Cover Crop Considerations in Northern Latitudes

• Cover crops have increased in popularity in recent years and offer potential benefits such as:
  • Reduced erosion
  • Improving soil structure
  • Improving biological activity of the soil
  • Sequestering nutrients
  • Suppressing weeds
• While there are many benefits to incorporating cover crops into farming operations, there can also be challenges.
• Getting a cover crop established and then terminated in northern latitudes can be challenging due to shorter growing seasons and colder spring temperatures.

1. Cost of Cover Crop System

• Seeding cover crops is an added expense and it is important to consider species of cover crop to be seeded, herbicides utilized, timing of seeding, equipment used to seed and weather conditions following seeding -- along with terminating cover crops in the spring.

2. Establishment Timing

• The growing season in northern latitudes is shorter and to get the most out of a cover crop, it often needs to be seeded prior to harvest of the cash crop. Cover crops require 6 weeks of growth before a hard freeze to be most beneficial.

3. Establishment Method

• Seeding equipment continues to evolve but one of the predominant methods of seeding cover crops has been with aerial application. This requires the use of a cover crop species that does not need good seed to soil contact to grow.
• Aerial seeding or broadcast seeding in late August can be an effective way to establish a cover crop. In dry summers and falls this may not work.
• Ideally cover crops would be seeded with a drill after harvest of the cash crop. The length of fall growing season often prevents this from occurring in northern latitudes.

4. Cover Crop Species

• Consider using cover crops such as oats that winter kill if the subsequent cash crop is corn to prevent stand establishment issues in corn.
• Cover crops such as cereal rye will overwinter through most winters and will provide cover in the spring. This may create challenging planting conditions for corn, but it may be a good choice for use ahead of soybeans.

5. Cover Crop Termination

• One challenge with terminating cereal rye can be low air temperatures which can be common during spring in northern latitudes. Try to time herbicide applications when nighttime temperatures are above 40 °F (4 °C) and daytime highs reach 60° F (16 °C).
• Planting corn after cereal rye can be done but it is usually best to gain experience with a species that winter kills first then begin to incorporate winter hardy species.
• There is some evidence that cereal rye can have an allelopathic effect on corn if termination is too close to corn planting.
• Planting soybeans after cereal rye can be done when the rye is still green or after it has been terminated.

6. Herbicide Selection

• Pre-emergence herbicides may reduce stand establishment or reduce grazing opportunities of cover crops. Always read and follow herbicide label guidelines.

• Start with a simple program to gain experience.
• Understanding how to terminate cereal rye ahead of soybeans will lead to better management of winter hardy cover crops ahead of corn.
• Other species such as brassicas and legumes can begin to be added to the cover crop mix as experience is gained.

• DeJong-Hughes, J. 2021. Guide to Planting Cover Crops in Minnesota. University of Minnesota Extension.
• Hartzler, R. 2014. Terminating Cover Crops. Iowa State University Extension. Integrated Crop Management.
• Wick, A., C. Gasch, and M. Berti. 2018. Incorporating Cover Crops. North Dakota State University. SF1901.