The effect of soil phosphorus on particulate phosphorus in land runoff

Authors: Withers; Hartikainen¹; Barberis²; Flynn³; Warren³

Source: European Journal of Soil Science, Volume 60, Number 6, December 2009 , pp. 994-1004(11)

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Accumulation of surplus phosphorus (P) in the soil and the resulting increased transport of P in land runoff contribute to freshwater eutrophication. The effects of increasing soil P (19-194 mg Olsen-P (OP) kg⁻¹) on the concentrations of particulate P (PP), and sorption properties (Q_max, k and EPCo) of suspended solids (SS) in overland flow from 15 unreplicated field plots established on a dispersive arable soil were measured over three monitoring periods under natural rainfall. Concentrations of PP in plot runoff increased linearly at a rate of 2.6 μg litre⁻¹ per mg OP kg⁻¹ of soil, but this rate was approximately 50% of the rate of increase in dissolved P (< 0.45 μm). Concentrations of SS in runoff were similar across all plots and contained a greater P sorption capacity (mean + 57%) than the soil because of enrichment with fine silt and clay (0.45-20 μm). As soil P increased, the P enrichment ratio of the SS declined exponentially, and the values of P saturation (P_sat; 15-42%) and equilibrium P concentration (EPCo; 0.7-5.5 mg litre⁻¹) in the SS fell within narrower ranges compared with the soils (6-74% and 0.1-10 mg litre⁻¹, respectively). When OP was < 100 mg kg⁻¹, P_sat and EPCo values in the SS were smaller than those in the soil and vice-versa, suggesting that eroding particles from soils with both average and high P fertility would release P on entering the local (Rosemaund) stream. Increasing soil OP from average to high P fertility increased the P content of the SS by approximately 10%, but had no significant (P > 0.05) effect on the P_sat, or EPCo, of the SS. Management options to reduce soil P status as a means of reducing P losses in land runoff and minimizing eutrophication risk may therefore have more limited effect than is currently assumed in catchment management.

Document Type: Research article

DOI: http://dx.doi.org/10.1111/j.1365-2389.2009.01161.x

Affiliations: 1: Department of Applied Chemistry and Applied Microbiology, University of Helsinki, PO Box 27, Latokartanonkaari, 00014 Helsinki, Finland 2: DIVAPRA, University of Torino, Via Leonardo Da Vinci 44, Grugliasco, 10095 Torino, Italy 3: Aquatic Environment Research Centre, Department of Geography, Whiteknights, University of Reading, PO Box 227, Reading, RG6 6AB, UK

Publication date: 2009-12-01

The effect of soil phosphorus on particulate phosphorus in land runoff

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