Effects of Slow Pyrolysis Biochar on CO2 Emissions from Two Soils under Anaerobic Conditions

Abstract

The amendment of sandy Haplic Arenosol and clayey loam Gleyic Fluvisol with two rates of biochar derived from the slow pyrolysis of wood feedstock was evaluated under anaerobic conditions in a 63-day laboratory experiment. The rates of biochar were 15 and 30 t ha−1. Both rates of biochar were applied either with or without 90 kg ha−1 of nitrogen fertilizer (NH4NO3). Soils with no amendments were used as control treatments. Our results showed that only the incorporation of 15 t ha−1 of biochar, compared with the control treatment, led to a significant (p < 0.05) increase in volumetric water content of the sandy soil and a significant (p < 0.05) decrease in the parameters of the clayey loam soil. Increasing the biochar rate from 15 to 30 t ha−1 did not result in significant changes in volumetric water content in either type of soil. In the sandy soil, CO2 emissions were significantly (p < 0.05) higher in the treatments of 15 and 30 t ha−1 with N fertilizer compared with the control and N fertilizer treatment. In the clayey loam soil, the combined application of both rates of biochar with N fertilizer caused no significant increase in CO2 emissions compared with the control and N fertilizer treatment. The incorporation of 30 t ha−1 of biochar into the sandy soil contributed to a significant (p < 0.01) increase in the cumulative CO2 flux compared with the control treatment. Application of 15 and 30 t ha−1 of biochar into the clayey loam soil led, respectively, to a significant (p < 0.05) and a nonsignificant increase in the cumulative CO2 fluxes compared with the control treatment.