Updated July 4, 2018:

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Effective Winter Rye Management for Maximum Soybean Potential – Executive Summary
Mike Ostlie, Greg Endres, and Steve Zwinger

2017 marked the end of a research phase with the rye and soybean relay cropping system. The goals of this system include preventing erosion, managing glyphosate-resistant weeds, grazing/haying, or creating a more firm spring seed bed. This research was initiated in 2013 with the goal of identifying effective rye termination methods so that soybean yields were maximized. Rye and soybean planting dates were added as components over the last three years.

Our rye planting dates ranged from Aug-Nov each year. Spring survival remained high through early October planting. The early November planting still had 60% spring survival, even though it did not emerge after planting in the fall. For some uses of rye this opens the possibility of planting rye after corn harvest, though winter cover and biomass production would be considerably lower than earlier planting. Mid-season planting into corn, or planting after an earlier harvested crop would increase the benefit of rye.
The timing of rye termination is biggest key to success with the rye and soybean relay. In our previous work with rye termination, we found glyphosate to be the most consistent method for termination. Since 2013 when rye was terminated 2 weeks prior to planting there was no impact on soybean yields. Terminating the rye at soybean planting often had a similar yield to the check, but waiting until 2 weeks after planting often led to lower yields. There was 1 complete crop failure when terminating at soybean planting and 3 crop failures when waiting until after planting.

Available soil moisture is what determines the success of soybean establishment. One of the assumptions of our research was that planting soybeans into rye earlier would be safer since the rye would be smaller and using less resources. However, in 2016 and 2017 we had two very dry springs where some of the lowest soil moisture levels for the year were in May. In both years, when we planted soybeans in early May into rye there were lower yields compared to the check. Whereas in both years, we had early June rains and there was no impact of rye on the soybeans, indicating it was more risky to plant soybeans early those years. However, it should be noted that even though the early planted soybean were affected by rye, the yields were still equal to the best treatments at later soybean planting dates.