Effect of Wood Biochar in Manure-Applied Sand Columns on Leachate Quality

Agricultural operations can pose a threat to the quality of nearby water sources particularly from nitrogen (N) and phosphorus (P) losses following land application of manure. Biochar application to soils has the potential to ameliorate degraded soils and reduce nutrient leaching to groundwater. The effects of amending sand soil columns with hybrid poplar biochar (Populus spp.) made by a slow-pyrolysis process at 450 degrees C at varying rates (0, 1, 2, and 5% by weight) with repeated dairy manure applications over a 56-wk period was examined to evaluate the impact to leachate water quality. Increasing levels of biochar decreased cumulative levels of total N (TN) by 21 to 59%, nitrate (NO3-N) by 17 to 46%, and ammonia (NH4-N + NH3-N) by 46 to 90% in leachate but increased cumulative leaching of total P (TP). Overall leachate pH was increased and peak levels of 5-d biological oxygen demand (BOD5) in leachate after manure application were decreased with increasing levels of biochar amendment. The results from this study indicate that biochar amendments could be effective in reducing nitrogen leaching from soils, though further study is needed to determine practical application in a field setting.