The release of greenhouse gases from agricultural soil is important in the light of climate change. However, at the same time, the study of emissions from agriculture needs to take into account many variables, increasing the difficulty of pinpointing exactly what is causing the agricultural flux of greenhouse gases. Kurhu et al. (2011) wanted to study the impact of biochar on the release of greenhouse gases from soil in Southern Finland. They found that there were differences between the levels of carbon dioxide and nitrous oxide emissions between soils to which biochar had been added and soils to which it had not. Furthermore, although they found that biochar increased methane uptake, and also became aware of many limitations of studying biochar’s impact on the level of greenhouse gases released into the atmosphere.Nitya Chhiber
Bergstrom,I.,Karhu, K.,Matila,T.,Regina,K.,2011. Biochar addition to agricultural soil increased CH4 uptake and water holding capacity – Results from a short-term pilot field study. Agriculture, Ecosystems & Environment 140, 309–313.
Karhu et al. studied the affect of biochar on agricultural soil that was undergoing a process of five-year crop rotation. Plots were of mainly of two types: those with the addition of biochar and those without the addition of biochar. Fluxes of carbon dioxide, nitrous oxide, and methane were measured, and using linear method, related to soil water holding capacity, soil temperature, air temperature, and grain yield.
Carbon dioxide emissions were positively correlated with temperature, however, the addition of biochar increased methane uptake by a great deal but had no effect on nitrous oxide and carbon dioxide fluxes.
Methane was an interesting case as it responded greatly to rainfall; when it rained and there was higher soil water content, there was a higher methane flux from soil into the atmosphere, especially when the soil was wet and there was no biochar in the soil.
In the literature, no pattern can be found between biochar and the fluxes of carbon dioxide and nitrous oxide across experiments due to the fact that the type of biochar used in each experiment varies. Other reasons that there may be no pattern is that nitrous oxide can be produced under both aerobic and anaerobic conditions, and that higher applications of biochar may be needed in soil to actually see a difference in the fluxes of these two gases.