Abstract

Agriculture is one of the largest anthropogenic contributors of phosphorus (P) to surface waters and reducing these P loads is a target set by many countries. One potential mitigation strategy could be to utilize biochar, functionalized by co-precipitating metal ions onto its surface to adsorb phosphates. We evaluated such an approach in a series of laboratory experiments and a three-year field lysimeter study. Leached phosphates were trapped in a 3-cm layer of a commercially available 20% hardwood/80% Norway spruce biochar, coated with magnetite and placed under the soil root zone. Langmuir maximum adsorption potential (Qmax) was 3.38 mg P g(-1) biochar, as determined from batch adsorption studies performed at pH 6.5. Further laboratory experiments revealed that adsorption was strongly negatively correlated with pH (R-2 = 0.995). In a laboratory column study using high flow rates, no difference was found in phosphate adsorption between coated biochar and the control (no biochar), after application of ammonium phosphate at a rate corresponding to 22 kg P ha(-1). However, differences were observed at higher application rates (285 or 570 kg P ha(-1)). Calculation of a Fe:P molar ratio to evaluate the magnetite treatment method from laboratory (2:1) to lysimeter (248:1) suggested a relatively effective laboratory performance, but overall poor field efficiency. Nevertheless, biochar in the lysimeter study still reduced phosphate leaching from two organic soils, by 62% (P < 0.05) and 35% (NS). This suggests that, even though the method of magnetite-coating biochar is not necessarily resource-efficient, it is effective in removing P from soil leachate.

Keywords

Biochar; Leaching; Lysimeter; Magnetite; Phosphorus; Soil

Published in

Geoderma
2018, Volume: 327, pages: 45-54

SLU Authors

• Riddle, Matthew

  • Department of Soil and Environment, Swedish University of Agricultural Sciences
    

• Cederlund, Harald

  • Department of Molecular Sciences, Swedish University of Agricultural Sciences
    

• Schmieder, Frank

  • Department of Soil and Environment, Swedish University of Agricultural Sciences
    

• Bergström, Lars

  • Department of Soil and Environment, Swedish University of Agricultural Sciences
    

Sustainable Development Goals

Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation


UKÄ Subject classification

Soil Science
Environmental Sciences related to Agriculture and Land-use
Environmental Management


Publication identifier

DOI: https://doi.org/10.1016/j.geoderma.2018.04.025

Permanent link to this page (URI)

https://res.slu.se/id/publ/95490