Find in Library

Biochar, a carbon-rich, porous pyrolysis product of organic residues may positively affect plant yield and can, owing to its inherent stability, promote soil carbon sequestration when amended to agricultural soils. Another possible effect of biochar is the reduction in emissions of nitrous oxide (N₂O). A number of laboratory incubations have shown significantly reduced N₂O emissions from soil when mixed with biochar. Emission measurements under field conditions however are more scarce and show weaker or no reductions, or even increases in N₂O emissions. One of the hypothesised mechanisms for reduced N₂O emissions from soil is owing to the increase in soil pH following the application of alkaline biochar. To test the effect of biochar on N₂O emissions in a temperate maize cropping system, we set up a field trial with a 20t ha^&minus;1 biochar treatment, a limestone treatment adjusted to the same pH as the biochar treatment (pH 6.5), and a control treatment without any addition (pH 6.1). An automated static chamber system measured N₂O emissions for each replicate plot (<i>n</i> = 3) every 3.6 h over the course of 8 months. The field was conventionally fertilised at a rate of 160 kg N ha^&minus;1 in three applications of 40, 80 and 40 kg N ha^&minus;1 as ammonium nitrate. <br><br> Cumulative N₂O emissions were 52 % smaller in the biochar compared to the control treatment. However, the effect of the treatments overall was not statistically significant (<i>p</i> = 0.27) because of the large variability in the data set. Limed soils emitted similar mean cumulative amounts of N₂O as the control. There is no evidence that reduced N₂O emissions with biochar relative to the control is solely caused by a higher soil pH.