Observations from this
Season Cover crops were tried in many different situations this year. Cover crops were interseeded into corn, flown into soybeans, planted after corn silage and following winter wheat and other crops. In most situations there was plenty of moisture for germination. In some cases excess moisture slowed growth and reduced the amount of nitrogen available for the cover crop. The cooler weather reduced the amount of growth compared to the previous couple of years.
The early frost in mid-September caused injury to sensitive cover crops. A warm season legume called Sunn Hemp (included in a 6 species mix in the St Clair Region Soil and Crop Cover Crop project) was killed by that frost. It was also tried in some areas north of London with limited success. The sorghum-sudan in the mixture was also killed or set back in many of the plots.
Interseeding In Corn
Annual ryegrass, crimson and red clovers, and alfalfa established well when interseeded into corn at the 5 to 6 leaf stage. Later plantings did not establish or had poor stands. Corn herbicides can affect the success of cover crop establishment. The residual herbicides atrazine, isoxaflutole + atrazine and s-metolachlor will cause injury to annual ryegrass interseeded into corn at the 5 to 6 leaf stage.
Fall Management
There are many options for managing cover crops this fall. The best option will depend on the type of cover crop, tillage system and crop to be planted next year. One of the main purposes of cover crops is to keep the soil covered so the cover crop should ideally be left as long as possible, preferably until the spring.
Many cover crops will be killed by the cold. Radish, oats, corn, soybeans, sorghum-sudan, peas and others are sensitive to a killing frost. It will take a temperature of minus 5°C to kill radish. Other cover crops such as the winter cereals, annual ryegrass and the clovers will survive the winter. If there is concern about killing these crops in the spring, then control them as late as possible in the fall. Strip tillage is an option for preparing a seedbed for the following crop. This would usually be done in the fall. If tillage is used in the fall, try to keep it to a minimum because:
- you want to leave enough residue to protect the soil over winter, and
- excessive tillage will wipe out any soil benefits.
Many farmers have successfully no-tilled corn into undisturbed cover crop residue.
The Red Clover Advantage
If cover crops are being considered for 2015 and winter wheat is in the ground, don't forget about red clover. It is still the cover crop of choice and has these advantages:
- low cost,
- planted when there are few demands on time,
- easy to seed,
- can be covered by crop insurance,
- provides a 80kg/ha nitrogen credit to the following corn crop, and
- produces more root and shoot biomass than most cover crops planted after wheat harvest.
Patches that don't establish can be filled in with crimson clover. If the red clover stand is poor overall, there is still the opportunity to plant a cover crop after the wheat is taken off.
While the opportunity to plant a cover crop may not come as early as desired - the key is to get them planted. Research from Dr. Laura Van Eerd, University of Guelph, Ridgetown Campus suggests that the root growth and overall presence of a cover crop is the critical thing.
The key cover crop message is to plant early and plant often!
Source: OMAFRA