Biochar effect on the mineralization of soil organic matter

The objective of this work was to verify whether the addition of biochar to the soil affects the degradation of litter and of soil organic matter (SUM). In order to investigate the effect of biochar on the mineralization of barley straw, soil was incubated with C-14-labelled barley straw with or without unlabelled biochar. To investigate the effect of straw on the mineralization of biochar, soil was incubated with C-14-labelled biochar with or without straw. In addition, to investigate the effect of biochar on old SUM, a soil labelled by applying labelled straw 40 years ago was incubated with different levels of biochar. All experiments had a control treatment, without any soil amendment. The effect of biochar on the straw mineralization was small and nonsignificant. Without biochar, 48+/-0.2% of the straw carbon was mineralized within the 451 days of the experiment. In comparison, 45+/-1.6% of C was mineralized after biochar addition of 1.5 g kg(-1). In the SUM-labelled soil, the organic matter mineralized more slowly with the increasing doses of biochar. Biochar addition at 7.7 g kg(-1) reduced SUM mineralization from 6.6 to 6.3%, during the experimental period. The addition of 15.5 g kg(-1) of biochar reduced the mineralized SUM to 5.7%. There is no evidence of increased degradation of either litter or SUM due to biochar addition; consequently, there is no evidence of decreased stability of SOM.