As a Cover Crop, How Does Wheat Compare to Cereal Rye?
Dr. Erin Haramoto — UK Weed Science Assistant Professor\
We’ve conducted an experiment over the last two years to compare how wheat and cereal rye perform as cover crops—research funded by the Kentucky Soybean Promotion Board. We drilled and broadcast two different seeding rates (30 and 100 lbs seed/acre) of each species and measured establishment, ground cover, and biomass of both the cover crop and winter weeds. All cover crops were planted in mid-October after corn harvest in Lexington; we drilled using a commercial-scale John Deere no-till drill and mimicked broadcasting the seed prior to harvest (so seed was on the soil surface rather than on the corn stover).
The species, planting method, and seeding rate can all influence the amount of cover crop biomass produced. Cereal rye produced more biomass than wheat in almost all conditions, but particularly over the winter of 2016-17. Other researchers across the Midwest, the Midsouth, and South have noted this too—cereal rye suffers less mortality from cold temperatures than wheat and also has a lower base growing temperatures so can put on more bio-mass during our mild winters when temperatures are marginal for wheat growth. Drilling seed was essential in the Fall of 2016 when it was very dry—the North Farm received only 2” of rain in October and November and broadcast seed did not establish well at all this fall! This poor establishment led to low biomass production the following spring—plots with broadcast seed produced only about 25% of the biomass compared to those with drilled seed. Interestingly, reducing the cereal rye seeding rate actually increased biomass production in one year! It had the opposite effect for wheat. Where we had more cover crop biomass, we generally had less winter weed biomass (weeds like common chickweed, purple deadnettle, henbit, etc.).
What about ground cover over the fall, winter, and early spring? We measured this by taking digital photos and analyzing the amount of green (plants) as opposed to brown (soil). Usually, cover crops that produced more biomass also produced more ground cover. So, drilling seed in that dry fall resulted in better ground cover, and planting cereal rye instead of wheat resulted in more ground cover. When we had a cold snap in early 2018, cereal rye lost less ground cover than wheat and rebounded quicker (again, since it is more tolerant of these cold temperatures). But, increasing the seeding rate also increased the ground cover produced, though it didn’t affect biomass production in the way we expected.
So… is cereal rye a better cover crop than wheat? It depends what you want to get out of the cover crop. If you’re concerned with having too much biomass in the spring, then wheat may be a good option. You can’t just decrease the cereal rye seeding rate and expect to get less biomass! However, be aware that you will likely get less ground cover and more winter weeds with the wheat than if you used cereal rye. We did this trial with ‘Aroostook’ cereal rye and ‘Pembroke 2014’ wheat—and the results may vary with different varieties!
Our research into cover crops continues—we currently have projects in both corn and soybean looking at different cover crop planting dates, cereal rye varieties, combining cover crops and herbicides for best weed control, and many others. We’ve also just wrapped up a large project on mixtures of crimson clover with both cereal rye and wheat and are analyzing data on how planting date and termination date affect nitrogen contribution, for-age quality, and also weed control. Stay tuned for these results!