Frost seeding a cover crop in March

February 15, 2011 

With 75-90 days of growing season remaining after wheat harvest, producers typically need at least one herbicide treatment or tillage pass to keep weeds and volunteer wheat under control.  Why not use that time to grow nitrogen instead of weeds by planting a red clover cover crop? 

In addition to providing nitrogen, a clover cover crop can help control weed growth, build organic matter, reduce soil loss, and scavenge excess nutrients that might otherwise be lost as runoff. 

Red clover is “frost seeded” into dormant winter wheat in mid to late March after snowmelt, when low nighttime temperatures cause the soil to freeze and crack.  Warmer day time temperatures create thawing at the soil surface, and close the cracks.  The best time of day to broadcast the seed is early in the morning when the cracks are frozen open and the stiff soils support the application equipment. 

The seeding rate is 10 lbs/acre of red clover seeded with a broadcast seeder mounted on the back of a utility vehicle, tractor or pick-up truck.  Double spreading at a half rate helps illuminate skips. 

Red clover seedlings under wheat canopy in early July

For larger acreage, spreading clover in conjunction with a spring urea application using an air flow system has provided good results.  Spreading clover in conjunction with a urea application using the traditional “pull behind spreaders” has not produced good results as the red clover is lighter then the urea, and the spread pattern is much smaller, leaving strips throughout the field where clover is not established.      

The red clover seedlings are established early in the spring and remain small under the wheat canopy and do not interfere with wheat harvest. 

Red clover seeded into wheat the day of wheat harvest

Once the wheat is harvested and the canopy removed, the red clover really takes off.   

Red clover seeded into winter wheat one month after harvest

The amount of “nitrogen credit” from clover is dependent on the amount of plant growth, both above ground and below ground.  

Wisconsin data suggests that 70% of total nitrogen in red clover is available the first year.   As a guideline, red clover can supply 50-80 lbs of nitrogen to the following crop.  With favorable weather and good soil moisture conditions nitrogen credits may exceed this amount.

For more details on this practice, see publication “Frost Seeding Red Clover in Winter Wheat” available at the website

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Nitrogen contribution from red clover. Image courtesy University of Wisconsin NPM Program


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