Cereal Rye: Late Summer / Fall Seeding Rates For Corn And Soybean Systems
Author: ISAP Soil Health Specialist, Jim Isermann
For many farmers, harvest season also can entail seeding time for cover crops. There are many options of cover crops, but as the fall moves on and the calendar page turns, options become limited for most corn and soybean farmers in Illinois. Many farmers must look to using winter-hardy covers, such as cereal rye.
There is no specific seeding rate that is correct and there are many factors to consider. First, it is important to look specifically at the goal of the cover crop, seeding method, and cash crop rotation. Also, how quickly you can plant after harvest affects decision on seeding rate. Some of the other considerations not addressed will be the weather of that year, soil conditions, if the cereal rye is part of a blend, as well as seed cost and quality.
Example of a drilled cereal rye plot around 40lbs per acre. Picture taken March 31, 2021 in Shelby County, rotating to soybeans.
The first consideration is the goal of the cereal rye seeding. Common goals of farmers include reducing nutrient loss, gaining weed control, controlling erosion, grazing, and building soil health. Ahead of a soybean crop, a seeding rate of 50 to 60 pounds per acre is very common and will be adequate for general soil health gains, reducing nutrient loss in tile lines, controlling erosion, and it ultimately will give some increased weed control. If specifically targeting better weed control, many farmers will increase rates to 80 pounds per acre or more to crowd out weeds and provide more allelopathic control of many weed species. Farmers looking to graze livestock on cereal rye will usually look to increase rates up to 80 to 120 pounds per acre to maximize tonnage and quality. Rates can also be increased if the ground has a significant erosion concern.
Example of using cereal rye in beans for weed control: cover crop material left on the surface provides weed control between the row.
The second consideration is the type of cash crop in the spring following the cover crop. It is important to understand the management needs of a corn crop following cereal rye before using this system. Since cereal rye is a grass species that can produce a large amount of biomass in the spring, caution should be taken since corn is in the same grass species as cereal rye. Cereal rye before corn should only be used once a farmer has some experience with cover crops and can take the proper steps with nitrogen management, spring burndown, and planter adjustments. However, most farmers who are successful with this system start by keeping their seeding rates to around 25 to 35 pounds per acre to help hedge against excessive biomass in the spring. Ahead of a soybean crop, there is less concern about too much biomass since soybeans are a legume and many farmers are working to maximize biomass for their goals.
The third consideration is the seeding method. The gold standard for cover crop application tends to be a grain drill, and this serves as a general base line to compare seeding rates with other seeding methods. Applications that do not have direct seed to soil contact will have fewer seeds germinate and therefore there should be an increase in seeding rate by 25 to 50 percent for an equivalent stand to a drill (depending on conditions). These indirect seeding methods include late season overseeding with an airplane or high clearance seeder, and broadcast applications after harvest without incorporation. Broadcast applications that have the seed incorporated in the soil with vertical tillage or disking will still lose some seed due to either being placed shallow or deep. It is a good idea to increase rates by 10 to 25 percent to ensure the desired stand. Growers who are utilizing row crop planters (usually on 15-inch rows) are often looking at reducing seeding rates compared to a drill (often below 40 pounds per acre).
A drill is one of the most common application methods and provides great seed to soil contact and ground coverage.
Finally, the final consideration is the calendar date. Cereal rye can produce many tillers in the fall. Tillering will increase the overall biomass and can help compensate for lower seeding rates. The earlier the cereal rye is established in the field the more it will tiller. Therefore, the earlier the rye is seeded, the lower seeding rate one can get by with and achieve similar results. Additionally, if less biomass is desired in the spring, (ahead of a corn crop for example) consider planting a little later to avoid as much tillering. The effect of tillering is highly variable depending on weather and variety of cereal rye; a good rule of thumb would be to add 10 pounds of rye seed for each month to compensate for less tillering. For example, if 40 pounds of rye was seeded in September and created the desired result, seeding 50 pounds in October and 60 pounds in November would help to compensate for less tillering later in the year and give similar results come spring.
Example of cereal rye plant with 10 tillers. Tillering will increase the overall biomass and can help compensate for lower seeding rates.
Some quick notes on items not discussed in depth. Always look at the seed tag to check for good germination. Low germination will require the seeding rate adjusted up to achieve the same results. Most cereal rye sold commercially will have a germination of 85 percent or better. Additionally, make sure to take note of the seeds per pound. Seeding in terms of “pounds per acre” is important, but the goal really comes down to “plants per acre”, which is derived from the germination percentage of the seed, the seeds per pound, and pounds applied per acre. Also, if involved in a cost share program of any kind, make sure to check if there are specific requirements for seeding rates either in pounds per acre or a requirement for Pure Live Seed, (PLS), per acre.
Counting plants per acre- This gives an indicator of how successful application, rate, and timing all played in the establishment of your cover crop. As well as determining if we are accomplishing our soil health goals!
