Submitted to: Nutrient Cycling in Agroecosystems
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/20/2013
Publication Date: 8/24/2013
Citation: Svanback, A., Ulen, B., Etana, A., Bergstrom, L., Kleinman, P.J., Mattsson, L. 2013. Influence of soil phosphorus and manure on phosphorus leaching in Swedish topsoils. Nutrient Cycling in Agroecosystems. 96:133–147. DOI:10.1007/s10705-013-9582-9. Interpretive Summary: In Sweden, losses of agricultural phosphorus via subsurface flow pathways are a major concern due to eutrophication of the Baltic Sea. Using shallow soil columns collected from trials across Sweden, this study sought to quantify relationships between subsurface phosphorus loss and key agronomic management factors. Soil phosphorus exerted an overwhelming control leaching losses of phosphorus, pointing to the need for strategies that balance phosphorus inputs and outputs to agricultural soils.
Technical Abstract: In Sweden, subsurface transport of phosphorus (P) represents the primary pathway of concern to surface water quality. While strong relationships have been consistently observed between P in surface runoff and soil test P, there have been mixed findings linking P in leachate with soil test P. To explore the interactive effects of soil, cropping system and manure application on P leaching, we obtained intact columns of surface soils (20 cm deep) from long-term trials across Sweden, subjecting the columns to leaching experiments using rainfall simulation. Strong relationships between ammonium-lactate extractable P and dissolved reactive P concentrations in leachate were observed, although regressions varied across soils. Results contrast with previous work in Sweden examining deeper soil cores (1.18 m) in which no relationship was apparent, pointing to the modifying role of subsoil properties for P leaching. No general differences in P leaching were found between the two cropping systems with and without moderate manure applications. The application of dairy manure (21-30 kg P/ha) to soils significantly increased P leaching losses, although the effect was modified by soil P sorption saturation. Both load (mg) and concentration (mg/L) of leached P can increase with increasing soil test P, strengthening the importance of keeping soil test P at moderate levels. Phosphorus leaching was generally low at fertilization rates equivalent to P removal with harvest. Findings point to the need for long-term P balances of inputs and outputs to limit P losses via leaching.