OSCII Activity A.8

Optimizing green manure and fertility management for organic cereal production

Activity summary

Canadian organic farmers have identified promoting biologically-based soil fertility management strategies under legume-based crop production systems as a high research priority. In a recent (OACC, 2009) survey of Canadian organic farmers, their top six research priorities were research focused on (i) soil fertility and crop rotations, (ii) consumer education on organic system benefits, (iii) beneficial rotations for specific problems, and (iv,v,vi) rotation impact on soil quality, ecological interactions and soil life. Crop yields under organic management, particularly for cash crops, continue to lag conventional production, with nitrogen and phosphorus appearing to be a critical weak link in soil fertility management for major commodities, negatively impacting on both yield and quality (Turmel et al, 2009). The general objectives of the proposed research are to develop improved agronomic strategies for green manure management and soil and fertility management for organic grain production in Eastern and Western Canada. Elaborating an improved and more systematic approach to soil and fertility management for organic crop production, by improving cost-efficiency and sustainability of Canadian organic production, will have immediate and long-term economic benefits for the sector. The project will also improve the understanding of the benefits of improved agronomic practices within organic grain systems on soil quality and soil health.

Inadequate fertility management has multiple and interrelated negative impacts on the sustainability of organic field crop production, including (i) reduced green manure biomass and seed production, (ii) reduced grain cash crop yields and quality of grain (low test weight, protein and phosphorus content), (iii) reduced return of crop residue to promote labile and stable pools of soil organic matter, and (iv) has even been suggested to reduce the carbon use efficiency of soil microbial decomposer populations. Novel green manure types and management strategies (seeding date, no-till termination) integrated with tactics such as banding of biofertilizer supplement, etc., have been tested on selected grain cropping research trials primarily in the US in recent years. In Canada, various biofertilizers have become increasingly available that may provide a targeted source of supplemental nitrogen (N) and phosphorus (P) for organic grain systems. Finally, agronomic strategies for cereal production involving selected and more novel green manures may have broader environmental and ecological benefits with respect to soil carbon storage and soil quality, nutrient use efficiency and N losses, and even enhancement of native pollinators and pollination efficacy. These agronomic responses and environmental/ecological benefits are expected to vary significantly with climate and agroecosystem broadly, and also farm/site management and landscape specific factors. Thus, for a comprehensive elaboration of an improved agronomic strategy for fertility management for Canadian organic grain producers, it is critical that a systematic, integrated approach involving a networked, multi-region research program as proposed here is undertaken.

Using a combination of replicated research trial sites (at Dalhousie University (Atlantic Canada); Université Laval (Québec); Alfred Campus/University of Guelph (Ontario) and University of Manitoba (Manitoba)) and participating producer field sites in each of these regions, the research will examine grain crop (wheat, corn) nutrient uptake, yield and quality, plus soil quality and N and P dynamics as affected by type of selected novel green manure precrops (with a primary focus on hairy vetch compared with red clover or alfalfa), green manure agronomic management (variety, crop mixture, incorporation dates, and termination strategy), with or without biofertilizer supplementation. Green manure biomass and productivity as affected by planting date, and overwinter persistence will be determined. In addition, impacts of these strategies on synchrony of soil N and P release to plant uptake, grain yield and quality, post-harvest soil mineral N levels, and changes to soil quality will be evaluated at all research sites. An economic evaluation of the treatments will also be a key approach. On selected sites, novel strategies such as no-till termination of green manures, and banding of biofertilizers will be included as treatments. The response of wheat variety to green manure and fertility management, plus green manure underseeding regime will be an additional focus of the trials at the Alfred Campus of the University of Guelph, while the investigation of green manure productivity as affected by both soil fertility and whole farm nutrient use and efficiency will be conducted on Prairie grain farms in Manitoba.

The project brings together industry sponsors and partners from across the spectrum of organic crop production, including organic biofertilizer producers and suppliers (Acti-Sol Inc., Québec; Buckingham Organics and Homestead Organics Ltd., Ontario), organic grain end users (Organic Valley; Homestead Organics Ltd.) and producer groups (including Farmer Direct, Regina representing over 60 Prairie organic farms; Coop Agrobio (18 Quebec organic grain farms)) and individual producers in each region. 

Activity researchers

Name Affiliation
Derek Lynch, Activity Leader Dalhousie University
Valérie Bélanger Université Laval
Martin Entz University of Manitoba
Simon Lachance University of Guelph, Alfred Campus
Ashraf Tubeileh University of Guelph
Anne Vanasse Université Laval
Paul Voroney University of Guelph
Emmanuel Yiridoe Dalhousie University