Organic Farming Methods Enhance Soil Organic Matter

Organic Agriculture Centre of Canada

Member countries of the European Union, operating under the Common Agricultural Policy, make direct "green payments" to organic farmers or to farmers who are in the process of transitioning to an organic system. The general philosophy behind these payments is that organic farmers are offering an environmental service to their countries. In Canada, on the other hand, where the body of research in support of organic agriculture is not as extensive as that in Europe, policy makers regard the organic trend as less of a solution to current environmental concerns and more of a method by which farmers can access a lucrative market driven by health conscious consumers. As a result, there are virtually no federally financed initiatives for farmers considering the economically challenging, three year transition to organic certification, the consequences of which will be felt by both Canadian farmers and non-farmers alike.

In response, and with the aim of influencing Canada’s policy makers, Dr. Derek Lynch of the Nova Scotia Agricultural College has published a paper, "The Environmental Impacts of Organic Agriculture", which compiles North American based organic research in one persuasive document. Particularly timely, given the industrial community’s scramble to offset carbon dioxide emissions by carbon sequestration, is the section of Lynch’s paper that discusses the role of soil organic matter and soil health in the storage of organic carbon. He suggests that organically managed agricultural soils, with their high levels of SOM and substrate diversity, are better able to capture and retain carbon than the soils of conventionally managed systems. Also compelling, especially as farmers grapple with the adverse environmental conditions associated with global warming, is the implication that the higher soil organic matter levels associated with organic management contribute to crop yield stability and production resilience.

One measurement of a soil’s health is in the wealth and diversity of its biological community. Lynch refers to two studies from Atlantic Canada and the University of Manitoba, both of which demonstrate that organically managed soils exhibit larger earthworm, microbial and mycorrhizal populations than conventionally managed soils. Lynch also notes that a soil’s ability to capture and retain carbon is a direct result of this increased health and diversity. Historically, however, organic farming, with its reliance on mechanical tillage for weed control and for the incorporation of green manures, has been criticized for its contribution to soil carbon loss. Lynch, however, presents several convincing studies whose conclusions would suggest otherwise.

He cites a 9-year study at USDA-ARS Beltsville, MD comparing the effect of management systems on soil total carbon and nitrogen concentrations. Interestingly enough, the study concluded that, as a result of increased soil productivity, soil carbon and nitrogen concentrations were 19 and 23% greater, respectively, in the organic system that utilized cover crops, animal manures and mechanical cultivation for weed control than in the conventional no-till and reduced input no-till systems. These results are closely mirrored by a similar, 7 year study out of Michigan comparing the effect of grain management systems on soil carbon and nitrogen concentrations. This study also concluded that soil carbon and nitrogen pools were enhanced by the organic management system.

Lynch also suggests that increased soil health and soilorganic matter associated with organic management systems contributes to both crop yield stability and production resiliency. For example, the Maine Potato Ecosystem Study, reporting on 13 years of research, concluded that potatoes grown in 2 year rotations in a system amended with compost and green manures were markedly less influenced by adverse conditions, like drought, than potatoes grown in a conventional system. Similarly, a 10 year comparative farming system trial at the Rodale Institute Farming Systems Trial in Kutztown, PA determined that during 5 dry years, corn yields were highest in the organically managed soils that, incidentally, had the highest soil organic matter levels.

Dr. Lynch’s review persuasively contends that the enhanced levels of soil organic matter and biological diversity in organically managed soils result in environmentally resilient agricultural systems with an ability to capture and retain substantial amounts of carbon. As Canada’s policy makers face the tough challenges of cutting carbon dioxide emissions, Lynch’s impressive body of evidence in support of organic agriculture should be viewed as a realistic solution to an undeniable problem. Central to that solution are Canada’s organic farmers, whose indisputable contribution to this country’s food security and environmental health should be generously supported, for the sake of all Canadians.

This article was written by Tanya Brouwers on behalf of the OACC with funding provided by Canada’s Organic Science Cluster (a part of the Canadian Agri-Science Clusters Initiative of Agriculture and Agri-Food Canada's Growing Forward Policy Framework).  The Organic Science Cluster is a collaborative effort led jointly by the OACC, the Organic Federation of Canada and industry partners
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This article is Part 3 of a series based on Derek Lynch's 2009 paper, "The Environmental Impacts of Organic Agriculture: A Canadian Perspective". Click here to see Part 1, Part 2 and Part 4.

Posted March 2010