Effect of different biochar and fertilizer types on N2O and NO emissions

The use of biochar as soil improver and climate change mitigation strategy has gained much attention, although at present the effects of biochar on soil properties and greenhouse gas emissions are not completely understood. The objective of our incubation study was to investigate biochar's effect on N2O and NO emissions from an agricultural Luvisol upon fertilizer (urea, NH4Cl or KNO3) application. Seven biochar types were used, which were produced from four different feedstocks pyrolyzed at various temperatures. At the end of the experiment, after 14 days of incubation, soil nitrate concentrations were decreased upon biochar addition in all fertilizer treatments by 6-16%. Biochar application decreased both cumulative N2O (52-84%) and NO (47-67%) emissions compared to a corresponding treatment without biochar after urea and nitrate fertilizer application, and only NO emissions after ammonium application. N2O emissions were more decreased at high compared to low pyrolysis temperature. Several hypotheses for our observations exist, which were assessed against current literature and discussed thoroughly. In our study, the decreased N2O and NO emissions are expected to be mediated by multiple interacting phenomena such as stimulated NH3 volatilization, microbial N immobilization, non-electrostatic sorption of NH4+ and NO3-, and biochar pH effects. (C) 2014 Elsevier Ltd. All rights reserved.