Combined effects of nitrogen fertilization and biochar on the net global warming potential, greenhouse gas intensity and net ecosystem economic budget in intensive vegetable agriculture in southeastern China

Field experiments were conducted to determine the effects of nitrogen (N) fertilization and biochar addition on the net global warming potential (net GWP), greenhouse gas intensity (GHGI) and net ecosystem economic budget (NEEB). These experiments were conducted in an intensive vegetable field with 4 consecutive vegetable crops in 2012 and 2013 in southeastern China. The experiment was conducted with a 32 factorial design in triplicate at N fertilizer rates of 0, 1475, 1967 kg N ha−1 and biochar rates of 0, 20, and 40 t ha−1. Although CH4 emissions were not obviously affected by N fertilization, N2O emissions increased by 27.2–116.2% and the net GWP increased by 30.6–307.2%. Consequently, the GHGI increased significantly, but vegetable yield and the NEEB did not improve. Furthermore, biochar amendments did not significantly influence CH4 emissions, but significantly decreased the N2O emissions by 1.7–25.4%, the net GWP by 89.6–700.5%, and the GHGI by 89.5–644.8%. In addition, vegetable yields significantly increased by 2.1–74.1%, which improved the NEEB. Thus, N fertilization did not increase vegetable yields or the NEEB. However, N fertilization did increase the net GWP and GHGI. In contrast, biochar additions resulted in lower N2O emissions and net GWP and GHGI, but increased vegetable yield and the NEEB in the intensive vegetable production system. Therefore, appropriate biochar amendment should be studied to combat changing climate and to improve the economic profits of vegetable production.