Separated pathways for biochar to affect soil N2O emission under different moisture contents

Dry land is a massive contributor to global nitrous oxide (N2O) production and biochar is a potential material for soil amendment that can impact soil N2O emission. Considering that the moisture content of dry land is usually changeable, it is essential to investigate the effect of biochar on soil N2O emission under different moisture contents. Therefore, column experiments were conducted with two biochars (B300 and B500, biochars pyrolyzed at 300 and 500 degrees C, respectively) under five moisture contents (18%, 21%, 24%, 27% and 30%, w/w). The results showed that B300 promoted N2O emission under the moisture contents of 18%, 21% and 24% by increasing the content of dissolved organic carbon and thus enhancing the microbial processes related to N2O production. However, when the moisture contents were 27% and 30%, the promotion of N2O productionwas overwhelmed by the improvement in N2O reduction due to the B300 induced increase in the abundance ratio of nosZ tonirS, leading to the decrease in N2O emission. Moreover, B500 did not alter the content of dissolved organic matter significantly and thus caused no significant change in N2O emissionwhen the moisture contents were 18%, 21% and 24%. But it was able to increase the abundance ratio of nosZ to nirS and thus decrease N2O emission when the moisture contentswere 27% and 30%. The results further clarified the effect of biochar on soil N2O emission and helped to evaluate the N2O-suppressing-potential of biochar. (C) 2018 Published by Elsevier B.V.