Fluxes of Reactive Nitrogen and Greenhouse Gases from Arable Land in South-Western Ukraine

Conventional wisdom has it that farmland emits lots of reactive nitrogen and greenhouse gases, especially farmland getting big inputs of nitrogen fertilizer. But realistic reduction strategies cannot be developed without measurements spanning at least a whole year to determine region-specific, soil-specific, crop-specific annual fluxes. For the first time, in situ measurements of soil-atmosphere fluxes of Nr and GHGs from Southern Black Soils in Ukraine prove them to be no more than a modest source of N2O; the fertilizer-induced emission factor (EFN2O, estimating the percentage of fertilizer N that is lost as gaseous emissions) is far below the levels suggested by IPCC. Moreover, under winter crops with low N-fertilizer application, they are a sink for CH4 and NH3. Measurements also reveal the influence of the weather and soil management practice: for instance, fertigation of vegetable crops and dry–wet cycles triggered pulses of NO and EFNO.