February Update: Diversity & Cover Crops

February 13, 2023: 
Snow cover on the fields has melted away!

By Andrea Yoder

The winter months seem to always go by quickly as we whittle away at our list of things that need to be done before spring rolls around and we return to the fields.  Winter is the time when we lay out detailed plans for crop production so that once we’re in the thick of it, we simply execute.  Ok, it’s not always that straightforward and we often need to tweak the plan to work with Mother Nature, but thinking through the majority of the details in advance gives us a good solid base for what we intend to do during the season.  It helps us source seeds and supplies, so we have what we need in advance, and helps to keep us on track with timely field prep, plantings, etc. once the busyness of the season sets in.  This month Richard and Rafael have been working on our field plan, which is the process of literally laying out the plans for where we intend to plant every crop.  We need this plan for ourselves, but we’re also required to submit this plan to MOSA with our annual application to maintain our organic certification.  This is a big task and there are many factors that go into the decision making when deciding what to plant in each location as well as when.  In fact, Richard and Rafael started to lay the foundation for these  decisions late last summer and into the fall as we were planting our end of season cover crops, the topic for today’s discussion!    

February 13, 2023:   
Winter kill cover crop in foreground

If you’ve been with our farm for the past few years or more, you likely know that cover crops are something we invest in very heavily and they contribute greatly to the health of our fields and crops.  I have always been intrigued by human nutrition, but human nutrition is directly related to plant nutrition so by default I am also very intrigued by what it takes to grow healthy plants that are packed with nutrients!  Cover crops are plants that we seed in between vegetable crops.  We’ve known for many years that they help to prevent soil erosion and contribute greatly to soil fertility.  Earlier this week the snow cover on many of our fields melted away.  As I drove through our valley I could see various shades of brown and green plant covers on our fields.  This sight, in addition to recent crop planning conversations I overheard between Richard and Rafael, got me thinking more about cover crops.  You see, when I first came to Harmony Valley Farm, there were just a few basic cover crop mixes.  You had your blend of oats and peas, a winter kill mix.  This means it likely won’t survive our Wisconsin winters   and all of the growing benefits will be realized in the fall.  We also had a mix of rye and vetch which is a cold hardy blend that will survive the winter and continue to grow in the spring.  Each blend contained a grass and either a legume or a pea.  Legumes and peas help to take nitrogen from the air and store it in nodules on the root of the plant. If you are planting cover crops in the fall and know that you need to plant an early season vegetable crop in a field, you would choose to plant the oats and peas that will winter kill.  If you know you will be planting a mid to late season vegetable crop in a field the following year, you may choose to plant the cold hardy mix that will survive the winter and continue to grow in the spring. But as I thought about our cover crop regimen in recent years, I’ve noticed that Richard keeps adding different seeds and the cover crop blends have become much more complex and diverse!  “Richard, What’s Up?!”  

Nitrogen nodules on the roots of Austrian
Winter peas

I thought you may find this little bit of Richard farming history to be of interest. I asked Richard to remind me of when he started using cover crops in his farming practices to which he answered (with a little smile) “Well, it dates back to the early 70’s.”   That was his way of telling me that he’s always used cover crops, even before it was a thing on organic farms!  His inspiration came from Rudolf Steiner, an early contributor to the philosophies of biodynamic farming.  As a beginning farmer, Richard studied Steiner’s philosophy.  One of his unique perspectives was the idea of “Solar Capture.”  We know plants need sunshine to survive and thrive, but what they are really doing is capturing the solar energy and converting it to carbon which can be stored.  Steiner’s philosophy was that, as farmers, to maximize solar capture was the equivalent to putting money in the bank!  Every day of sunshine affords you the opportunity to capture sunlight, but in order to do this you need a plant.  Richard took that concept and applied it to a Midwest growing season.  Let say that we have on average about 240 days out of the year when there is the potential for sun to shine down on a plant that is not covered in snow.  Our longest season vegetable crops are about 120 days from planting to maturity.   That’s only 50% of what is available to us, which is where cover crops come into play.  If we plant a cover crop in that soil, we can stay in the game and continue to bank solar energy.  This concept is what supports the urgency in late summer and early fall to prioritize seeding cover crops as soon as possible after we finish a vegetable crop.  Every day you wait is one day lost!

Field of Crimson Clover

Thankfully, in recent years more farmers and players in agriculture have joined us on the cover crop bandwagon.  With this growing interest, we’ve also seen some very interesting research demonstrating that the interplay between beneficial microbial communities in the soil and cover crop plants is far more complex than we fully understand!  Each plant interacts with and supports different soil microbes, so by adding diversity to the plantings you also increase the diversity of microbial communities!  We are learning more and more about the benefits of these microbial communities which are essential for nutrient uptake and increasing nutrient bioavailability in the soil, amongst many other benefits!  We’ll save the detailed research and intricacies of how this works for another discussion, but know that Richard has taken these findings to heart and has been applying these principles to our ever evolving cover cropping practices.  We now have a two-sided page of potential cover crop mixes, each customized with components to meet a different need.  Each carefully crafted mix is designed to maximize solar capture, extract nitrogen from the air, form an extensive root system to hold soil in place, and add additional organic matter back to the soil in the form of the plant residue that will eventually be worked back into the soil.  This is one of the most efficient ways to put fertility on a field and, while it’s not completely “free,” it is a great way to extract resources from the air and atmosphere and deposit them exactly where you want and need them!  

Our mixes now contain a diverse blend of grasses along with different nitrogen-fixing plants which may include not only vetch and peas but also lentils and a variety of clovers.  Richard has created different blends for different points in the season.  If we’re planting cover crops in August or September in a field that we know we will want to plant a vegetable crop in early the following year, we’ll plant a mix that will winter kill, but includes things that will be able to get closer to maturity in the 2-4 months or so that we have before we see a hard frost.  If we’re planting cover crops in that same time frame of August to September, but we know we will not need to plant a vegetable crop in that field early in the spring, we’ll take advantage of those additional solar capture days and plant a mix that will include cold hardy plants that will survive the winter and resume growth in the spring.  The grass portion of this mix typically includes different rye varieties that will maximize the growth of in the spring.  Just before they form a seed head we’ll cut the crop and bale it so we can use it to mulch vegetable fields.  In this case we add yet another benefit of having the cover crop! 

Early November Cover Crop Seeding

Our most diverse mixes now may include up to 6-8 different plants!  We’re still planting oats and peas, but now this mix also includes Japanese millet, Crimson clover, Frosty Berseem clover, balansa clover, lentils and sorghum sudangrass.  We continue to plant cover crops until about the first of November, but we use plants that establish a root system more quickly and seed it twice as thick since we’re running out of time and the nights are getting cooler which slows the growth rate.  We know that there are huge benefits and gains to having even a small plant in the soil, so we do what we can to get something growing!  It can be quite a task to manage this level of diversity and customization, but when we pull it off it’s quite remarkable!  This winter we are researching specialized equipment to seed and cover seed under and between rows of an actively growing vegetable crop.  As soon as the crop is harvested, the cover crop seed is already established and will immediately take over capturing the sun.

I have to say, I’m quite proud of Richard, Rafael, Silvestre, Angel and the other crew members who contributed in a variety of ways to ensuring our fields were “put to bed” for the winter with a blanket of some type of cover crop or plant matter.  All vegetables are not created equally and it is the details such as these that move the needle from “good” to “superior!”  We strive to grow superior vegetables in every aspect, from appearance to flavor to nutrient value.  We see the benefits in the fields, but hopefully you are seeing and tasting the benefits as well!