by Margaret Smith, PhD
Forage & Organic Agronomist

Using winter rye for weed suppression in organic no-till soybeans is moving from novelty status to a proven practice. There are still a lot of nuances to this technique, with various production aspects still being researched, tested, and refined. Even so, more and more organic producers are trying and adopting this practice.

Below are some suggested practices for success with this system.

Crop Rotation

Plant rye following a short-season crop, such as oats, peas, sweet corn or silage corn to accommodate early planting. (Results following corn harvested for grain have been poor. This rotation sequence may work with longer growing seasons in southern Iowa, central Illinois, and farther south.) Avoid growing wheat for milling after these soybeans; volunteer rye can contaminate the wheat crop.

Biomass Production Goal

Heavy rye biomass production the spring following planting is one of the keys to success with this system. The objective is to grow 8,000 to 10,000 of dry rye biomass at anthesis to fully mulch the soybeans and suppress weed growth.

Biomass production is a function of rye variety, seeding rate, seeding date, adequate fertility (particularly N), and growing conditions.

Rye Variety Selection

Researchers in Wisconsin and experienced farmers in the Upper Midwest have had success with the varieties Spooner, Aroostook, ND-Gardner and Elbon. Other varieties may work, but head and shed pollen later than these varieties.

Rye Planting Date

Early! Drill or plant rye in September in the Upper Midwest—ideally, September 1-20, up to September 30. Avoid planting in the first half of August, though. Too much fall growth can contribute to rye winterkill. Move these calendar dates sooner in central Minnesota and northern Wisconsin, and later, south of central Wisconsin and northern Iowa.

Rye Seeding Rate

Seed rye at 2,225,000 to 3,000,000 seeds/A. (Work is ongoing to further evaluate this recommendation.) The lighter seeding rate may be appropriate with earlier planting (within the guidelines provided) and good nitrogen fertility status. (Nitrogen helps encourage rye tillering.) For later planting and with lower nitrogen fertility, use the higher seeding rate.

Rolling and Crimping the Rye

In the spring, roll and crimp the rye when 100% of the plants are shedding, or have shed, pollen (anthesis). Because rye varieties are composed of diverse genetic populations, when the last plants reach anthesis, some earlier plants will be more mature. Rolling before full anthesis will result in some plants “righting” themselves.

Some rye plants in this system can produce viable seed, which may volunteer later. These seed producing plants can be on either the early or late end of flowering. After waiting for the last plants to shed their pollen before crimping, the earliest flowering plants within the population may produce viable seed. On the other hand, if rolled and crimped too soon, those plants that right themselves may continue maturing and produce viable seed.

Soybean Planting

Plant soybeans at the same time—either just before or just after rolling the rye. Some farmers have had better success getting seed into the ground by planting soybeans into the standing rye first and immediately rolling after planting. If rolling and planting are separate operations, match equipment width and drive the same direction for both operations.

Other farmers have experimented with planting green about two weeks before rolling, with the objective to roll rye at anthesis when soybeans are between V1 and V3 growth stages. Disturbing rye earlier with the planter can delay maturity and spread the time period to achieve 100% anthesis. This planting window/timing has not yet been perfected.

Soybean Row Spacing and Planting Rate

Plant soybeans in 30-inch rows at 225,000 seeds/A. Excellent seed placement and covering may allow for lighter planting rates. When using this systems, monitor at-harvest soybean plant populations before lower these rates.

Some farmers use 15-inch rows spacing or drill their soybeans, but then give up the option, if needed, to run a cultivator with single sweep later in the season.

Planter Modifications

For planting soybeans AFTER rolling and crimping the rye cover crop, add weight or down-pressure to the planter.

Resources for rolled and crimped rye in organic soybean production:

We now have a lot of resources, as well as farmer experiences, to support these recommendations—with more available each year.

Wisconsin—University of Wisconsin Organic Program

Work of Dr. Erin Silva at the University of Wisconsin, Madison

Published research on the topic

New York—Cornell University

Iowa—Practical Farmers of Iowa

Illinois—Western Illinois University

Work of Dr. Joel Gruver at WIU at Macomb, IL

Indiana—Purdue University

Good summary from Michael O’Donnell at Purdue. He provides info for both organic and conventional operations.

USDA—Beltsville Maryland

Work of Dr. Steven Mirsky’s with the USDA Agricultural Research Service (ARS) at Beltsville, MD

Minnesota—Albert Lea Seed

Pennsylvania—Rodale Institute

Ontario, Canada—Ontario Ministry of Agriculture, Food, and Rural Affairs

South Dakota—South Dakota State University

  • Soybean Rolling: Yield Effects  Summary report of Iowa and Minnesota data generated in conventional soybean systems, with application for organic soybeans