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A 3-Step Approach to Interseeding Cover Crops

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As growers continue to search for opportunities to create healthier soils and increase yields, more trusted advisors and farmers are looking to interseeding cover crops. The practice has proven itself as an effective way to enrich soils with various nutrients, preserve moisture, and fight the effects of water and wind erosion, all leading to improved soil health and increased sustainability.

The concept of interseeding isn’t new, and a form of interseeding, known as intercropping, is quite common in some regions of the world, such as Africa. In these areas, farmers plant multiple crops in the same field, which helps minimize risk and protect producers from total crop failure. Although this practice isn’t as common in the U.S., there are some growers who interseed soybeans into a wheat field prior to harvest.

According to cover crop surveys conducted by Sustainable Agriculture Research and Education (SARE), cover crop usage has more than doubled throughout the last five years. It’s likely that most of these cover crops were planted after removing the previous crop, but many are beginning to see the benefits of interseeding cover in-season. This allows the cover crop to get a head start, very important in northern states where colder temperatures set in early in the fall, shortly after corn and soybean harvest.

For the most part, interseeding is typically used for cover crops that will not be harvested but instead, will be incorporated into the soil for long-term benefits. When considering whether to integrate cover crops and interseeding in a farming or consulting strategy, the following three steps may help.

Step 1 – Establish Objectives
Different cover crops can be used to achieve different results. For example, cereal rye offers a natural defense against weeds while leguminous crops add nitrogen, potentially saving on herbicide and fertilizer application time and costs, respectively.

The first step in creating a cover cropping plan is to have the grower define his or her goals for the process. This will help determine what cover crops can help meet these goals and also will determine the appropriate timing and method of application. Many university extension personnel will be able to make cover crop recommendations based on research that show which species and varieties are best suited for a region. There may also be incentives and opportunities for cost-share projects through the state or the Natural Resources Conservation Service (NRCS) that will help guide practices, seed selection, and timing.

Step 2 – Consider Climate
Each area of the country brings unique considerations for crop choice as well as timing. In either extreme, whether the warmer climates of the South or colder climates of the North, cover crops must be selected and timed appropriately.  For example, some cover crops can become weeds or require chemical control if they are prone to overwintering, while others are simple to control and will die at the first frost.

When objectives have been outlined and timing taken into consideration, the grower may now choose the method of interseeding, which can be simplified into three main methods.  

Step 3 – Choose a Method
Although interseeding is becoming more common, it is not without challenges. The method that is chosen will vary for each grower according to the equipment and services available.

Option 1 – By Air

A small airplane can be used to broadcast seed into an existing crop. Many aerial applicators are set up to spread dry products, including cover crop seed. While an aerial application may be slightly more expensive than ground-based services, the advantage is that interseeding via airplane can be done at any stage in the growing process – regardless of how tall the current crop is.

Potential disadvantages include not having enough moisture in the soil or forecast to ensure successful germination and establishment since the seeds are not incorporated. There is also no guarantee that all the seeds will even reach the soil, as some may get tied up in the canopy of the currently growing crop. For this reason, many will apply a higher rate of seed to compensate, further increasing application costs.

Option 2 – By Drawn Implement
A drawn implement, offered by various manufacturers, can also be used to apply seed with a standard tractor. These implements feature seed openers that create a trench between crop rows, offering direct placement into the soil, and closing wheels or chains to ensure good seed-to-soil contact

The advantage of interseeding with a drawn implement is planting effectiveness. Placing the seed directly in the soil offers the best opportunity for germination and a healthy plant stand. These implements, in combination with rate controllers and tractors equipped with GPS guidance, can deliver accurate plant populations directly between the rows, increasing the chances for a successful cover.

The biggest limitation of this option is correct timing with an existing crop. The tractor and implement don’t offer much clearance, so the process must be done in early stages of crop growth or in smaller stature crops, such as soybean or wheat. If a grower waits too long, he or she risks mechanically damaging a crop’s above- and below-ground structures, and possibly reducing yield potential.

Option 3 – By Self-Propelled Machine
With the growing popularity of interseeding cover crops, manufacturers are starting to offer equipment designed for the process. Hagie Manufacturing, in partnership with Fennig Equipment, offers a unique setup for this purpose.

Newer Hagie sprayers are equipped with a removable wet tank that can be replaced with a dry tank manufactured by Fennig Equipment. The Hagie Cover Crop Interseeder uses a high-clearance STS applicator with the dry box option and existing boom for below-canopy broadcast seeding. The Commodity Delivery System (CDS) further adds interseeding capabilities to a Hagie’s current sprayer boom with a drop tube featuring spreader fans that distribute the seed near the soil surface.

The advantage of interseeding with Hagie equipment is the clearance offered, opening the window of time the process can be performed. The Hagie equipment is able to clear taller crops and can be used later in a growing season. Another distinct advantage with this method is that cover crop seed can also be applied later in the season, limiting yield loss due to competition with an existing crop. 

Similar to aerial applications, a challenge of this option is ensuring good seed-to-soil contact since the seed is not incorporated like it would be with a drawn implement. However, a key difference is that a rate can be more accurately applied since the seed is not falling onto the crop canopy and is instead being distributed directly on the soil surface, saving in seed and application costs compared to aerial application.

The bottom line for interseeding success goes back to understanding the grower and his or her unique business – the goals they wish to achieve, the timing needed for best results, and the method that makes the most sense for their farm.

The practice of interseeding cover crops is expected to continue its growth and expansion across the country. Because it’s not a one-size-fits-all approach, growers will continue to look to agronomists and advisors to make sure it’s done successfully.

To learn more about interseeding equipment and strategies from RDO Equipment Co., contact your local store.