Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/6/2014
Publication Date: 9/26/2014
Citation: Lentz, R.D., Ippolito, J.A., Spokas, K.A. 2014. Biochar and manure effects on net nitrogen mineralization and greenhouse gas emissions from calcareous soil under corn. Soil Science Society of America Journal. 78:1641-1655.
Interpretive Summary: Amending soils with biochar, a byproduct of bio-oil production and the incomplete combustion of biomass, potentially could remove excess atmospheric CO2 and help reverse climate change while improving soil quality. Yet few multi-year field studies have examined the impact of biochar application on important soil biological processes such as the production of plant-available nitrogen from soil organic matter (net N mineralization) and greenhouse gas emissions, particularly in irrigated, calcareous soils. This research found that a one-time biochar addition produced persistent soil effects. While the biochar-only treatment demonstrated a potential to increase corn yields and minimize CO2-C and N2O-N gas emissions in these calcareous soils; biochar also caused decreased corn yields under certain soil nutrient conditions. However, combining biochar with manure effectively utilizes these soil amendments. The combination eliminated potential yield reductions and maximized manure net N mineralization potential. This information helps farmers understand how biochar soil amendments can best be used to increase soil productivity.
Technical Abstract: Few multiyear field studies have examined the impacts of a one-time biochar application on net N mineralization and greenhouse gas emissions in an irrigated, calcareous soil; yet such applications are hypothesized as a means of sequestering atmospheric CO2 and improving soil quality. We fall-applied four treatments, stockpiled dairy manure (42 Mg/ha dry wt.); hardwood-derived biochar (22.4 Mg/ha); combined biochar and manure; and no amendments (control). Nitrogen fertilizer was applied in all plots and years based on treatment’s pre-season soil test N and crop requirements, and accounting for estimated N mineralized from added manure. From 2009 to 2011 we measured greenhouse gas fluxes using vented chambers, net N mineralization (NNM) using buried bags, corn yield, and N uptake, and in a succeeding year, root and shoot biomass and biomass C and N concentrations. Both amendments produced soil produced persistent soil effects. Manure increased seasonal and three year cumulative NNM, root biomass, and root:shoot ratio 1.6-fold, CO2-C gas flux 1.2-fold, and reduced soil NH4:NO3 ratio 58% relative to no-manure treatments. Relative to all other treatments on average, biochar-only produced 33% less cumulative NNM, 20% less CO2-C and 50% less N2O-N gas emissions, 35% less root biomass, and increased soil NH4:NO3 ratio 1.8-fold. These long-term effects suggest that biochar slightly impaired nitrification and N immobilization processes, and are likely caused by enduring biochar porosity and surface chemistry characteristics that influence N-transform-ation processes, alter microbial populations, and sequester soil ammonium. While the biochar-only treatment demonstrated a potential to increase corn yields and minimize CO2-C and N2O-N gas emissions in these calcareous soils; biochar also caused decreased corn yields under certain soil nutrient conditions. Combining biochar with manure effectively utilizes these soil amendments as it eliminated potential yield reductions and maximized manure net N mineralization potential.