Research trials show benefits of rolling instead of tilling – Organic Matters

Researchers at the University of Manitoba are exploring the roller crimper as a way to reduce tillage in organic agriculture.

Tillage is a key tool for organic farmers when terminating and incorporating green manures, and is also a major tool for weed control. However, it has been shown to decrease organic matter, increase the risk of erosion and dry out soil.

South American farmers developed the roller crimper to terminate green manures. U.S. Department of Agriculture researchers have worked with different forms of the tool for 12 years.

The tool crimps green manure stems and lays them flat. The green manure plant eventually dries and dies. Residue left on the soil surface creates a barrier that can suppress weeds and reduce water evaporation. The green manure still contributes nutrients to the soil and builds soil organic matter.

Farmers roll their green manure crops and seed their cash crop directly into the mulch in a single operation.

The Rodale Institute in Pennsylvania has experimented with the roller by seeding corn and soybeans directly into rolled hairy vetch or rye. Plans for building a roller are on the institute’s website and models are being tested in the United States.

I am working with University of Manitoba researcher Martin Entz to assess whether the roller crimper is suitable for green manure termination on the Prairies.

Typically, organic farmers seed green manures in the spring and terminate them at full bloom. The green manure is tilled to incorporate it into the soil, providing nutrients for subsequent crops.

But what would happen if the green manure was rolled instead of tilled? What if it remained on the surface instead of being incorporated?

U of M researchers are asking several questions about the new roller system: What effect would it have on subsequent yields? Would the nitrogen be as available? Would nitrogen be lost to the air? Will this suppress the weeds? What about soil moisture? Does it really reduce erosion?

In an attempt to answer these questions, researchers grew a pea and oat intercrop as green manure at the Carman Research Station in the summer of 2007.

The green manure was terminated at pea flowering by rolling, tilling or a combination of the two.

In the following spring, researchers seeded hard red spring wheat into the plots. Initial results show that wheat yield and grain protein were the same, regardless of whether the green manure was tilled or rolled. There was also no significant difference in soil moisture.

While weed densities were also not affected by tillage, weed species did vary with various treatments.

Researchers also compared chickling vetch, hairy vetch and Indian Head black lentil. Each green manure was rolled and tilled.

Rolling killed most of the chickling vetch and lentils and regrowth was limited. The hairy vetch continued to grow after it was rolled and produced a large amount of biomass. Wheat was seeded into the plots in the spring.

There was little ground cover from the rolled chickling vetch and lentils, but the rolled hairy vetch provided a thick mulch that appeared to suppress weeds. It also delayed the development of the wheat, and researchers are waiting to see how that will affect yields.

These initial studies indicate the potential for reducing tillage while maintaining benefits of a green manure crop. Researchers are learning that coupling the right species of green manure with the roller will be the key to maximizing its benefits.

Researchers are continuing their work this summer.

Iris Vaisman is a graduate student at the University of Manitoba. She welcomes comments at 204-474-6236 or by e-mail at

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