Cover crops can benefit soil health and improve corn and soybean yield potential, but it's important to make sound, informed decisions when integrating them into a row crop rotation.
Cover crops are species usually planted as a mixture to improve soil physical and biological health and ultimately help boost productivity of cash crops, according to the USDA Natural Resources Conservation Service. They benefit soil through erosion prevention, nutrient management, improved water availability and pest control.
For row crop farmers, cover crops are typically planted in the fall. Initial cover crop establishment can help manage soil nutrients as a way to prepare for the following growing season.
"Nitrogen (N) management will probably be a major factor in your cover crop decisions for the corn-soybean rotation. A fall-planted grass or small grain will scavenge leftover N from the previous corn or soybean crop," according to a report from USDA Sustainable Agriculture Research & Education (SARE).
In addition to the soil condition benefits, a cover crop can improve row crop yields and a lead to a decline in the amount of fertilizer necessary to achieve those yields.
"Per-acre cost is offset if soybean yields increase by 2.5 bushels per acre [based on a long-term soybean price of $10.40/bushel]. Corn yields increase by 5.8 bushels/acre [based on a long-term corn price of $4.40/bushel]," says University of Illinois Extension ag economist Gary Schnitkey in a Farmdoc Daily report, Costs and Benefits of Cover Crops. "This yield increase would happen in the year after soybeans have been planted into the cover crop. Nitrogen application rates would have to be decreased by $70 per acre.”
Find the right crops
Selecting the right cover crop mix for your operation starts with identifying your needs and determining which species will best meet them. Maximizing yield in your cash crops should take priority, and it's important to select a cover crop mix based on your specific needs.
"One of the biggest challenges of cover cropping is to fit cover crops into your current rotations, or to develop new rotations that take full advantage of their benefits," according to SARE. "You should devote as much planning and attention to your cover crops as you do to your cash crops."
Here are some common cover crop species, along with their intended benefits, according to NRCS:
- Black oat: Winter annual for weed management and forage.
- Brassicas: Include forage radishes, rapeseed and turnips. For soil preparation, hydraulic conductivity and soil fertility.
- Buckwheat: Summer or cool-season annual for ground cover, weed management and soil fertility.
- Cereal Rye: Cool-season annual grass for forage, erosion control, wildlife habitat and weed suppression.
- Crimson Clover: Winter or summer annual for ground cover and nutrient management.
- Cowpea: Summer annual for forage, ground cover and wildlife habitat.
- Field Mustard: Annual or biennial forb for forage, ground cover and as a biofumigant.
- Hairy Vetch: Winter annual for soil fertility, moisture conservation and weed management.
- Lablab: Annual summer for ground cover, forage and wildlife habitat.
- Oilseed radish: Annual/biennial for ground cover, soil preparation and cultivation.
- Pea: Annual for ground cover and soil fertility, namely adding nitrogen to the soil.
- Pearl Millet: Summer annual for soil fertility, erosion control and weed management.
- Pigeonpea: Perennial summer crop for forage, soil fertility and wildlife habitat.
- Sorghum: Drought-tolerant summer annual for ground cover and soil preparation.
- Sudangrass: Summer annual for weed management, soil fertility and ground cover. Often hybridized with sorghum.
- Sunn hemp: Annual summer crop for forage, soil fertility and wildlife habitat.
"Species selection requires answers to questions like: 1) What’s the goal of using the cover crop, 2) will the cover crop grow and overwinter, 3) how will it be planted and terminated, and 4) what is the current and subsequent crop?" according to Iowa State University Extension agronomist Mark Licht. "These answers will guide you to winter cereal grains, spring cereal grains, legumes, brassicas, or perennial grasses and legumes that are commonly used as cover crops."
Establishing your crop
Once you've selected your cover crop species and where they'll be planted, look closely at your machinery lineup and determine the most cost-effective way to establish your stand. Cover crops can typically be planted in different ways, from small grain drills and conventional planters to "air seeding" with aircraft usually used for chemical applications. A strong stand establishment strategy takes into account both the machinery you'll use and what it will cost.
