N2O SOIL EMISSIONS AFTER BIOCHAR AMENDMENT: CONTRASTING RESPONSES DEPENDING ON THE ORIGINAL FEEDSTOCK

Abstract

It has been demonstrated that biochar addition to soils reduces N2O emissions in most cases (Cayuela et al., 2014). In this sense, molar O/C and H/C ratios are considered useful indicators to evaluate biochar recalcitrance and its potential in reducing GHG emissions (Spokas, 2010; Cayuela et al., 2015). Nevertheless, biochar properties depend on their feedstocks as well as on the pyrolysis conditions such as heating rate, highest pyrolysis temperature or residence time (Downie, 2011). Thus, generalizations about biochar GHG mitigation potential remain elusive due to the high heterogeneity of biochar properties and reactivity in soils. In an effort to elucidate how biochars made from different feedstocks would affect N2O release from agricultural soils, laboratory soil incubations in optimum conditions for denitrification were conducted. Eleven residues from the agricultural and agro-industrial sector widely available in the Mediterranean area were selected as feedstocks.