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One of the main challenges many farmers face with cover crops is finding the time to execute their cover crop plan. Time is scarce and valuable during the fall due to harvest, so some farmers choose to seed during the cash crop growing season. Not all seeding methods work for every farmer, and there are many options out there. Farmers who aerial seed are hoping to take advantage of a longer growing season for the cover crop and attain better growth before a killing frost in the fall.

Establishing a cover crop after harvest is one of the most common methods of seeding, but it has some challenges. In areas with late harvests or shorter growing seasons, the establishment of cover crops in the fall can be difficult. Aerial seeding applications are usually in that late summer period when there is still ample opportunity to take advantage of sunlight and heat.

Cover crops seeded in the late summer are usually applied with either an airplane or a high clearance ground rig. These each have their own set of advantages. An airplane can cover acres quickly without any crop damage, and the equipment doesn’t have to be owned or rented by the farmer. Ground rigs can be equipped with seeders and drop tubes for each row. They are very accurate but will run over some of the standing crop.

An important part of this seeding timing is developing a plan that works for your farm management system. Factors such as species selection, finding an applicator, hitting the right timing, and whether or not conditions are conducive to germination are very important. Using an agronomist can be very helpful for answering these questions and figuring out if this timing will work for you. For species selection, this could be a time to try a mix of cover crop seeds. Turnips, radishes, crimson clover, and oats can be great options for this timing and can perform better with a longer growing season. Depending on your specific soil health goals, the best options may vary.

Moisture and rainfall are factors that play a large role in the success or failure of a cover crop seeded at this time. A decent rainfall within a few days of seeding is crucial to achieve good germination from your cover crop seed. Seed sitting on top of dry soil will start to lose germination percentage after a few days. Small amounts of moisture from heavy dews or small rains can cause seed swelling which lowers germination as well.

Another consideration to think about when aerial seeding is how the canopy will affect germination and early growth. Seeding early in both corn and soybeans is troublesome due to the canopy shading out the sun. Considering plant architecture and row spacing can be helpful for understanding how sun will penetrate through your crops canopy.

Timing of application in corn is best when the leaves are beginning to dry down and roughly 50% of sunlight is hitting the ground. For soybeans, a good rule of thumb is to apply right when the leaves are beginning to yellow and drop. Hitting this timing can be difficult depending on weather and growing season conditions. Residue also plays a large part in successful germination and growth of the cover crop. Heavy residue can trap seeds and prevent their germination. It can also form a matte from harvest that could cause young seedlings to struggle to grow up and through it.

Seeding cover crops in the late summer can be a good option for many reasons. Some of these include time savings, longer cover crop growing season, the ability to use some different cover crop species, and not having to own seeding equipment. There are risks involved in seeding at this timing due to the seed lying on top of the ground and the sometimes lack of rainfall in the late summer. Trying this method out on a small number of acres could be a good idea to see how it works in your operation.

To learn more, check out the latest Soil Session webinar, titled: Aerial Seeding.

John Stewart
John Stewart
John Stewart is a Field Manager for Soil Health Partnership covering central and southern Indiana and Ohio.