Effect of Biochar on Soil Greenhouse Gas Emissions at the Laboratory and Field Scales
2019
Fidel, Rivka B. | Laird, David A. | Parkin, Timothy B.
Biochar application to soil has been proposed as a means for reducing soil greenhouse gas emissions and mitigating climate change. The effects, however, of interactions between biochar, moisture and temperature on soil CO<inf>2</inf> and N<inf>2</inf>O emissions, remain poorly understood. Furthermore, the applicability of lab-scale observations to field conditions in diverse agroecosystems remains uncertain. Here we investigate the impact of a mixed wood gasification biochar on CO<inf>2</inf> and N<inf>2</inf>O emissions from loess-derived soils using: (1) controlled laboratory incubations at three moisture (27, 31 and 35%) and three temperature (10, 20 and 30 °C) levels and (2) a field study with four cropping systems (continuous corn, switchgrass, low diversity grass mix and high diversity grass-forb mix). Biochar reduced N<inf>2</inf>O emissions under specific temperatures and moistures in the laboratory and in the continuous corn cropping system in the field. However, the effect of biochar on N<inf>2</inf>O emissions was only significant in the field and no effect on cumulative CO<inf>2</inf> emissions was observed. Cropping system also had a significant effect in the field study, with soils in grass and grass-forb cropping systems emitting more CO<inf>2</inf> and less N<inf>2</inf>O than corn cropping systems. Observed biochar effects were consistent with previous studies showing that biochar amendments can reduce soil N<inf>2</inf>O emissions under specific but not all, conditions. The disparity in N<inf>2</inf>O emission responses at the lab and field scales suggests that laboratory incubation experiments may not reliably predict the impact of biochar at the field scale.
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