Impact of nitrogen fertilizer, greenhouse, and crop species on yield-scaled nitrous oxide emission from vegetable crops: A meta-analysis

peer reviewedVegetable production is recognized as an important anthropogenic source of nitrous oxide (N2O) emission. An improved understanding of yield-scaled N2O emission from vegetable production can promote innovation for climate smart cropping. In this study, we performed a meta-analysis to quantify yield-scaled N2O emission from six types of vegetable crops, to elucidate the effects of greenhouse cultivation and different types of nitrogen (N) fertilizers on yield-scaled N2O emission from vegetable crops. Significant differences were observed in N2O emission factor (EF) and area- and yield-scaled N2O emissions among the six vegetable types. Stem and seed vegetables showed the lowest and highest area- and yield-scaled N2O emissions, respectively. The average yield of all of the vegetables was significantly higher in greenhouses than in open fields. However, only leafy vegetables were observed to have significantly lower yield-scaled N2O in greenhouses than in open fields. Emissions of yield-scaled N2O in response to inorganic N application rate differed among the different vegetable types. The replacement of inorganic N fertilizer with manure significantly reduced yield-scaled N2O emission from leafy vegetables, but significantly enhanced that from fruit vegetables. Enhanced-efficiency N fertilizer (EENF) significantly increased yield, and significantly reduced area- and yield-scaled N2O emissions from all of the vegetable types; however, it was less effective for root vegetables and open field cultivation