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OSU Extension

College of Food, Agricultural, and Environmental Sciences

March 21, 2016 - 8:38am -- Anonymous

Cover crops provide multiple benefits with regards to protecting soil from erosion, improving soil health, and as a component of a nutrient management plan.  For those cover crops that over winter and resume growth in the spring, for example, cereal rye and annual ryegrass, an important question is when to terminate that cover crop.  That decision should consider the next crop, planting date of that next crop, the spring weather pattern and purpose of the cover crop.   For cover crops that have not been planted with the intention of providing a forage harvest, and that are on acres intended for corn grain production, this may be a year to consider early termination of that cover crop.

A driving factor for early termination of cover crops this year is the potential for a drier than average spring and summer.  On a recent OSU Extension Ag Crops team conference call, Jim Noel from the National Weather Service talked about weather patterns following an El Nino year.  Often the pattern is for the spring and summer months to be drier and warmer than average.  At this point, warmer than average weather and plant growth points to an earlier spring. I have talked with several farmers who tell me that our soil moisture is drier than average.  If this pattern holds, the risk is a cover crop can take up moisture that should be saved for the cash crop.  At the recent conservation tillage conference in Ada I saw data that showed lower corn yields following cover crops in dry years when those cover crops were not terminated early enough.  Those cover crops robbed soil moisture leading to delayed germination and slower development that was not made up compared to a corn crop planted with no cover crops or planted into a winter killed cover crop. 

Given the risk of or the potential for a drier than average spring and summer, cash grain corn producers should consider terminating cereal grain and annual ryegrass cover crops in the late March to early April time frame.  Ideally we would like to see less than 8 inches of growth for either of those crops and I have read several sources that say annual ryegrass should be terminated before 6 inches of growth.  The recommended method for early termination is the use of herbicides.  Glyphosate should be effective, especially if day time temperatures are above 50 F, and is probably one of the most economical options.   A Purdue Extension publication entitled “Successful Annual Ryegrass Termination with Herbicides” says that producers need to use at least 1.25 lbs. of acid equivalent /acre of glyphosate and possibly up to 2.5 lbs. of acid equivalent /acre of glyphosate under less than ideal conditions for herbicide translocation.  Mark Loux, OSU Extension weed specialist recommends a minimum rate of 1.5 lbs./acre of acid equivalent glyphosate.

Another common cover crop situation in our area is the use of cereal rye with the intention of taking a spring forage harvest and then planting corn into the stubble.  I have had some questions about cereal rye and potential allelopathy reducing corn yields.  This topic was addressed at the Conservation Tillage Conference by OSU Extension educator Jim Hoorman who has specialized in cover crops and cover crop research for many years.  Jim said that the allelopathy attributed to cereal rye comes from toxins in the leaves and stems of the plant.  Therefore, it is important to remove the growth as forage before planting corn or terminate the cereal rye at an early vegetative stage.  If the cereal rye gets away and goes into reproductive growth or gets too mature to harvest as good quality forage, this growth should still be removed from the field before corn is planted rather trying to chemically kill it and/or tilling it under.

For more information about cover crops and spring termination options contact the Wayne County Extension office at 330-264-8722.