Cover Crops
Table of Contents
There are two kinds of cover crops. Cover crops planted along with the permanent seed mix are called nurse crops or companion crops. Those planted by themselves pending a better time to plant the permanent mix are referred to as temporary seedings or stabilizer crops.
Cover crops help hold the soil and are recommended on slopes 3:1 or greater. Oats Avena sativa, annual rye Lolium multiflorum* and winter wheat Triticum aestivum are excellent cover crops because they are inexpensive, easily established and not overly competitive.
Recommended nurse crops/companion crops (planted with the native seed) — per acre
Spring
- 1.5 bushels oats or
- 1 bushel oats and 5 lb. annual rye
Summer
- 2 bushels oats or
- 1 bushel oats and 10 lb. annual rye
Fall
- 30 lb. winter wheat
Recommended Temporary Seedings/Stabilizer Crops (native seed to follow in the spring) — per acre
Summer
1 bushel oats plus 10 lb. annual rye and one of the following warm-season species:
- 5 lb. piper sudangrass
- 10 lb. millet (Japanese or Pear varieties)
- 30 lb. sorghum (grain or forage)
Fall
- 20 lb. annual rye or
- 60 lb. winter wheat
Caution: For native plantings, winter wheat is preferred over winter rye. Winter rye is taller, more persistent and possibly allelopathic, chemically inhibiting the growth of wildflowers. There are many kinds of rye: annual rye (Lolium multiflorum); perennial rye (Lolium perenne) and winter rye, cereal rye and grain rye (all names for the same plant, Secale cereale). Do not seed piper sudangrass, millet or sorghum too heavily. One good rain can cause mass germination. Piper sudangrass may cause concern among landowners as it is sometimes confused with shatter cane.
Cover crop conversion chart
| Species | Pounds in a bushel | Seeds in an ounce | Seeding at 1 bushel/A results in |
|---|---|---|---|
| Oats | 32 | 910 | 10 seeds per square foot |
| Winter wheat | 60 | 937 | 20 seeds per square foot |
| Annual rye | - | 12,710 | Seeding at 10 lb./A results in 46 seeds per square foot |
Cover crops are as much for public perception as they are for erosion control. Having your plantings turn green in a timely fashion is essential for a program’s success.
-Joe Kooiker, Story County, 2024
We use a bushel per acre of winter wheat as a nurse crop when dormant seeding with a hydroseeder. In the spring when hydroseeding, we use a bushel of oats if the soil prep, soil moisture forecast are appropriate. We may continue to use oats through summer in good soil that’s adequately prepped and if moisture is in the forecast. We will blend in annual rye and/or even pearl millet or may substitute the oats for these species as soil conditions and forecast become less favorable.
-Jim Uthe, James Devig, Dallas County, 2024
In addition to increasing our native seed rate on very steep slopes, we also increase our cover crop rate, we essentially do this by applying more material out of the hydroseeder as concern for erosion increases.
-Jim Uthe, James Devig, Dallas County, 2024
In typical Iowa soils, fertilizer and plant growth hormones aren’t needed. However, we’ve used various growth stimulants along with starter fertilizers and various other amendments on steep slopes with poor soil, and have had very good results. It’s cheaper to quickly establish a cover crop than to spend the time and resources repairing or redoing a project. It’s also good PR with the engineering staff and public to see a quick green-up. Again, we only use this practice on areas of very poor soil with a lot of erosion potential, or to protect a high-dollar project.
-Jim Uthe, James Devig, Dallas County, 2024
The majority of our regraded slopes are steep. I regularly use 2.5 bushels of oats, 6 lbs. of annual rye and 3 lbs. of timothy along with the permanent seed mix. This provides a better chance of stabilizing the slopes while the permanent seeding establishes, and I haven’t noticed any detrimental effect to the planting’s long-term success.
-Linn Reece, Hardin County, 2011
The nurse crop can be added to the slurry in the second pass with good success. Wheat and oats are very difficult to keep in suspension in pure water, so it’s better to include in the mulch in the second pass.
-Wes Gibbs, Jones County, 2024
On large, contracted projects we fertilize the cover crop to DOT specs; the flush of weeds has usually subsided by the time we plant natives in the fall or following spring. We do not use fertilizer when hydroseeding.
-Wes Gibbs, Jones County, 2024
When broadcasting in light tillage we use some, but sparingly. I wouldn't recommend fertilizer with natives, but it does help cover crops planted in nutrient-deficient soils.
-Wes Gibbs, Jones County, 2024
I have used several different cover crops from oats, winter rye, buckwheat, perennial rye, and going to experiment with sorghum grain and Sudan grass, and mellites for summer ditch cleanouts and other projects. I will utilize these species because they are drought tolerant, and they are fast growing. These are things that we are all battling with in the ROW’s. For rates of current use – oats 30 to 40lbs/ac, winter rye 1bu/ac, perennial rye 10lbs/ac I keep this thin with the rye and oats to get some fast green on projects but then the natives can out compete them in the long run, and buckwheat 10 to 20lbs/ac on summer projects keep it on the lighter side with oats and perennial rye because they have a large leaf and can cause shade out of natives until a mowing on a first year seeding. I like buckwheat in my summer blend because it is fast growing and drought tolerant.
Most of these cover crops are broadcast seeded, however I have done some drilling and mixed it in with the hydroseeder as a method of seeding. I have seed success with all application methods.
-Griffin Cabalka, Black Hawk County, 2024