Soil Testing to Predict Dissolved Reactive Phosphorus Loss in Surface Runoff from Organic Soils.

Zheng, Z.M., Zhang, T.Q., Wen, G., Kessel, C., Tan, C.S., O'Halloran, I.P., Reid, D.K., Nemeth, D., and Speranzini, D. (2014). "Soil Testing to Predict Dissolved Reactive Phosphorus Loss in Surface Runoff from Organic Soils.", Soil Science Society of America Journal, 78(5), pp. 1786-1796. doi : 10.2136/sssaj2014.02.0065  Access to full text


Phosphorus loss from surface runoff contributes to eutrophication of surface water, a problem that is often severe from polders with organic soils where agricultural production is intensive. A soil P test is essential to predict the potential for P losses to precisely conduct environmental risk assessment and to efficiently develop and evaluate beneficial management practices. This study evaluated the possibility of using the environmental and agronomic soil P tests, soil P sorption index (PSI), and degree of soil P saturation (DPS), which are used for mineral soils, to predict surface runoff dissolved reactive P (DRP) from organic soils. Forty-four soils from eight subgroups representative of organic lands across Ontario were selected to provide a wide range of soil test P (STP) within each category. A surface runoff study was conducted following the U.S. National Phosphorus Research Project protocol. Flow-weighted mean runoff DRP cssoncentration (DRP30) was linearly related to soil water- and CaCl2–extractable P concentrations but with data distribution patterns that inefficiently represented the soil variability in P release potentials. The runoff DRP30 was significantly related to Bray-1 P and FeO-extractable P concentrations in split-line models, each with a change point, but not to Mehlich-3 P and Olsen P. All DPS values calculated based on STP and their derived PSIs were closely related to runoff DRP30 in either a linear or a split-line model. The DPS values expressed as Bray-1 P/(PSI + Bray-1 P) and FeO P/(PSI + FeO P) showed the highest correlation with runoff DRP30 and thus can be recommended as environmental risk indicators of surface runoff DRP from organic soils.

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