A Global Meta-Analysis on the Impact of Management Practices on Net Global Warming Potential and Greenhouse Gas Intensity.

Little is known about management effect on net global warming potential (GWP) and greenhouse gas intensity (GHGI) from cropland soils. Available global data from 57 experiments and 225 treatments were evaluated for individual and combined effects of tillage, cropping systems, and N fertilization rate on GWP and GHGI which accounted for CO₂ equivalents from N₂O and CH₄ emissions with or without equivalents from soil C sequestration rate, farm operations, and N fertilization. Net GWP and GHGI using soil organic C method were 66 to 71% lower with no-till than conventional till and 168 to 215% lower with perennial than annual cropping systems, but 41 to 46% greater with crop rotation than monocroppping. Both GWP and GHGI increased curvilinearly with increased N fertilization rate. Net GWP and GHGI were 70 to  87% lower in the improved combined management that included no-till, crop rotation/perennial crop, and reduced N rate than the traditional combined management that included conventional till, monocopping/annual crop, and recommended N rate. An alternative soil respiration method similarly reduced GWP and GHGI by 133 to 158% in the improved compared with the traditional combined management. Changes in GWP and GHGI due to improved vs. traditional management varied with the duration of the experiment and inclusion of soil and climatic factors in multiple linear regressions improved the relationship. Improved management reduced GWP and GHGI compared with the traditional management and the combined management was more effective than the individual management in reducing net greenhouse gas (GHG) emissions from cropland soils.