Net global warming potential and greenhouse gas intensity

Abstract Agricultural practices contribute significant levels of greenhouse gas (GHG) emissions. Methods to measure net global warming potential (GWP) and greenhouse gas intensity (GHGI) that account for all sources and sinks of GHG emissions in agroecosystems are still evolving. Sources of GHGs include soil CO 2 , N 2 O, and CH 4 emissions and CO 2 emissions associated with farm operations, N fertilization, and other chemical inputs. Sinks of GHGs include CH 4 uptake, soil C sequestration, and crop residue returned to the soil. This chapter discusses the methods of measuring net GWP and GHGI using two approaches: In the soil organic C (SOC) method, net GWP and GHGI are calculated by using N 2 O and CH 4 emissions (or CH 4 uptake), as well as CO 2 emissions from farm operations, N fertilization, and other chemical inputs as GHG sources and C sequestration rate (ΔSOC) as GHG sink. In the soil respiration method, soil respiration (excluding root respiration) is included as another GHG source, and the previous year's crop residue returned to the soil instead of ΔSOC is included as GHG sink in addition to the above parameters. Advantages and drawbacks of each method of calculating net GWP and GHGI are also discussed.