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| Hi Tom,
we did an experiment in 2007/2008 that included radish no-till drilled into red clover, radish and oats no-till drilled into red clover, oats no-till drilled into red clover and radish drilled into tilled out red clover. The red clover had been frost seeded into wheat and was allowed to grow for ~ 4 weeks after wheat harvest before some strips of clover were tilled out and the cover crops were drilled.
Corn yields the following year were 10+ bu higher in all of the radish treatments as compared to the clover-oat treatment. To our surprise, all of the radish treatments had comparable corn yields... even though the radishes in the tilled out strips grew more than twice as much biomass as the no-tilled radishes. Seems that the additional red clover growth where the radishes were no-tilled may have helped to balance out the effects of the much larger radishes where the clover was terminated early by tillage. We did not apply any supplemental N.
My guess is that you will see a significant N release and growth response by the radishes if you terminate the redclover with glyphosate or 2-4D before planting radish (even if you don't quite kill all of the red clover)... more radish growth did not result in more corn yield for us but I suspect that it would have if N had been less limiting.
Joel
WIU Agriculture
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Cover crop twist after W. Wheat
