Getting Started with Cover Crops
By Tanya Allemang, District Conservationist
Natural Resources Conservation Service
You have read all the articles on soil health and you know how important it is. You have decided you want to try and plant cover crops, but where do you go to get started? The best thing to have is a mentor or friend that you can bounce off ideas. Look around, there may be other like-minded people in your area that may be already experimenting with cover crops. They would be an excellent source of information and experiences. If you don’t have anyone near you, you might be able to access the web and find others with whom to share experiences. Talk to your local Natural Resources Conservation Service (NRCS) office and conservation district, they may be aware of additional resources available to you.
You are determined to do this on your own, so what do you need to know? You first need to understand the four principles of building soil health.
Minimize disturbance of the soil; disturbing the soil destroys the home of the microbiology and the soil aggregates that you are trying to build.
Armor the soil. The soil needs to be covered as much as possible to protect it. The biology’s home won’t be very effective if you don’t give it a roof.
Supply living roots for 10 months per year on average. The biology needs a constant diet for optimal health. A feast after harvest and a famine during fallow will not build a population very quickly.
Maximize crop diversity. Biodiversity is good. Biology needs to eat from the 4 food groups: warm-season grass, warm-season broadleaf, cool-season grass, and cool-season broadleaf. Make some of those broadleaves a legume for good measure.
Start with a small piece of ground that you can devote the management time to. If this is new to you, you can make mistakes, that is how you learn. I’ll bet you didn’t learn to walk without falling down a time or two. Leave a check or control strip in the field. That’s how you can tell what you are learning. Keep that strip in the same place every year. Over a few years of cover crops versus the control strip you will be able to see where you are going. In addition, it will make a great field tour.
When should cover crops be planted? Any open field is an opportunity to plant cover crops. You will see the benefit as long as there is one month of possible growth before weather or the next crop requires termination.
What should I plant? That is a more complicated question that would need a longer article. In short, you want a multispecies mix with a minimum of at least five species with preference given to mixes with seven or more species. The reason is the different plants all have different levels and angles of leaves to maximize available sunlight and they have different root structures to maximize root growth. In addition there is a synergy between the plants that we don’t yet understand, but they are collaborative and benefit from each other. You also want to have a clear objective in mind for the cover: when do you want to plant it, terminate it, termination method, and what crop will follow it. With answers to those questions the seed dealer can better assist you in developing a mix.
What is a carbon to nitrogen (C:N) ratio and why is it important? Again that would take a longer article to get detailed, but in short the higher C plants are slower to decompose (such as cereal grain straw). Plants lower in C have a lower C:N ratio and therefore decompose rapidly (such as legume residue). When you are new in your system, the lower C:N ratio plants are good and can jump start the biology. Carbon is what drives the system. You need to have a high enough C:N ratio that you are leaving a good residue mat. As you progress in this system you will need more and more high carbon plants in order to have adequate residue coverage. You never want to have your residue decompose so quickly that it leaves bare soil.
What kind of drill do I need? Most people just use the wheat drill they already own. The mixes stay pretty well mixed in the box provided you don’t drive a couple hundred miles over gravel roads before drilling. This may cause settling out of seed. Even if the field isn’t exactly drilled uniformly it is not critical. Some plants may grow better in one area of the field than another. Use the seeding depth for the deepest seeded plant in the mix. The shallower seeding depth plants will be able to follow the root channel made by the deeper seeded plants.
When should I terminate it? Please refer to the Natural Resources Conservation Service (NRCS) Cover Crop Termination Guideline available at your local NRCS office, or by contacting your local Risk Management Agency office.
During dry years, some people have experienced slightly poorer yields following cover crops the first year, particularly when it is in a young no-till field (less than 10 years of established no-till). Similar to no-till, it takes a while for the system to build and the benefits to be realized. You have to realize this is a biological system and is affected by the environment. All exponential growth curves initially start slow and build from there. Anytime the moisture or temperature is not optimum, the growth of the biology is slowed or halted and will resume when the conditions are right. So improvements and growth will take longer in drought years and will take Western Kansas longer than Eastern Kansas due to precipitation. You just need to stick with it and be patient. The system will build upon itself.
Make planting and managing cover crops a priority. You can’t expect first class results, if planting the cover is a second class priority, something you might do when everything else is done. Believe in it, because if you don’t think it will work then you’ll prove yourself correct. Give it as much opportunity for success as you can. Don’t be afraid to do something radical. Graze it or plant two cover crops in a row. Dare to be different.
Check out the NRCS soil health webpage at soils.usda.gov/sqi/. Stop by your local NRCS office or conservation district office located at your local county USDA Service Center (listed in the telephone book under United State Government or on the internet at offices.usda.gov). More information is also available on the Kansas Web Site at www.ks.nrcs.usda.gov. Follow us on Twitter @NRCS_Kansas. USDA is an equal opportunity provider and employer.