There are four primary ways cover crops are sown, according to Michigan State University Extension:
- Broadcast by air. Applying from a broadcast seeder on an airplane works well for larger seeds, like rye and wheat. This allows for effective overseeding or planting into wet soils.
- Broadcast by ground. Applying from a ground-based broadcast seeder helps ensure an accurate, more consistent seeding rate. It's important to make sure you take seed weights and size into account when planting this way.
- Incorporation. Using a shallow tillage tool along with a broadcast seeder can provide valuable soil-to-seed contact and help incorporate seed better at planting, helping establish a strong stand early.
- Drilling. Like incorporation, air drills normally used for small grains can help establish a cover crop early. Using a drill to plant cover crops also works well in no-till management systems.
“Timing of seeding will vary depending on the cover crop species, type of planting method, and fall frost dates, among other factors,” Licht says.
Terminating cover crops
Once your cover crop mix has been planted, grown and performed its intended purpose, termination is the next step. Herbicides, winterkill and tillage are the primary ways cover crops are terminated.
“The effectiveness of a herbicide at terminating a cover crop depends primarily on the cover crop species and growth stage, the herbicide and rate used, and the environment,” according to an Iowa State University Extension Integrated Crop Management report. “Tillage is an option but may fit better into some operations than others. Multiple tillage passes may be necessary to terminate the cover crop, which can negate the benefits the cover crop is providing to soil health and could result in erosion.”
Costs and returns
Specific costs to manage a cover crop include seed, herbicide, insecticide, fertilizer, machinery, labor and land. Those individual costs vary depending on a few key factors, according to Schnitkey.
"The costs associated with a cover crop will depend on many factors including the previous crop, next crop, tillage system, pesticide practices, cover crop species planted, and cover crop planting method," he says. "Most of the costs associated with the cover crop will be in its establishment, which includes planting and seed costs."
Using an example of a cereal rye cover crop drilled into standing corn stalks in a corn-soybean rotation, Schnitkey says the initial establishment cost is around $20/acre, with additional in-season treatments and termination adding between $15 and $25/acre. Though burndown herbicide applications can eliminate the cost of additional tillage passes for termination, no-till typically leads to a higher overall per-acre cost for a cereal rye cover crop.
"A no-till system would be expected to have higher costs of $25.60 per acre compared to $15.10 per acre for minimum tillage. This difference in cost is largely due to the reduced costs moving from minimum tillage to no-till and cutting out two passes in the field," Schnitkey says. "Adopting cover crops in a no-till situation likely is easier to implement because fewer production practices need to be changed than in a minimum tillage scenario."
See another example of a cover crop cost-return budget (from Kansas State University Extension AgManager.info).
Financing cover crop machinery
Because of the many different cover crop mixes and ways to plant and manage them, machinery needs vary by operation. In some cases, purchasing new implements, like a seed drill, may be necessary. But, in many cases, tools like broadcast seeders can be added to tillage equipment. That makes the financing process much simpler, says AgDirect Territory Manager Scott Welden.
"Farmers needs to ask themselves if they need to change their line of equipment or just make a few modifications to existing equipment to be able to embrace and build a comprehensive cover crop program," Welden says. "If a farmer has the ability to make modifications and add an air seeder to a tillage tool, it is much easier to finance."
Welden likens such a strategy to purchasing a bed cover along with a new pickup. That add-on doesn't require separate dedicated financing and is essentially bundled with the pickup purchase. With AgDirect, the same applies for purchasing an air seeder attachment along with an upgraded tillage tool.
"It may change the price, but it's the same deal. We are very open to financing cover crop seeders this way. It doesn't complicate the process," Welden says. "If I'm going to pull the seeder with the tillage tool I'm using to both till and incorporate the seed, it's the same field operation, and they're both intended to manage crop residue.
"AgDirect is very familiar with this, and there's no additional paperwork. It can be part of the same transaction," he adds. "We make it very easy."
If you're interested in integrating cover crops into your operation and would like to learn more about financing the machinery to get started, contact your nearest AgDirect representative.