Assessment of biochar application to reduce nitrate leaching through agricultural vegetative treatment areas

Nitrate (NO3-) is the most prominent contaminate of private wells in Wisconsin, and agricultural has been directly linked to contributing to NO3- contamination in rural areas. There are multiple sources of NO3- from agriculture, but one that has come under scrutiny in recent years is vegetative treatment areas (VTAs) receiving silage bunker runoff. Studies have found high concentrations of NO3- in subsurface effluent of VTAs, which has result in push for management changes at agricultural facilities. One potential way to mitigate NO3- leaching through VTAs may be through biochar amendment to systems. Biochar has been proven in agronomic soils to enhance soil N retention and reduce NO3- leaching, but few studies have investigated impacts in treatment system soils. The objective of the purposed study is to evaluate the impacts of incorporating biochar into VTA soils treating silage bunker runoff to reduce nitrate (NO3-) leaching to groundwater. Specific objectives include i) comparing differences between corn stover, spoiled silage, and hardwood biochar application, ii) evaluate NO3- leaching difference between high and low temperature biochar products, iii) assess impact of biochar application rates, and iv) evaluate effects of shallow or deep tillage biochar incorporation practices on NO3- leaching. The research objectives will be evaluated using a soil column leaching approach to assess treatment impacts. Methods outlined in proposal have been used effectively to assess biochar impacts in past studies. Results from this study will be used to develop peer-reviewed publications and outreach material for other researchers and stakeholders. Outreach material will include presentations and fact sheets regarding management of VTA systems and the benefits of biochar application to mitigate NO3- leaching, to guide regulators, producers, and extension agents on how biochar can be used effectively in VTA systems to guide regulations and incentive programs.