Can Use of 4R Nutrient Stewardship Practices Meet Required Emissions Reductions from Cropped Soils in the Short-Term?.

Within the next decade, greenhouse gas reductions of 30% from agriculture need to be realized if developing countries are to hope to meet international obligations. This presentation reviews results of 13 studies conducted by the University of Manitoba Soil Ecology Lab since 2004 into 4R Nutrient Stewardship practices that hold promise in achieving required nitrous oxide (N₂O) reductions from cropped soils in Manitoba, Canada. The studies broken down to component 4R practices examined are 9 studies for Right Souce, 5 for Right Rate, 3 for Right Placement and 3 for Right Timing. Of the practices examined, cropping with N fixing leguminous crops reduced emissions the most. Even plough down of leguminous green manures in late summer to provide N in organic production systems for subsequent crops resulted in little emissions of N₂O. Lowering ammoniacal N additions and increased depth of subsurface placement of N were second most effective in reducing emissions. Application of N fertilizers late in fall prior to winter soil freeze-up surprisingly had lower emissions than spring fertilizer addition. Lastly, enhanced efficiency fertilizers applied to wet soils reduced emissions. Subsurface banding of N fertilizers tended to decrease emissions but less so than the other practices previously mentioned. The potential of 4R Nutrient Stewardship practices meeting short-term nitrous oxide emissions reductions from cropped soils will be summarized.