After 15 years of growing 10 inch row wheat and soybeans in a Modified Relay Intercrop (MRI) system, this year wheat and soybeans were planted into two different row spacing/ cropping systems. Soybeans were intercropped into wheat (much earlier than in past years – 5/23 at one site) into a twin row system (two 8 inch wheat rows and a 22 inch skip) and a 15 inch row system.
Results of 10 inch row intercropping (average over all replicated trials) after 15 years were: 76 bushels per acre for wheat and 30 bushels per acre for soybeans. However, MRI soybean yields have not been as consistent from year to year as soybeans grown in a conventional mono crop system. With wide row wheat (15 inch) yielding relatively well in OSU Wheat Performance trials (go to:http://oardc.osu.edu/wheattrials/ ), the focus was on improving soybean yield via the aforementioned wheat row/cropping systems.
In evaluation of MRI soybeans in a twin row wheat system, a few observations follow after wheat harvest: 1. Soybeans planted into wheat (2 rows into each 22 inch skip) on May (5/23) grew well and are the R1 to R2 stages of growth with a height of up to 18 inches in some plots. 2. This year with twin row wheat harvest occurring on July 11 (waiting for wheat to dry), soybeans were clipped with up to 2 fully expanded trifoliate leaves lost which probably will not be desirable. Thus in an interseed system, we would recommend not to wait to harvest wheat until dry (ie 13.5%). Some elevators have a “wet wheat program” that may permit growers to harvest wet wheat and deliver it. 3. We would recommend interseed system wheat be planted close to the Hessian Fly Free date to promote/allow maximum wheat tillering in the fall and early wheat maturity (harvest in the summer). Follow appropriate seeding rates, fertility recommendations, weed control and seed treatments for wheat and soybeans. 4. Soybeans that are very tall and in early reproductive stages are easily killed by wheel traffic (another reason to harvest wheat at higher moisture). 4. Finally, combine wheel traffic has been very damaging to all MRI soybeans regardless of system being used (10, 15, or twin row) and will reduce soybean stands/yields.
For more information on 2013 MRI trials go to the Crop Production for Profit blog at:http://croppp.cfaes.ohio-state.edu/