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The objectives of this research are:

1. To assess user response to the Holos model, and the value of the model in directing actions to reduce farm greenhouse gas (GHG) emissions. 
   
   
2. To address significant knowledge gaps regarding N2O emissions from organic systems:
   • To evaluate the effect of rotations and timing of incorporation of legume forage crop residue on N availability to subsequent crops, above- and below-ground N losses, and GHG emissions.
   • To evaluate N dynamics and GHG emissions from pasture in response to urine and feces deposition.
3. To produce improved estimates of GHG emissions from eastern Canadian organic dairy farms and evaluate performance of Holos against detailed estimates.
   
   
4. To provide recommendations to guide improvements to the Holos model.

Organic dairy producers and consumers place high value on environmental sustainability, including reduction of greenhouse gas (GHG) emissions. Organic systems can reduce GHG emissions due to reduced fertilizer inputs and reduced energy use. Grazing (required under organic standards) lowers energy use and reduces emissions from manure storage. However, organic status does not guarantee lower emissions, and there will be considerable variation, depending on specific management practices. For instance, decomposition of forage residues after plowing is an important source of nitrogen for grain crops on organic dairy farms. But, some of the N will mineralize at the wrong time, leading to N losses and GHG emissions. Management of crop rotations and residues for optimal N use and reduced GHG emissions is an area that needs more study. Further, urine and feces on pasture can be significant sources of ammonia and nitrous oxide emissions, and it is important to quantify these emissions relative to confinement systems. And, unfortunately, the high-forage diets promoted within organic dairy for good cow health and farm sustainability are associated with higher methane emissions from cows, relative to higher-grain diets. On the other hand, they probably result in less nitrous oxide emissions from fields, higher soil organic matter, and lower farm energy use. There is a need to better quantify total net GHG emissions from organic dairy in Eastern Canada, and to indentify and promote best management to reduce GHG emissions from organic dairy farms. 

The new Holos model developed by Agriculture and AgriFood Canada, is a tool to estimate whole-farm, life cycle GHG emissions. Holos has strong potential for on-farm use to guide best management practices for GHG reduction, through exploring management scenarios. However, Holos has known weaknesses in distinguishing between organic and inorganic nitrogen sources, and in assessing energy use under different management. Hence, there is a need to evaluate the model for estimating GHG emissions from organic dairy farms, and to recommend any needed revisions.

This project aims to evaluate the Holos model for application on real organic dairy farms, to evaluate effects of pasturing and specific organic management practices on emissions, and to assess whole-farm GHG emissions from organic dairy systems in Eastern Canada.

The project will include a user-trial that will involve on-farm user sessions with Holos, to gauge user-response and perceived gaps in the model. It will also include two field studies. One will be conducted at Truro NS, to compare the effects of crop rotations, including comparison of spring versus fall incorporation of forage residues on N losses, GHG emissions, and N use by following grain crops. A second study near Quebec City will evaluate the impacts of urine and feces on ammonia losses and GHG emission from pasture. Finally, the research team will develop detailed estimates of GHG emissions from eastern Canadian organic dairy farms, drawing on input data collected from at least 15 farms, and information from past and current research. These estimates will be compared with Holos simulations.

The project will lead to improved estimates of emissions, recommendations for best management practices to reduce emissions, and recommendations for revisions to the Holos model for use on organic dairy farms. All aspects will support the organic dairy sector in reducing its carbon footprint.

• • Sustainability (2011) 3: 322-362
• [PDF - 4.4 MB]
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  • ASA, CSSA and SSSA International Annual Meetings. 2012
• [PDF - 33 kB]
  
  • Canadian Organic Science Conference. 2012
    

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