to estimate dissolved P in soil solution. Geoderma. 383. https://doi.org/10.1016/j.geoderma.2020.114708.
DOI: https://doi.org/10.1016/j.geoderma.2020.114708

Interpretive Summary: Phosphorus loadings from agricultural fields can increase eutrophication rates in surface waters thereby negatively impacting water quality. A significant source of phosphorus in agricultural soils is phosphorus sorbed to soil, thus it is important to evaluate the risk of phosphorus being released from soils. The ratio of sorbed phosphorus to maximum phosphorus sorption capacity of a soil has been shown to be a good predictor of a soil’s risk of releasing P in runoff or leaching water. However, different soil extraction methods give different values for this ratio. In this study we compare different extraction methods for computing the degree of phosphorus saturation of a soil and evaluate each method against data measuring easily dissolved soil phosphorus in solution. Our results suggest that there are multiple DPS metrics that provide similar predictions for evaluating a soil’s potential for releasing sorbed P into solution. Taking into account the availability of data, DPS established from standard soils tests using ammonium lactate extractions appears to be a promising and useful empirical tool to identify high risk soils in Sweden.

Technical Abstract: In response to concerns over the translocation of P from soils to P-sensitive water bodies, there is high demand for developing simple indicators for evaluating a soil’s risk of releasing P into solution. The objective of this study was to investigate the accuracy of different approaches for calculating the degree of P saturation (DPS) to predict concentrations of dissolved P in soil for a wide range of Swedish arable soils. Correlations between different soil P extractions, estimates of P sorption capacities (PSC) and measures of DPS were investigated. Our results suggest that there are multiple DPS metrics that provide similar predictions for evaluating a soil’s potential for releasing sorbed P into solution. Taking into account the availability of data, DPS established from standard soils tests using ammonium lactate extractions appears to be a promising and useful empirical tool to identify high risk soils in Sweden.