The Pros and Cons of Cover Crops
By Brogan Schanz, Field Program Representative at SWOF
A cover crop is a plant grown to maintain vegetation on the soil when traditional crop types are not present. Though they can be, cover crops are not typically grown as cash crops. There are many benefits to utilizing cover crops in your operation. Depending on the species and type, cover crops can protect and improve soil health by managing erosion, stabilizing nutrients, and more. But there is also a learning curve and financial challenges to successfully implementing this farming method. Below we explore the key pros and cons of the cover crop system.
Pros:
Erosion Control – With soil coverage for potentially six months’ time, a very dense layer of vegetation will decrease the speed of rainfall before it even hits the ground, lessening the impact and surface runoff.
Building Soil Structure – The abundant root networks of cover crops also helps keep soil firmly in place, providing the perfect habitat for macrofauna to thrive. These small creatures such as earthworms, centipedes, slugs, and spiders play an important role in soil aeration and moisture retention because of their burrowing and mixing activities.
Building Soil Organic Matter – Since cover crops aren’t commonly harvested, they decompose into the soil when their growing cycle reaches its end, thus infusing organic matter into the soil. This serves as a kind of makeshift manure or compost without having to haul and spread manure.
Reduced Weed Pressure – As a competitor for nutrients and space, cover crops hinder the growth of noxious weeds such as Waterhemp. The allopathic effect of decomposing rye can also serve as a germination inhibitor, furthering weed control. In cases where cover crops are allowed to grow to more substantial heights, they form an almost impermeable layer above the soil that blocks sunlight from contacting the soil and allowing weeds to germinate.
Reduce Compaction – Cover crops increase soil volume and porosity, reducing its density. Certain cover crops such as tillage radishes or turnips, called Brassicas, have deep tap roots that break up soil compaction and can capture nitrogen remaining in the soil after a crop harvest.
Moisture Retention – By maintaining soil structure via root mass, cover crops will hold and filter water and keep nutrients in the soil. Cover crops also diminish the amount and rate of unwanted water runoff by helping the soil absorb and retain water.
Cons:
Insects – With a green crop in the ground longer, cover crops can attract both beneficial insects and pest species. (This can be especially true for a field in early spring with little other cover, such as rye.) Wireworms, Seed Corn Maggot, Black Cutworms, Armyworms, slugs, and other species all thrive on green matter that cover crops provide, particularly grassy species. Seed Corn Maggot adult flies can be attracted to rotting plant materials, such as terminated cover crops. And fields that receive regular manure applications serve as ideal egg laying locations.
Solution
For best insect and disease management, be weary of planting cover crops in front of a cash crop of the same plant family. For example, a clover cover crop before soybeans can pose risks as both are legumes that are susceptible to the same pests and diseases.
Also know your insect and disease life cycles. Several Midwest universities track Armyworm and Black Cutworm moth flights into the upper Midwest each spring. Monitor their websites for information about when to begin scouting for larval feeding in corn and small grain fields.
Poor crop sequence planning can cause pest spread – insects and disease – due to the use of successor plants that may be susceptible to pests harbored in the cover crop. Utilizing crop rotation will usually help minimize this problem.
Disease – Allelopathic compounds are water soluble compounds released into the soil by certain cover crop species (for example, winter rye and to a lesser extent other small grains, brassicas, sorghums, and millets) that suppress the germination of small-seeded species. This can be a desirable characteristic of cover crops if your goal is weed control, but allelopathic compounds can also suppress cash crops as well.
Pythium root rots and Fusarium can be transferred from Cereal Rye to a following corn crop in the right conditions. And some cover crop species, including clovers, peas, and hairy vetch, are alternate hosts for Soybean Cyst Nematodes.
Solution
All of these situations are usually avoidable with timely termination of the cover crop. Have a plan. Three days of warmer temperatures with adequate moisture, and rye will go from manageable to becoming a problem and effective termination can be questionable. One should also potentially avoid using cover crops with allelopathic properties in rotations before planting small-seeded crops, such as alfalfa, clover, and other forage species. Medium-sized seeded crops may also be affected, such as flax. Although the occurrences of witnessing allelopathic symptoms in these situations are rare, it is a possibility.
Cost - Other factors to consider include the price of seed and the likely extra chemical costs in your first pass of chemicals.
Solution
Your cover crop should serve as an effective weed suppresser, therefore reducing the amount and cost of herbicide needed. Fields laying bare or fallow for long periods of time could give weeds a chance to gain a foothold. Even some herbicide-resistant weeds, like Waterhemp, can be largely prevented by the extensive root system of Cereal Rye. Although one may incur the additional costs of ensuring adequate glyphosate rates in a burndown pass, the end game results in less herbicide use year over year as the natural allelopathic effect of certain cover crops diminishes the presence of noxious weeds.
Admittedly yes, there are risks involved. But with smart planning and proactive measures, cover crops can be a powerful, offensive tool in building your farm’s resiliency by improving soil health, managing moisture, stabilizing nutrients, and more. If you’re nervous about taking on this method, the Soil and Water Outcomes Fund® is also here to help. Our team of field program representatives are trained agronomists, specializing in conservation farming practices. We can help you make decisions about what cover crops to plant and when based on your operation’s growing rotation. Farmers participating in our program also earn financial incentives for the environmental outcomes generated by adopting this on-farm conservation practice. In 2022, enrolled farmers earned an average of $34/acre. Visit the Farmer Resources page of our website to learn more or contact us today with questions at contactus@theoutcomesfund.org. Enrollment is currently open across several states.