Cover Crop Hits and Misses

March 4, 2017 02:51 AM
Cover Crop

Rye can be 3" tall one day, 6" the next and more than 1' a few days later. When used as a cover crop, rye can compete with cash crops for water, sunlight and nutrients. While rye might be among the most popular of cover crops, it doesn’t mean it’s the easiest to manage. 

When Indiana farmer Jason Wykoff’s use of cover crops created challenges for his cash crop, he didn’t let setbacks deter his goal of improving soil health. He grows cover crops on one-third of his 4,000-acre farm. He plans to eventually convert at least 75% of his acres to cover crops.


&ldquo​;You need to have a plan A, plan B and plan C before you even seed the cover crop,” Wykoff says. “Moments of panic and failures have led us to do a better job of planning.”

For example, during the spring, plan A for Wykoff involves terminating and flattening the cover crops with rollers before planting the cash crop. When weather doesn’t cooperate, plan B could mean the cover crop doesn’t get flattened and Wykoff is forced to plant in less-than-ideal conditions due to shading. If poor conditions persist, it might mean going to plan C, which is planting cash crops later than normal.

“The No. 1 failure I’ve seen is when producers are interested in cover crops and just jump in without knowing what they want to accomplish,” says Paul Jasa, University of Nebraska Extension engineer.

First determine what you want to accomplish. This narrows down the types of cover crops to consider. Common goals include building soil health, preventing erosion, weed control or providing additional grazing opportunities for livestock.

“If you want immediate cover, look for a grass-type crop,” Jasa says. “If you want to build nitrogen then look at a legume like vetch. Want to break up compaction? Find a good tap root like daikon radish. Attracting pollinators? Look for bright flowers.”

When you add in the potential to graze livestock, the equation gets more complicated. You’ll want grass because it grows fast, but legumes provide more nutrients. In addition, consider water and nutrient availability, if you prefer to terminate the crop or if you want it to winter kill. Consider what cash crop you’re planting after it, in case diseases cross over. All in all, cover crops aren’t a simple decision.

“Build off your success and failure, but keep moving and stay committed,” Wykoff says. “Nothing in life that has great value comes easy—it’s going to be challenging. Go in expecting that so you’re not surprised by it.”

Think Through Scenarios That Might Set You Back

Inability to Manage Cover Crops
“First, choose a cover crop system that matches the management system on your farm,” says Marc Eads, Spearhead A&M agronomy consultant in northern Indiana. For example, cover crops can fail if you don’t have the ability to plant them in a timely manner.

Choking Cash Crops With Residue
“Be ready to deal with extra residue,” Eads says. If you’re not prepared to manage the foliage, your cover crops might thrive and cause your cash crop to fail. Consider looking at different residue movers or making adjustments to create a stable seedbed in the spring.

Letting Cover Crops Grow Too Long
Consider buying a sprayer because some cover crops grow fast and you might not be able to wait. “Rye could be 6" today and 12" in three days,” says Paul Jasa, University of Nebraska Extension engineer. “By the time the co-op can get there it could be 6'.”

Tying Up Nitrogen
When cover crops grow too long they can tie up nitrogen, starving young cash crop seedlings. Microbes have more work to do to break down the cover crop residue. Nitrogen might need to be injected below the surface instead of broadcast over the crop.

Starving Cover Crops
Know cover crop nutrient requirements and what nutrients are left in the soil after your cash crop. Just like cash crops, some cover crops require more nitrogen. If you don’t feed them what they need you might not establish a sound stand.

Failure to Kill Cover Crops
“We’ve had to plant into conditions I’m not 100% comfortable with because we didn’t terminate the cover in time,” says farmer Jason Wykoff. To get the cash crop in on time he’s had to make tough decisions and now works hard to make sure crops are terminated on time.

Killing Cash Crops from Shading
A lack of sunlight can kill yield in your cash crop. Look into rollers to flatten the cover crop and provide seedlings with adequate sunlight.

Loss of Soil Health Benefits
“You lose cover crops’ soil benefit when you bale up cover,” Jasa says. “We need that residue to build up the soil.”

Following With the Wrong Crop
“Don’t follow cereal rye with corn,” Eads says. “Rye needs to be terminated way in advance of corn because of allopathic effects in the soil. Also remember, sunflowers can carry white mold to soybeans.”

Picking Weed Infested Seed
Avoid bringing weeds onto your farm by working with well-known seed suppliers. 

Three Ways Cover Crops Promote Soil Health

Cover crops not only help with issues such as wind and water erosion but they help build stronger soils, too.

“When we want to make healthier soil I think about three factors,” says Paul Jasa, University of Nebraska Extension engineer. “Water, carbon dioxide and sunlight energy.”

Consider rainfall accumulation and the soil’s water-holding capacity before selecting a cover crop. Depending on your needs, cover crops can either help dry out wet soil or cover the ground to slow water evaporation in dry soils. Learn each cover crop’s water needs and how quickly they provide ground cover and to what thickness.

“If we don’t use cover crops, we’re wasting opportunity to build carbon dioxide in the soil,” Jasa says. Because you can’t store carbon dioxide the next best strategy is storing it in the form of carbon biomass in the soil—that’s what will help build organic matter.

Sunlight energy can help feed soil microbes but a crop needs to be present. Crop production uses the soil for five months out of the year—cover crops build microbial activity in the other seven months.


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Spell Check

Caledonia, MN
3/10/2017 08:35 PM

  It says 7 months, cover crops build microbial activity, what about if the soil is froze hard for 4 months out of those 7, up in North Country??? & my Dairy neighbor is going to plant corn again?????? Following With the Wrong Crop “Don’t follow cereal rye with corn,” Eads says. “Rye needs to be terminated way in advance of corn because of allopathic effects in the soil. What's way in advance mean?, in days or months??

Pine Island, MN
3/11/2017 08:34 AM

  If we look at the work done around the country by university researchers (ISU) the allopathy affect on corn after rye is more of a Nitrogen management issue than a toxin affect. The carbon to nitrogen ratio is compromised therefor the "N" is tied up in the residue. we have found adding 50 # N in the row at plant negates any issue with lack of N , N tie up or allopathy affect. Broadcast or injected N fails to be concentrated enough in early corn growth to provide adequate N before sidedress so yellowing occurs.


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