How to minimize cover crop risks

The myriad of cover crop benefits are well known: they slow erosion, build soil health, smother weeds, enhance nutrient and moisture availability, and bring a host of other benefits to the farm. Yet there is still hesitancy for growers to adopt cover crops. 

In a recent University of Illinois FarmDoc webinar, Precision Conservation Management (PCM), the conservation program of the Illinois Corn Growers Association and Illinois Soybean Association, offered a detailed look at cover cropping systems in corn and soybean that have been most profitable in Illinois — and how they were managed. 

Only 6% to 9% of agricultural fields in Illinois utilize cover crops. What makes farmers hesitate to add cover crops to their rotations? Laura Gentry, Director of Water Quality Science for PCM said there are several legitimate reasons that farmers may hesitate to grow a cover crop. 

“The number one reason is that cover crops do not produce a harvestable product that farmers can sell. It costs money to buy the seed, chemicals and/or the equipment to manage the cover crop,” Gentry says. “Planting and terminating activities also require individual time and labor expenses of the farmer and the farm operation. Finally, and very importantly, growing cover crops does introduce some risk of yield reduction to the cash crop.” 

There are still compelling reasons to use cover crops. “Most farmers use cover crops as a defensive strategy,” says Gentry. “They’re using cover crops to protect their fields from soil erosion and from nutrient losses. And they’re also thinking about cover crops as protection from government regulations that may potentially be disruptive, limiting, and complicating on a day-to-day basis for farmers, if those come to fruition.” 

Cover crops ahead of soybeans

“Cereal rye is the species of choice for a cover crop ahead of planting soybeans," says Gary Schnitkey, farm management extension specialist with the University of Illinois. “The seed is relatively low cost, easy to establish, and overwinters well.” 

Cereal rye is typically planted after corn harvest and can be broadcast (usually with fertilizer), broadcast with a vertical tillage pass, or drilled. “Adding the tillage pass generally adds $11 to $12 per acre, so you have higher costs, but you have better establishment of the cover crop,” explains Schnitkey. “Drilling is the most expensive, takes the most time, but results in a good establishment.”

There is a yield advantage to planting soybeans early, and planting soybeans ahead of corn in April is common for the most profitable cover crop farmers in PCM. Cover crop termination can be done ahead of planting or after planting soybeans.

“Terminating the cover crop before planting reduces the risk of competition with the soybeans, but may also decrease weed control,” says Schnitkey. “Many farmers talk about the increase in weed control as one of the benefits for planting cover crops. Terminating cover crops after planting gives a higher chance of eliminating one herbicide pass.”

PCM found that when using a cover crop ahead of soybeans, there was no statistical difference in soybean yield compared with fields without a cover crop. Lower direct costs in cover crop systems generally come from reduced herbicide cost. However, yield differences and reduced herbicide costs do not entirely offset the cost of cover crop seed and planting. 

Precision Conservation Management average results for cover crop planted ahead of soybean (per acre) for high-productivity farmland in central Illinois, 2019 to 2022.
	Cover Crops	No Cover Crops	No Cover Crops
Tillage	No-till	No-till	One Tillage Pass
Yield (bpa)	67.3	67.8	68
Gross Revenue  ($ per acre)	$783	$783	$786
Direct Costs	$177	$189	$174
Power Costs	$73	$75	$87
Overhead Costs	$33	$33	$33
Cover Crop Costs	$25	$0	$0
Total Non-Land Costs	$308	$297	$294
Operator and Land Return	$475	$486	$492

Cover crops ahead of corn

Cover crops ahead of corn are more challenging than ahead of soybeans. Species selection and seeding is less straightforward. “There are three systems that do show promise. The first uses clover seeded before harvest, second is cereal rye after harvest, and, finally, winter terminal cover crops,” explains Schnitkey. 

Schnitkey explained that planting clover after soybean harvest often does not result in a good stand, causing many farmers to plant cover crops earlier into standing soybeans by aerial applications. The aerial application and the clover seed cause planting costs to be higher than other options. “The advantage of this system is that clovers not only sequester nitrogen, but are nitrogen producers themselves, which may become available for the corn crop later.” 

A cover crop of cereal rye ahead of corn reduces costs but introduces nitrogen issues in the spring with the following corn crop. While the cereal rye sequesters nitrogen (keeping it out of streams and other water bodies), it also likely causes the nitrogen to be unavailable to the corn crop, requiring fertilizer to be placed with the corn at or before planting.  

Schnitkey outlined that winter terminal cover crops such as oats and turnips are low in cost and generally are easy to implement. They are planted in the fall and terminate over the winter. “The disadvantage to this system is there’s no spring growth of the cover crop for the added benefit of weed control and nitrate sequestration.” 

PCM data has found that maintaining yields for the corn crop is a challenge with the overwintering cover crop species. Schnitkey did note that there was no yield difference between winter terminal cover crops and no cover crops, but the added cost of the cover crop resulted in a lower net return. 

Precision Conservation Management average results for cover crop planted ahead of corn (per acre) for high-productivity farmland in central Illinois, 2019 to 2022.
	Winter Terminal Cover Crops	Overwintering Cover Crops	No Cover Crops with One Tillage Pass
Yield (bpa)	218	215	217
Gross Revenue ($ per acre)	$1,087	$1,066	$1,070
Direct Costs	$436	$451	$441
Power Costs	$116	$114	$115
Overhead Costs	$40	$40	$40
Cover Crop Costs	$30	$26	$0
Total Non-Land Costs	$622	$631	$596
Operator and Land Return	$465	$435	$474

Managing costs of cover crops

Keeping costs low is the key to being profitable with cover crops. 

“So what we have to do is find a revenue source for covering that cost. And there are several of those,” says Schnitkey. The added cost to plant cover crops can be offset by reduced herbicide costs, as well as funds from programs like EQIP, CSP, PCM, and emerging carbon markets. 

Gentry shared that another program that can be of benefit is Farmers for Soil Health. It covers 20 states and any farmer within the region can enroll. “This program is a three-year, tiered opportunity for new cover crop fields. As long as you didn’t use a cover crop the previous year, the field is considered a new field in Farmers for Soil Health opportunity,” explains Gentry. “Farmers receive $25 the first year, $15 in year two, and $10 in year three for what's considered new cover crop acres.” 

The PCM program is available to farmers in Illinois, Kentucky, and Nebraska. For more information on PCM and the full report on managing risks with cover crops, visit https://www.precisionconservation.org.