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Corn+Soybean Digest

Same Field, Same Season

When producers in north-central Ohio talk about MRI, one thing is certain — they're not referring to the elaborate, million-dollar equipment found in hospitals.

In this case, MRI stands for Modified Relay Intercropping — an alternative cropping system that involves accurately interseeding soybeans into wheat so that two crops are growing in the same field during a crop season.

Steven Prochaska, an Ohio State University (OSU) ag extension educator in Crawford County, has researched this system for nearly 15 years.

“Relay cropping has been around a long time,” he says. “However, MRI is different since it involves planting soybeans (non-polymer coated) into wider wheat rows. MRI soybean planting normally occurs from around June 1-20 — with the goal of having a well-established soybean plant (V2 to V4 growth stage) at wheat harvest.”

More specifically, MRI involves planting wheat in slightly wider row spacings, 10-15 in. apart. Traditional wheat row spacings are 7-8 in. wide. Soybeans are then planted into the field three or four weeks prior to wheat harvest in row spacings that match the wheat.

A tramline (visible wheel tracks that can be followed year after year) is essential to guide planting soybeans into wheat and to minimize wheat injury from equipment. When harvested, wheat is cut just above the top of soybean plants and the straw thoroughly chopped and spread behind the combine.

“The MRI system may better utilize sunlight energy and soil moisture in the production of two crops in one year from the same field,” says Prochaska. “This, plus the differences in crop growth requirements and grain, helps producers effectively hedge production and price risks in most years. It can also help reduce fixed costs associated with production of the concomitant soybean crop. MRI even has the potential to increase profitability and protect the environment, if done right.”

MRI has caught the attention of producers in several counties in Ohio, Prochaska says, and is now used on about one-sixth of Crawford County's 20,000 wheat acres.

Be sure to walk before you run if you're interested in trying MRI. That advice comes from Dave Brewer, a cash grain producer in Crawford County.

Brewer farms about 850 acres with his father, raising 150 acres of wheat, more than 300 acres of soybeans and the balance in corn. He has about 125 acres under MRI.

“Soon after the Hessian fly-free date of about Sept. 26 I use my 18-row Great Plains planter to drill wheat on 10-in. rows,” Brewer says. “I also use a 20-in. tramline to accommodate the width of the tires and equipment for planting soybeans.

“Typically, we like to plant the beans about 30-40 days prior to wheat harvest,” he says. “Of course, so much depends on the weather. This year we planted our beans around June 6 and harvested wheat the first week of July.”

The timing of planting with MRI is important. “You don't want beans to grow too tall and then risk losing them during wheat harvest, nor do you want beans becoming too spindly as a result of shading from wheat if you plant too early,” he says. “You're definitely facing a balancing act in this situation.”

Prochaska adds, “Light, or the lack of it, has a profound effect on the growth of intercropped soybeans.”

This is one reason Brewer scopes out state wheat variety trials, checking on standability, shorter height and more of an upright leaf posture that doesn't get too bushy.

“The past 10 years I've been averaging around 68 bu./acre of wheat and about 20 bu./acre of soybeans,” he says. “To help fill out those beans, the timing and amount of rain — especially during July and August — becomes extremely important in successfully working with MRI.”

Brewer applies 2, 4-D for broadleaf weed control on wheat in the spring. Additional weed control is determined after wheat harvest. For fertilizer, he topdresses a dry 9-23-30 before wheat is planted in fall. This is followed with a liquid topdress of 80 lbs./acre of 28% N in spring.

During past trials, research has shown that soybeans in the MRI system have yielded about 50-60% of Crawford County's average (28 bu./acre), Prochaska says. MRI wheat yields are expected to hit 85-90% of conventional wheat yields.

Despite the overall success of MRI, Prochaska underscores that significant management is required to make the system work.

“Selecting seed varieties and calibrating equipment needs to start in the off season — or at least a year in advance — before trying your hand at MRI,” Prochaska advises, adding that the timing of interseeding soybeans is critical.

Also, tramlines need to be established before planting wheat. If they aren't, then producers will find it very difficult to drive through wheat without seriously damaging it, Prochaska adds.

However, since wheat fills in gaps so well by tillering, producers can be somewhat flexible in how to set up row spacings, he says.

Some producers have taken MRI a step further by using specially built rims fitted with narrow tires, such as 14, 15 or 16 in., on their large, 200-hp tractors. Then, they may use tramlines measuring less than 20-in. wide to accommodate the wheel width. Row spacings are then set accordingly.

Tramlines help control or confine wheel traffic to specific paths and widths, leaving much of the soil untouched. So, using tramlines — combined with 100% plant cover — mitigates soil compaction, reduces soil erosion and improves overall soil quality, and potentially increases crop performance.

“Soybeans need about 8 in. of rain from June through August, combined with residual soil moisture during this time period,” says Prochaska. “Since wheat tends to use up the soil moisture reserved for soybeans early in the season, a year with inadequate rainfall or a drought will substantially hurt the soybean crop.

“MRI is a good system that works,” says Prochaska. “Our goal with alternative cropping systems like MRI has been to help producers make money and to help them protect the environment.”

Advantages Of Intercropping

  • Lower fixed costs for land and machinery with production of a second crop in the same field.

  • Better utilization of farm management labor, time and equipment.

  • Lower cost of production for MRI soybeans (a result of a lower weed control costs).

  • Hedge production and price risk by growing and marketing two crops — wheat and soybeans — in one growing season.

  • Advantages for conservation compliance planning.

Disadvantages Of Intercropping

  • Not adapted to droughty, poorly drained or very heavy clay soils.

  • Potential increase in soybean pests such as soybean cyst nematode.

  • Success of soybean crop is dependent on timely and adequate July and August rainfall.

  • Wheat susceptibility to Fusarium head scab (not worse in wheat to be interplanted). In the event of severe infection, may greatly reduce the potential profitability of the system.

  • Requires timely field operations.

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