July 23, 2024

Early soybeans set stage for cover crops

SPRINGFIELD, Ill. — Soybean planting is well ahead of the five-year average through mid-May and provides an opportunity to consider cover crops.

John Pike, agronomic consultant and researcher at Pike Ag, Marion, spoke of developing a system to successfully manage soybeans and cover crops in a breakout sessions at the Illinois Soybean Association’s Soybean Summit.

Pike said the majority of cover crop implementation problems he’s heard of were a result of the cover crop being treated merely as just another input.

“We’re not treating the cover crop as a whole system to work around. That doesn’t mean we need to trade in all of our equipment and retool everything, but there’s a certain amount of flexibility and coordination amongst the whole system that we need to keep in mind to make these things work,” Pike said.

Part of the system as a whole is planting soybeans earlier, a move that many farmers were able to do this spring.

Early planting sets up the potential for higher yields. On the back end, earlier planting also means an earlier, more efficient harvest.

Early soybean harvest widens the window for cover crop establishment, improving winter survival, provides the potential for more diverse cover crop mix and offers more options for better cover crop system ahead of corn.

Nutrient Management

Then there’s the nutrient loss reduction part of the cover crop system.

Pike has been involved in research programs focusing on nitrogen management, particularly in southern Illinois where he coordinates the project.

He referred to nutrient loss research conducted by Lowell Gentry, University of Illinois principal research specialist in agriculture.

The research, funded by the Illinois Nutrient Research and Education Council, found higher nitrate losses from soybean fields compared to corn fields between Sept. 1, 2018, and May 1, 2019.

“Every year is different. There will be a lot of variations throughout the state and a lot of different things going on, but we can have greater nitrate loss out of soybeans than we can out of corn fields in some years,” Pike said.

“We can potentially capture those nutrients and keep them there for the corn following the soybean crop. This all fits in as part of the big picture in our systems approach and into the Illinois Nutrient Loss Reduction Strategy. We’ll do a better job of preserving our soil resources and better manage the water that runs out of or off our fields.”

Seeding Date

“Do everything you can to get the cover crops planted/established as early as possible. The more the crop is developed going into winter increases survivability and potential benefits,” Pike said.

He showed field trial results from a study in southern Illinois that found the total nitrogen uptake of rye cover crops planted Oct. 1 was about 160 pounds per acre through March 15.

The nitrogen uptake for rye planed Oct. 15 was about 130 pounds, and Oct. 30 planted rye had a nitrogen uptake of about 70 pounds per acre through March 15.

“As we move later, we’re still getting ground cover and erosion control, but we’re not saving the nitrate loss that we could have with an earlier planting date,” Pike said.

Avoiding Failure

Pike noted several potential causes of cover crop failure.

Herbicides or moisture can cause establishment failure.

“A post-applied residual herbicide program can do just as good a job of controlling our cover crop that we had planted in the fall as it can controlling waterhemp during the season,” Pike explained.

Moisture can be more of a problem when aerial seeding. It is advantageous to drill the cover crop seeds for good establishment.

Another potential cause of failure is using a seed variety that is not well suited to the region. Purchase seed from a source that “knows” their seed.


Nitrogen management in corn has been a big issue in terms of the ability of the cover crop, especially a grass cover crop, to tie up nitrogen.

“Cover crops do a good job of sequestering nutrients and protect them from loss; we also need to manage that when planting corn into a nitrogen-deficient environment. We can make up for that but we need to front-load some early nitrogen to get through that,” Pike said.

The carbon/nitrogen ration needs to be considered when planting rye straw or any grass crop that the corn is planted in to.

“The more nitrogen is going to be taken up, the more tightly that nitrogen is going to be held in the biomass. If we can get some mixes like hairy vetch, clover or something else, anything that we can do to diversify with the rye cover crop so tying up the nitrogen is less of an issue,” Pike continued.

“We can have oats and radishes and mix with rye to get a good covering quick and some other cover crops that would survive. We’d have good cover early in the fall that winter terminates. That biomass would create protection, and then something like clover or vetch in the mix can over-winter.”

Yield Benefits

Pike has conducted precision planted cover crop trials for several years with Ralph “Junior” Upton, a Springerton area farmer. The cover crops are seeded with a drill as early as possible. Upton has been using cover crops in his no-till system for many years.

“Last year was the fifth year of the cover crop trial. Every year corn yields with any combination of cover crops have been better than just no-tilling without a cover crop. That shows that there’s something to be gained by having cover crops in the mix,” Pike said.

Improving soil health with a cover crop system doesn’t happen overnight.

“That’s another misconception that we have that in order to get any benefit or return from cover crops it takes three to five years out. With the right management, the right program and tweaking these things a little bit we can see better results right out of the gate,” Pike said.

“Small improvements can work together to make substantial movement, something as simple as residue distribution out of the back of combine. Evenly distributing residue out of the combine can go a long way to help make the field more uniform, we’ll get better results out of our cover crop.”