Figure 1. Spring rye cover crop growth in field near Sioux Falls, SD.
Crop rotations with small grains in the sequence allow for an adequate seasonal window to establish variety of cover crop blends following grain harvest. However, producers with strict corn-soybean rotations are limited in their options for cover crop species, since there is not enough growing degree days left for cover crops to grow after primary grain crop has been harvested. One cover crop that has caught attention and has consistently worked in South Dakota environments where pre-dominant rotation is corn-soybean is winter rye.
About Winter Rye
Winter rye is known for its winter hardiness allowing late fall planting and puts on a rapid growth the following spring. Furthermore, adding a cool season small grain component into a corn-soybean rotation would not only add diversity the cropping system but also help break pest pressures in the field. Winter rye is also known for its inherent ability to suppress weeds because of its allelopathic characteristics, i.e. its ability to produce biochemical compounds that inhibits germination, growth, and reproduction of other plants. On a long term basis incorporating cover crops would also help improve soil health and provide supplemental forage.
Fitting Into Rotation
Considering growing habits of all three crops is essential when determining the order of winter rye within the cropping sequence. Planting rye after corn, and ahead soybeans, seems to be a better fit than to grow rye before corn. This way corn residue provides protection to rye seedlings. In addition, soybeans can tolerate later planting in the spring better than corn which allows rye to accumulate more spring growth. Rye biomass in the spring can be terminated as cover or utilized as forage depending on the farm need. Research conducted in various locations of Southeast SD for the last few years has shown no negative impact on soybean yields when grown on rye cover crop residue. On the other hand corn yield tends to suffer following a rye cover crop which could be due to allelopathic effects of growing rye cover crop or the micro climate created by the rye residue on the soil surface at the time of corn seeding. It is suggested to terminate rye 2-3 weeks prior to corn planting to avoid any negative impact on corn plant health and grain yield.
- Seeding rate is about 40 lbs/ac as a cover crop, however, it can be increased to 75 lbs/ac if weed suppression is the primary objective.
- Aerial seeding can be done during mid to late corn seed-filling stage (early Sept). Research results show that aerial seeded (or broadcast method) rye produces about 80% of the spring biomass of drill-seeded following grain harvest.
- Producers of small grains such as wheat, oat, barley, etc. are suggested not to use winter rye as a cover crop because it may act as significant contaminant or weed in small grain crops.
- As winter rye accumulate rapid growth in the spring, it is a good practice to look out for short or medium term spring weather so that rye can be terminated early when conditions are drier than usual.