Modified Relay Intercropping (MRI) is the planting of soybeans into standing wheat and double crop soybeans 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 (http://www.agry.purdue.edu/staffbio/AY316.pdf). In 14 years of replicated trials in North Central Ohio on the MRI system, yields have averaged 76 bu/acre for wheat and 29 bu/acre for soybeans (86 bu/wheat and 0 bushel soybeans in 2012). Wheat yields in favorable growing seasons have exceeded 90 bushels per acre and while soybeans have yielded well over 45 bushels per acre.
However, too successfully MRI soybeans into wheat, wheat row spacing modification to allow soybean planting equipment to pass without running down plants should be made in the fall. Wheat Row spacing for MRI has ranged from 10 to 20 inches. As wheat row spacing widens, wheat yields may decline http://corn.osu.edu/newsletters/2011/2011-27/wheat-variety-yield-in-15-inch-rows .
There have been various row configurations used to allow soybean planting equipment. For example, some wheat producers will slide row units together to a 6 inch row spacing and leave a 14 inch planting strip for soybeans. Further many producers wish to utilize corn or soybean planter to sow wheat and this normally is a 15 inch row configuration. For 2012 data on 15 inch row wheat go to http://corn.osu.edu/newsletters/2012/2012-26/#5 . Row spacing data would suggest that wheat is an adaptable plant that will yield well over various row spacing’s up to 15 inches.
To accommodate soybean planting and allow for better wheat management via fertilizer, herbicide and/or fungicide applications, a tram line is essential. Generally, the tram line will be set up for the MRI tractor tires. Planter equipment tires are moved if necessary to follow tractor tires.
The next step is to practice MRI in the fall prior to the actual planting wheat. Take the wheat drill/planter to a field area and make rows. Next, if possible, take tractor and planter to be used to sow beans into wheat and drive as if interseeding beans into wheat to observe if tractor/planter tires will go down rows without running over them.
Finally, wheat culture for MRI, outside of row spacing modification, should remain the same as for monoculture wheat.