Modified Relay Intercropping (MRI) is the planting of soybeans into standing wheat versus double cropping soybeans that are planted after wheat is harvested. Vyn et al found that relay intercropping of soybeans yielded better than double cropping of soybeans north of I-70 in Indiana. 2014 Ohio research showed a 10 to 25 bushel advantage to MRI over double cropping at OARDC Western and Bucyrus, Ohio respectively. Budgets also show MRI to have $150 gross advantage over other grain operations or a $50 advantage over monocrop soybeans.
Prochaska et al showed that in the past 16 years of replicated trials in North Central Ohio, MRI wheat has averaged 74 bushels per acre and soybeans 31 bushels per acre. Wheat that was planted close to the fly free date in favorable growing conditions has exceeded 90 bu/acre and soybean field averages have been over 54 bu/acre.
Successfully seeding MRI soybeans into a growing wheat crop requires planning at wheat planting time to minimize wheel traffic damage. Usually tram lines are utilized in 10 inch wheat rows to allow for the tractor and planter to drive in the wheat field without damage. Wheat row spacing’s in MRI have varied from 10 to 22 inches but wheat yields may decline with wider rows (http://corn.osu.edu/newsletters/2011/2011-27/wheat-variety-yield-in-15-i...). Even in wide row wheat, special equipment may need to be designed to fit down the 15 inch wheat rows without using tram lines.
While utilizing an existing piece of equipment on the farm is always the most economical way to start interseeding, many successful producers have built special three point interseeders to minimize the wheel trams through the field to allow all tires to follow the tractor.
The Best Management Practices for MRI soybeans include: Planning and setting up equipment for interseeding in the fall before wheat is planted. If the wheat is sown and you are building an interseeding tool bar, taking the equipment out first thing in the spring before wheat Feekes 5 and testing wheel and unit alignment to save time during planting. If any of your wheels or units happen to fall on a wheat row at this time, you won’t damage the wheat. Seeding generally occurs between Feekes 10.1 and 10.5, generally between June 1st and the 20th. Some producers have had success interseeding when wheat is in the boot stage in wide row wheat that has enough sunlight reaching the ground that the soybeans are not stretching to find the sun. Current seeding rate recommendations are between 200,000 and 250,000 / acre, depending on soil moisture, timing and the ability of your planter to penetrate the ground and close the seed trench.
For more information on different MRI practices, visit: https://agcrops.osu.edu/on-farm-research