Phosphorus in Runoff and Leaching Potentially Mitigated by Biochar Application in Agricultural Fields.

Dissolved and particulate phosphorus (P) leaching and runoff from agricultural soil poses an environmental risk to nearby watercourses. Biochar, a carbon-rich soil amendment made from pyrolysed biomass, may reduce P leaching and runoff rates by altering the physical and chemical soil properties. Two experiments were conducted on biochar-amended soils to assess the dissolved and particulate P concentrations in (1) simulated runoff (in-field experiment) and (2) leachate from repacked soil columns (laboratory experiment).  Soils were collected from an on-farm experiment in Ste-François-Xavier-de-Brompton, Quebec (Canada). Two years earlier, agronomic plots were amended with three types of biochar at 5, and 10 Mg/ha with one control, in a randomized complete block design, with 3 replicates. Two 30-minute rainfall simulations were done using the Cornell Sprinkle Infiltrometer. The runoff was collected 5 times (every 6 minutes) and analyzed for ortho-P, dissolved P, and particulate P. A column leaching experiment was conducted by collecting coarsely sieved soil (<6 mm mesh) and packing PVC columns (10.1 cm dia., 30 cm tall) to field bulk density (1.1 g cm^-3). Each column was leached with 8 pore volumes of water and the leachate is analyzed for ortho-P, dissolved P, and particulate P. Results will be presented.