Organic Broadcaster

Research on organic no-till makes strides with focus now on increasing yields

By Kathleen Delate

Seven weeks after roller crimping with the Dawn ZRX roller, the rye mulch is suppressing most weeds in the soybeans at Iowa State University’s research farm. Photo by Kathleen Delate

Reduced tillage or no-till can provide multiple environmental benefits, particularly in the area of soil conservation, as well as reducing costs for machinery, labor, and fuel. Organic no-till has unique challenges in that herbicides cannot be used to terminate cover crops as in conventional no-till. Researchers have been looking into best practices for organic no-till since 2005. We have learned an incredible amount from these organic no-till studies, but the challenge remains to balance improving soil quality with maintaining optimal yields. That is the focus of our current research. 

At Iowa State University, we are working with Erin Silva and Brian Luck at the University of Wisconsin-Madison, along with farmer-cooperators in Iowa, Wisconsin, and Pennsylvania (Rodale Institute) on a USDA-NRCS Conservation Innovation Grant examining different equipment and settings to increase yields in organic no-till systems. The methods include planting a cover crop (rye for soybeans; hairy vetch for corn; and a mixture for vegetables) in the fall, and, in the spring when grass cover crops have reached anthesis (pollen shed), using a tractor to push or pull the roller crimper to crush cover crops in place of herbicide termination to fit within organic rules. The roller crimper is filled with water to weigh 2,000 pounds.

Several companies now manufacture roller crimpers. In addition, one can be fabricated using plans published on the Rodale website (

We have researched two types of rollers: Rodale’s and the ZRX zone roller from Dawn Manufacturing (Sycamore, Illinois). The roller crimper Rodale has promoted works well on flat ground, pushed in front of the tractor, with a no-till planter pulled behind the tractor in a one-pass operation. Dawn uses individual rollers set up on planter rows, so 6 rollers are needed for a six-row planter. It has more down pressure due to hydraulics, unlike the Rodale roller, whose extra weight comes from filling it with water. It is also more flexible for rolling rye on hillier ground, due to their articulated design. 

Planter design/set-up is also critical. Having extra down pressure on the planter helps get good seed-to-soil contact through the rolled mulch. Having a good planter also includes good pressing wheels and steel, furrow-closing wheels with adjustable down pressure to get the soil firmed after planting and pull the rye mulch over the row. Because of the restriction on herbicides, all your weed management will be based on the mulch cover within and between crop rows, so any gaps can quickly fill with weeds. Planting at a high rate—at least 170,000 seeds per acre—will also help with weed management.

If weeds become too extensive, be prepared to cultivate with a high-residue cultivator (e.g., Hiniker, Mankato, Minnesota). As one farmer told me, it’s better to “only cultivate once and get that carbon-rich rye crop in your ground, than doing four normal organic tilled weed management tillage operations.” 

Yield is the elusive element and requires these three factors: good seed emergence, good mulch-supported weed management, and enough rain to fill pods—and no hail, which hit some fields in Iowa during the derecho of August 10. Over the years, organic no-till soybeans have ranged from 20 bu/acre in drier years to 50 bu/acre when rains hit just right. 

Weather still seems to be the most critical factor for success. If you plant and there’s no rain, the thick mulch can hurt and slow emergence. Early wet weather can be damaging, too; it leads to slow cover crop decomposition, which invites moisture-loving insects like seed corn maggot and armyworms—several growers had issues with those pests this year. In typical organic tilled conditions, the ground is exposed, dries out somewhat, and is less prone to insect problems. Consistent, non-excessive rains lead to the best results, allowing the soybeans to canopy quickly and preventing weeds from emerging in any gaps in the cover crop mulch.

After 15 years of research on organic no-till in the Midwest, we are still looking at organic soybeans into rolled rye, which shows the most promise, although it still not a perfect system. Cindy Cambardella, soil scientist at USDA-Agricultural Research Service in Ames, Iowa, has consistently found higher soil quality in organic no-till systems, as the cover crop adds significant carbon and microbial biomass. Soil in plots with cover crops and no-till supported the greatest levels of carbon, microbial populations, and nutrients.

While conventional no-tillers cite many of these same soil conservation benefits, organic no-till should never be compared to conventional no-till, which has consistent results in cover crop termination because of the use of a herbicide (glyphosate). Glyphosate is listed as a probable carcinogen by the International Agency for Research on Cancer of the World Health Association. In addition, glyphosate use is associated with herbicide-resistance across the countryside. 

Summer 2020 Studies

At the Levi Lyle Farm in Keota, Iowa, soybeans were planted into mature rye on June 2, comparing the Rodale and Dawn rollers; 15- vs. 30-inch rows; and an electric WeedZapper™ (Old School Manufacturing, Sedalia, Missouri). Soybeans have been productive in both systems, spared by the derecho, with harvest in October. There appears to be a trend towards greater weed management in the Rodale-roller side of the demonstration plots. The WeedZapper™ killed most weeds above the soybean canopy; we are anxious to see if this will translate into a yield bump. 

Iowa State University partnered with Practical Farmers of Iowa on two field days this summer on Lyle’s farm: the first, on June 2, demonstrated the process of roller crimping and planting; the second, a month later, showed how the WeedZapper™ worked. Click to watch the field day videos. 

At Iowa State University’s Neely-Kinyon Farm in Greenfield, we are seeing, once again, that rain is proving to be a critical factor for high yields in organic no-till vegetables. Also, organic no-till favors broad-leafed vegetables that form a rapid canopy, like squash, to compete with weeds that may emerge through the decaying mulch. A thick mulch from a high seeding rate will assist with weed management throughout the season. Hand-weeding and irrigation can help the organic no-till system in vegetables, unlike field soybeans and corn that must rely on sufficient rain. As of early September, over 15% of Iowa is considered to be in severe drought, with most farmers across the state needing rain. 

In our virtual field day Sept. 9 at the Neely-Kinyon Farm, we show how the roller crimper worked on our vegetable plots. The vegetable plots are shown about 15 minutes into the video.

One last point in favor of organic no-till: We’ve found that nitrate leaching is reduced in the cover-crop-based systems compared to completely tilled plots; so organic no-till offers extra benefits for farmers concerned about potential nitrogen pollution from manure applications. 

We hope to update everyone about our research trials at conferences being held virtually this winter, including the Iowa Organic Conference November 23 and the MOSES Conference in February. 

Kathleen Delate is a professor in the Organic Agriculture Program at Iowa State University.

From the September | October 2020 Issue


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