Are Diverse Cover Crop Mixtures Right For You
By Liz Ridenour, Extension Intern Amanda Grev, Forage and Pasture Extension Specialist Jeff Semler, Principal Agriculture Agent
Although it’s difficult to imagine with recent summer heat, fall is fast approaching and now is a good time to consider which winter cover crop species works best for your operation. Cover cropping is beneficial to soil health, reducing soil erosion, pest, and weed pressure, savaging nutrients and adding nitrogen for the following cash crop. While winter cover cropping with a monoculture such as a cereal grain harvested for forage is a common source of extra revenue between cash crops, cover crop mixtures of multiple species have additional benefits which make them more than worth considering as an option for your operation this winter.
Benefits of Multiple Species:
Plant diversity is a key principle of soil health. The more diverse a field is in terms of plant life, the more diverse the root systems in the soil are, which fuel the soil’s microbial life and allows for less erosion and greater retention of water. Species groups of plants such as brassicas, legumes, and cereal grains all have unique benefits which may be magnified when planted in a mixture, but each also has specific drawbacks, making complementation in a seeding mixture key to a healthy cover crop mixture.
In terms of cover crop benefits, legumes with their nitrogen-fixating abilities often get the spotlight, and this makes sense, as low nitrogen levels in the soil limit plant growth, and when planted as a cover crop, legumes do provide a source of nitrogen for the following cash crop. However, excessive nitrogen levels can increase the growth of weeds and contribute to nitrogen leaching. Complementary mixtures of species with different nitrogen acquisition strategies, such as a pairing of legumes with brassicas or grasses, is beneficial in fixating the right amount of nitrogen for crop growth while avoiding excess nitrogen.
Cover crop mixtures can also have benefits beyond nitrogen fixation. Species with complementary growth periods ensure that green cover extends longer in the winter season, reducing erosion and benefiting the soil until spring planting of the cash crop. Brassicas such as radishes and turnips break up soil compaction with their dense and fast-growing roots, while flowering species attract pollinators and beneficial insects which act as predators for pests. However, flowering plants are often prolific re-seeders, and this should be considered before these species are integrated into a cover crop mixture. Cover crop stands can provide a winter habitat for beneficial insects, but they can also do so for pests, and it is important to maintain crop rotation that takes into account both pests and diseases which can be shared between cover crops and the following cash crop.
How to Build a Complementary Mixture:
Building a complementary mixture can be challenging, but these steps can be a good starting point:
- Choose three desired cover crop services (i.e., nitrogen fixation, biomass production, etc.) for your farm or for that specific field.
- Identify the planting and termination dates for that cover crop, which determines the growth window of that crop. For example, for early planting in the spring, you may choose a species which winterkills, making termination unnecessary, but these species generally have to be planted in late summer/early fall. Using a mixture of winter-killed and winter-hardy species will increase uptake of nitrogen, control erosion, and reduce weed pressure by maintaining a living cover for a longer period.
- Pick a specific set of cover crop species with your desired services adapted to your growth window. Complementary growth periods among this set of species are especially desired, as well as complementary nutrient acquisition strategies. If one or more species have major drawbacks or do not complement the other species, drop them from your list until you have your desired list of species to plant.
- Determine the appropriate seeding mix and planting method (competitive species should be planted at a lower rate than other species, for example) and get planting!
Termination of the Cover Crop:
Cover crop growth can be terminated by tillage, rolling, or herbicides. In a wet growing season, tilling legumes into the soil may produce slightly greater yields in the crop that follows. However, if the legume residue is left on the surface, it will increase water infiltration and preserve soil moisture in dry growing conditions. In general, the procedures for no-till planting into a cover crop are similar to planting into residues of a previous crop, such as soybeans or corn.
Winter cover crops are a powerful tool for improving soil health, reducing erosion, managing pests, and optimizing nutrient cycling. While monoculture cover crops are effective, cover crop mixtures provide enhanced benefits through plant diversity, complementary growth periods, and balanced nutrient strategies. By integrating legumes, brassicas, and cereal grains into a well-planned mixture, farmers can address specific field needs while fostering long-term sustainability.
Taking the time to select the right species, plan for planting and termination dates, and tailor the seeding mix to your operation ensures that your cover crop will contribute to healthier soil, better crop yields, and reduced environmental impact. As fall approaches, now is the ideal time to prepare for a productive winter cover cropping season that supports both your farm and the environment.
Resources:
- Winter Annual Cover Crops | NC State Extension Publications
- Making the Most of Mixtures: Considerations for Winter Cover Crops
- Using Cover Crops to Direct the Soil Microbiome
This article appears in August 2026, Volume 17, Issue 5 of the Agronomy News.