Farmers are the ultimate survivors. Their work requires incredible planning, but it also requires creativity. This year, farmers have faced the test of extremely limited rainfall, which has limited overall yield potential. With fall approaching, farmers have an opportunity to invest today for better outcomes next year by planting cover crops. Not harvested like a main crop, cover crops are grown to protect the soil from wind and erosion, as well as create an underground community for soil improvements.
Cover crops offer a wide range of benefits: they “trap” nitrogen left behind from fertilizer in the field, which otherwise may be washed away over the winter. Their residue can help conserve water, improve the quality of soil, suppress weeds, and control erosion. Cover crops can also provide an excellent source of animal feed during periods when drought has reduced forage quality and quantity.
Identifying your cover crop goals and planning is key in any year and is especially critical during drought conditions. This planning not only includes selecting the species of cover crops but also looking at the overall management decisions of planting method and timing, maintenance, and termination of the cover crop. Of all these management decisions, one of the greatest risks to cover cropping is failure to establish. Limited rainfall threatens establishment success, and the choice of method can influence the outcome.
Whether or not your farm is dealing with drought, it will be something you’ll have to take head-on in the future. So, how do cover crops fit into navigating periods of drought? Using cover crops can be a combination of a bodybuilder, bodyguard, and insurance agent all working around the clock to protect your most valuable asset — your soil.
Bodybuilder
Cover crops are going to “bulk up” your land above and below ground. Biomass, or your cover crop's vegetative growth, is going to add organic matter back into the soil as it decomposes. An increase in organic matter improves soil quality and serves as a nutrient source for soil microbes, contributing to an increase in overall soil health and fertility.
Bodyguard
In times of drought, cover crop residue can serve as a protective barrier between soil and the elements. Cover crops can preserve soil moisture by regulating temperature and protecting the surface from evaporation, while increased soil organic matter improves water-holding capacity.
Research has found that greater amounts of biomass at termination lead to greater amounts of weed suppression, by blocking sunlight from reaching the soil and serving as a physical barrier to germination and growth. Along with biomass production, extensive roots of certain cover crop species help hold soil in place to prevent erosion from wind and rain. Cover crops can also reduce nutrient leaching by sequestrating nitrogen, making it available for future crops when residue decomposes.
Insurance agent
Incorporating cover crops into a crop rotation is an effective way to mitigate the potential negative effects of dry periods in future years. However, a good insurance policy is needed to ensure the best management decisions are being made so that the bodybuilder and bodyguard perform at their maximum potential. This begins with identifying cover crop goals and developing a game plan for how to achieve them.
Selecting cover crops in 2024
Most crops need approximately 35-45% soil moisture to germinate, and this is no different for cover crops. Ensuring adequate seed-to-soil contact improves establishment outcomes and reduces seed losses from desiccation. Drilling after harvest increases this contact relative to broadcasting where the seed is left on the soil surface. Incorporating seed into the soil with a drill decreases the chances of seed death from lack of moisture.
Consider species that can grow and produce biomass when planted late in the season. Many species can produce at least 1/2 a ton of winter grazing dry matter. All cereal grain cover crops grow roots when the soil is not frozen. Beyond weed control, nitrogen retention, erosion control, and residue, some farmers grow cover crops for the purposes of grazing and increased forage options. Potential species that can perform well even in dry conditions include cereal rye, winter wheat, triticale, rapeseed/canola, and forage turnips.
Cereal rye can germinate in soil temperatures as low as 34°F and grow when temperatures are above 38°F. This is one of the many reasons why cereal rye is the most widely used cover crop species in Ohio and across the Midwest. It is among the most drought-hardy and generates high levels of biomass and an expansive root system.
Winter wheat can germinate when soil temperatures are as low as 38°F but needs 50°F for growth. Wheat can provide some benefits in terms of weed suppression but is less effective than other cool-season cereals due to lower biomass production. Wheat may reduce sclerotinia and is not an alternative host of sugarbeet cyst nematode, soybean cyst nematode, or root-knot nematode. Wheat is not recommended as a cover crop in rotation with corn due to similar disease and pest profiles. It is recommended to plant wheat after the Hessian fly-free date, even when used as a cover crop.
