Cover crop-driven organic no-till soybean production in Ontario

Typically, it’s tough to grow organic soybeans without turning to tillage for weed control. When done well, organic yields can rival conventional production, but it comes at a cost — from equipment and labour requirements to long-term soil degradation.

There are production systems, however, that are proving to deliver yield without these drawbacks. In the U.S, growing evidence supports the potential for cover crop-based organic no-till soybeans, says Jake Munroe, soil management specialist for the Ontario Ministry of Agriculture, Food and Rural Affairs..

Munroe is now teaming up with the Ontario Soil and Crop Improvement Association to carry out a two-year study to evaluate the potential of organic no-till soybean production in Ontario. In this interview with RealAgriculture’s Bernard Tobin, Munroe shares 2019 findings, the first year of the study.

Munroe explains that a roller crimper, a drum with chevron-shaped blades, can be used to crimp the stems of the cover crop such as rye once it’s flowering. This effectively kills the cover crop. Soybeans are then seeded into the mulch, which, if thick enough, can provide season-long weed suppression. The cover crop-based organic no-till system also offers advantages in terms of labour savings and soil health improvements, he notes. (Story continues after the interview.)

A thick stand of rye is critical for success, says Munroe. It prevents weed germination and growth, particularly of small-seeded annuals. Vigorous spring growth is also important, allowing the rye to compete with weeds.

Overall, Munroe was pleased with the results of first-year trials given the difficult early-season planting and growing conditions. The organic no-till soybeans yielded 8.6 bu/ac less than the tillage-based soybeans at the Drayton, Ont., test site. Given that the no-till soybeans spent a full month – from seeding to crimping – under the canopy of the rye cover crop, this was a surprisingly small yield difference, he says. The no-till soybean plants, despite their small size, had a comparable number of pods but had smaller beans and fewer beans per pod.

At the Elora, Ont., test location, roller crimped soybeans yielded 14.3 bushels/acre less than those in the no-rye control treatment. A poor soybean stand in the roller crimped treatment was likely the main contributor to the lower yield, says Munroe. A sub-90,000 soybean stand, planted on June 12th, was not able keep up with the full stand in the no-rye control treatment. The mulch generally provided sufficient weed suppression through the critical weed-free period (V1-V3), though warm-season grasses emerged later in the season and produced viable seed by harvest.

Munroe notes four key takeaways from year one of the research:

  • Select fields with low perennial weed pressure and decent background fertility.
  • Seed rye early and thick to achieve sufficient biomass
  • Use well-maintained planting equipment to ensure good cutting of the rye mulch and placement of soybeans.
  • Seed soybeans at a high rate (minimum of 250,000 up to 300,000+ seeds/acre).

Check our Munroe’s full report on Field Crop News.

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