Annual nitric and nitrous oxide emissions response to biochar amendment from an intensive greenhouse vegetable system in southeast China

Biochar impact on soil nitrous oxide (N2O) and nitric oxide (NO) emissions from intensive greenhouse vegetable cropping systems is not well established. Annual soil N2O and NO emissions were simultaneously measured from a typical greenhouse vegetable field treated with different biochar application rates in southeast China. Both N2O and NO emissions differed greatly across the individual vegetable cropping seasons, of which being higher in green soybean and tomato growing seasons, respectively. Over the annual vegetable cropping rotation, biochar amendment decreased soil N2O and NO emissions by 10–23% and 18–19% relative to N fertilization alone, respectively. Biochar rate of 20 t ha−1 gained the lowest N2O and NO emissions over the annual cycle. The ratio of NO/N2O was negatively correlated with soil moisture and depends on biochar addition or not. On average, annual emission factor (EF) of N2O and NO combined was accounted for 2.13% with biochar amendment, which was decreased by 22% compared with N fertilization alone (EF = 2.74%). Vegetable yield was significantly enhanced under the biochar combined with N fertilizer plots relative to control, while there is no difference among the N fertilization treatments with or without biochar amendment. Therefore, biochar could be used as an effective management mitigating soil N2O and NO emissions while maintaining crop yield in greenhouse vegetable cropping systems in southeast China.