Triticale is more expensive but germinates and grows like cereal rye, with the forage quality and maturity speed of wheat. Triticale has good biomass production and rooting capability.
Brassica species generally have high drought tolerance. Options for brassica cover crops include rapeseed or forage turnips. Rapeseed germinates in temperatures as low as 36°F but needs 41°F to grow. It germinates with a water weight of 500% of its weight or 0.65 ml of water per 20 seeds. Forage turnip tops die at the first frost (15°F), but the bulb lasts a long time. Forage radish also has high-nitrogen retention, but due to high seed cost may not be the most economical option, except when grazing is desired.
Weed suppression from cover crops is a benefit due to the biomass and ground cover provided by the cover crops. Cover crops are a tool that can reduce the size and density of weeds, and reduce the pressure on herbicides, but not replace effective herbicide programs and applications. In drier conditions, herbicide breakdown is slower than when there is adequate moisture for soil microbial activity. Increased herbicide rates, late applications, and applications of an active ingredient more than once during the season increase the risk of herbicide persistence in the soil, especially in dry conditions. Doing a bioassay before planting your cover crops this year may help ensure success and decrease frustrations if cover crops don’t grow. A bioassay is simply taking a sample of topsoil or a small area of the field in both treated and untreated areas, planting a set number of cover crop seeds, and watering. The percent germination can then be calculated and compared between the treated and untreated areas.
Nitrogen retention
Cover crops can increase nitrogen retention preventing N losses that would otherwise leach from the soil during the fall, winter, and spring months. The cover crop can hold that nitrogen in the biomass and release for use by the following crop. Some cover crops can tie up nitrogen, especially when the carbon-to-nitrogen ratio approaches 25:1 (pre-jointing).
Erosion control and residue retention
While cover crop species mixes can have many benefits, in tough economic times more value might be attained from monocultures of one species, which are more cost-effective and can still provide many benefits. Maintaining a soil ecology that promotes vigorous and sustainable crop production depends heavily on plant diversity, and including cover crops in rotation with cash crops can increase the diversity in the cropping system. They are an important factor in determining the biological diversity of the soil and the microorganisms in the soil and each plant introduced to the soil supports a host of unique bacterium, insects, and organisms.
To increase the overall beneficial soil organisms, it is recommended to implement a diverse crop rotation, which includes the use of cover crops to provide live roots in periods that would otherwise be fallow. Although the state is in a severe drought, it is likely that drilled cover crops can still germinate and grow when planted in dry conditions. Some species have very small seeds that require little moisture to germinate. It will however be important to get precipitation when the seedlings germinate and emerge to achieve sufficient biomass and growth. When planting into dry soil be sure to close the furrow tightly and allow the seed to be protected while waiting for moisture. Additionally, if enrolled in an EQUIP (NRCS) or H2Ohio (SWCD) program, please be sure to adhere to the seeding rate and date requirements for program payment.
Some great resources are:
- Midwest Cover Crop Council selector tool on their website. This will help with a county-by-county reference with planting dates and cropping conditions. The tool is located at https://www.midwestcovercrops.org/selector-tools/.
- Midwest Cover Crop Council Ohio Species Cover Crop factsheets located at https://www.midwestcovercrops.org/ohio-cover-crop-factsheets/.
- National Sustainable Agriculture Research Education (SARE) book, Managing Cover Crops Profitably, located at https://www.sare.org/resources/managing-cover-crops-profitably-3rd-edition/. This is available as a free downloadable PDF, or the hard copy book can be purchased via the website.
- Cover Crops for Weed Management: Herbicide Persistence and Carryover to Cover Crops https://bpb-us-w2.wpmucdn.com/u.osu.edu/dist/7/3461/files/2024/06/Cover-crop-carryover.pdf
- Cover Crops for Weed Management: Establishment https://bpb-us-w2.wpmucdn.com/u.osu.edu/dist/7/3461/files/2024/06/Cover-crop-establishment.pdf