Post-Harvest Cover Crop Management

June 26, 2024

Cover crop management requires planning termination methods and timing, you can maximize the benefits of cover crops while ensuring optimal conditions for the following crop. Various termination methods offer different advantages depending on your specific needs and environmental conditions.

If you haven’t already implemented a cover crop, consider the benefits of adding one to your rotation. Cover crops enhance soil health, improve water management, and address issues like compaction. By understanding and effectively managing termination methods, you can unlock the full potential of cover crops, profitable, and productive farming practices.

Let’s explore the various options for post-harvest cover crops to promote resilience in your system.

Termination is integral to planning for a successful cover crop within your rotation. You want to maximize the benefits of the cover crop, while also setting up the following crop for success. When considering termination methods, it is important to determine the right method and timing to achieve your desired goals.

Natural: If you are using an annual cover crop blend, you can take a hands-off approach and let the crop naturally die through the winter months. The success of this sustainable method depends heavily on the snow cover and temperature conditions. Selecting annual species for your cover crop blend instead of perennials will also allow you to manage them this way.

Herbicide: An herbicide application completed at the right volume/stage of the cover crop is an effective method of termination. Make sure to put time into selecting the correct herbicide that will target not only the desiccation of the cover crop but also the weed species that are present.

Mechanical: To incorporate the cover crop residue back into the soil, you can complete a vertical tillage pass. This method speeds up the breakdown of plant residue, but can also require more than one pass to get control of the biomass.

If you are looking for a method with less soil disturbance, a roller-crimper implement is an effective option. This creates a protective residue layer that shields the soil through the winter months. This method has the greatest impact on soil health once the cover crop species has flowered.

Livestock: Livestock can terminate the cover crop with fall and/or early winter grazing. Not only do you benefit from terminating your cover crop stand, but the added nutrients from livestock manure while grazing help to improve the soil.

Crop scouting is one of the most important activities you can invest time in to mitigate pests and protect yields. Frequent scouting ensures timely and effective decisions are made. It also allows you to learn about the productivity of your soil. Here are some scouting tips to help you monitor the health and success of your cover crop.

Tools needed for scouting and/or biomass testing:
• Shovel
• Scissors/pocketknife
• Collection bags
• Square foot frame

What to look for when crop scouting:
Nodules: Dig up some plants in your field deep enough to expose the root system. On the roots of leguminous/N-fixing plant species, knobs form on the roots. Nodules serve the purpose of nitrogen fixation.

If a nodule is pink when sliced open, it indicates active nitrogen fixation. Conversely, if there is no color it indicates dormant or inactive nodules. Terminating a legume cover crop once the nodules are pink (N-fixation can be high approximately 30 days after establishment up to the end of flowering) will release fixed nitrogen into the soil for the next growing season.

  • Present species and weed pressure: Use a square foot frame to count cover crop species and weeds present. Successful cover crop establishment should show minimal weed presence due to competition created. These findings can help determine seeding rates for the following crop year if ground coverage needs to be adjusted.
    • You can also take this one step further and cut the plants within the frame to send them away for biomass testing. Choose the lab in advance so you have the correct protocol for gathering and sending the plant tissue sample.
  • Quantity and depth of roots: The crop sown next growing season will follow the root paths the previous cover crop left behind. If the roots have bends or curves, that could indicate a compaction layer. Note if the cover crop roots are growing though heavy layers or not. This information can help determine what types of cover crop species to grow in the future to deal with different goals such as compaction.

IF YOU DIDNT GROW A COVER CROP, consider planting one
In all climates, but certainly in milder climates, after small grains is a great time to utilize a cover crop in your cropping system. To maximize this window, it is essential to have your plan in place. This is because the best time to seed your cover crop is right after harvest, ideally before a timely rain. The earlier your cover crop is established the greater the opportunity for soil health benefits and biomass generation. Three considerations you should make to maximize benefits are selecting a cover crop seed mixture that reflects your soil needs, assessing weather impacts, and determining which crop you are planting next.

One effective way to decide what cover crop species or mixes to go with is as easy as going out in your field with a spade, digging, and examining your soil. It is important to listen to your soil. Your soils will tell you information about your operation. If you notice salts which look like white specs or have areas that are problematic water areas, you may want to work on water management within your soil profile. In this case you most likely want to look at a grass crop, small grain, or cereal rye which can over winter and continue to utilize water. If you are noticing compaction layers out in your field, you may want to focus on compaction. Perhaps in this situation you may want to seed a cover crop mix which may include a diverse group of grasses, oats, etc. While also incorporating a radish or turnip which would allow for the natural force of these plants to bust up compaction. If you notice a lack of aggregation in your soil perhaps you want to focus on building aggregation. To help build aggregation you may want to plant a cover crop mix including a variety of species including ones with deep fibrous root systems to promote a healthy environment for soil biology.

Weather is another important consideration when selecting to plant a cover crop post-harvest. In a wet year you may want to plant a diverse cover crop mix that will utilize moisture from throughout the soil profile. As well as utilizing excess moisture promoting the resilience of your farm. If the opposite is true in a dry season and moisture is at a premium. It is important to consider if you have the moisture available to establish your cover crop.

Finally, remember the crop you plan to follow the cover crop with. It is important to keep this in mind as you do not want to plant something that will cause issues down the line. A couple of items to note are potential diseases that could be detrimental to your next crop that your cover crop could be a host for. Also consider grain contamination that could occur from growing something like rye on a field intended to go into small grain production.