Biochar Reduced Nitrous Oxide and Carbon Dioxide Emissions from Soil with Different Water and Temperature Cycles

Interactions among biochar, respiration, nitrification, and soils can result in biochar increasing, decreasing, or not impacting greenhouse gas (GHG) emissions. This experiment determined the impact of water‐filled porosity (WFP) and corn ( Zea mays L.) stover biochar on CO 2 and N 2 O emissions in May (spring) and August (summer). The May experiment contained two N rates [0 and 224 kg Ca(NO 3 ) 2 –N ha −1 ], whereas the August had three N rates [0, 224 kg Ca(NO 3 ) 2 –N ha −1 , and 224 kg (NH 4 ) 2 SO 4 –N ha −1 ]. The average temperatures in the May and Augusts 2014 experiments were 14 and 24°C, respectively. Biochar reduced CO 2 –C emissions in the high WFP Ca(NO 3 ) 2 treatment in the May and August experiments 15.4 and 16.3 kg ha −1 , respectively. Associated with the CO 2 –C decrease was a 15.7% reduction in the soil solution dissolved organic C. In addition, N 2 O–N and CO 2 –C emissions were not correlated in the May Ca(NO 3 ) 2 ha −1 treatment, whereas in the August experiment, N 2 O–N and CO 2 –C emissions were correlated ( r 2 = 0.98, P < 0.01). In August, biochar increased the apparent nitrification from 16 to 25 kg NH 4 –N (ha × d) −1 in the low WFP (NH 4 ) 2 SO 4 treatment, and it did not influence the nitrification rate in the high WFP (NH 4 ) 2 SO 4 treatment. In general, N 2 O–N emissions increased with WFP and N rate and were reduced 21.7% by biochar. The findings suggest that multiple mechanisms contributed to N 2 O emissions and seasonal differences in soil temperature could result in biochar having a mixed impact on GHG emissions. Core Ideas Biochar reduces CO 2 gas emission from soil in high soil temperature. Biochar reduces N 2 O gas emission from soil in high soil temperature. Biochar reduces N 2 O gas emission from high water‐filled porosity condition.