**Cover Crop Seed at AJF** | Oats, radish, vetch, barley, and red clover.

Part 1 | Part 2 | Part 3 | Part 4

Management and Harvest of Cover Crops

Ah ha! And now we find ourselves back at the beginning, where this set of essays first took root when Tracy asked, “...do you till in your cover crop? If not, how do you get all that green manure into the soil? If you do till, isn’t that bad for the soil community?”

So how does one balance the importance of thriving, lush cover crops with the desire to sow vegetables in that same space?

I bet you know what I’m going to say.

It depends!

Remember, your system so far is composed of:

A primary and/or secondary goal (what you are trying to accomplish by using cover crops)
A group of carefully chosen plant species with superpowers to help you achieve your goal(s)
A specific window of time those plant species will work
A set of tools and techniques that you have readily available

When combined, all these elements of your system will naturally lead you to a winnowed list of options for what happens at the later stages of your cover crop life cycle.

Imagine a spectrum of possibilities, which depend entirely on the specific context of your system.

On one end of this spectrum is what conventional, monoculture big ag does– use herbicides to kill their cover crop, then use a no till drill to cut slices into the soil, plant seed, and cover the furrow. (This is assuming big ag producers even use cover crops, which many don’t. They just harvest the market crop and leave the field totally bare over the winter.) ACK! YIKES! NO! While I can’t stomach the thought of using poison to ‘terminate’ cover crops, I have long wished for a no till drill that was sized appropriately for our operation. Unfortunately, these drills are cost prohibitive. We’re talking more expensive than the tractor they’d hitch to. That’s too bad, because a no-till drill would be a very valuable addition to our system. In the late summer, it would allow us to direct seed fall cover crops directly into fields where we have finished harvesting market crops and it would allow us the ability to get certain plant species established in an otherwise healthy stand of cover crop, with reduced irrigation and better germination. Alas, the specifics of this dream scenario are involved and must be saved for another essay.

Ok, let’s inch away from this approach and look at another possibility that is also in the no-till camp. Instead of herbicides, organic farmers like Leah Penniman of Soul Fire Farm and Bryan O’Hara of Tobacco Road Farm have popularized approaches to cover crop management that utilize mulches and solarization. Solarization works by depriving plants of light while creating high heat conditions. This basically kills the cover crops (again, you must thoughtfully pick the right plant species for this to work). You can watch an overview of Bryan’s system here and find Leah’s excellent book here or at our public library.

I also highly recommend Bryan O’Hara’s book for an detailed discussion of the benefits of this approach and also a review of the scientific research around the effects of subjecting your soil to short periods of high heat. A cornerstone of this system is that you must be extra diligent to keep grasses and invasive perennials out of your garden beds. Spend some time perusing these resources this winter and you can’t help but come away with some great ideas and methods to try in your own garden.

Many of these types of approaches work especially well on a smaller scale where you can source enough mulching materials close to home. One approach we really love on a bigger scale is to grow our own mulch using cover crops we’ve already planted. This past year, we used a sickle bar mower to harvest a 120 ft x 80 foot block of crimson clover that was growing in one of our multi-year cover crop fields. We carried that clover right ‘next door’ to the tomatoes we’d just transplanted and used it as mulch around the base of plants. The clover regrew and continued to provide benefits to the soil while we were able to have excellent, high quality mulch for our market crops. Aside from feeling badly that we robbed the pollinators from some beautiful crimson clover blooms, boy did it feel great!

One thing to note: The short term (48 hours) use of tarps for solarization is much different than utilizing black weed barrier for prolonged periods of time. I am firmly against the use of weed barrier due to the negative effects I’ve seen at my own farm. Synthetic materials (plastics, weed barriers, tarps, etc.) basically starve the soil because no organic matter can come in contact with the earth. Leaving weed barrier out all winter causes significant deleterious effects — most noticeably major compaction. All that rain beats down on the unprotected soil with no plant leaves/structure to slow the energy down. Then this compacted soil bakes dry and you’re basically left with something akin to concrete. Sad times!

Moving on…at the far other end of the cover crop spectrum, we find another approach. That is to never take out the cover crops you’ve planted. Depending on the goals and the species, it’s possible you’ve planted perennials or quickly reseeding annuals that you don’t intend to turn under. In our fields, our goal is to have at least one 5 ft wide by 160 ft long bed every 60 feet that is permanently planted to something like alfalfa or comfrey. Such perennial plants are known soil builders but also provide beneficial services for our insect communities. And even better, alfalfa can be mowed because it regrows (if cut at the appropriate height and season). Comfrey leaves grow fast and can be an excellent, nutrient rich addition to your compost piles. Both are highly desirable food sources for poultry and ruminants. In short, these types of perennial cover crops provide a regenerative source of hay, mulch, and green fodder should we choose to use it.

One thing I want to suggest is to be aware of the beneficial cover crop species already growing in your gardens. Sometimes we think we have to annihilate everything in order to plant a crop or implement our GRAND PLAN. We think uniformity is the be-all end-all. That’s faulty thinking! Many a time we’ve had a very successful market crop that managed to peacefully coexist with some cover crop interlopers. It’s been at least 5 years since I last planted Borage, but year after year, it keeps popping up in surprising places in our fields- places where it adds value and diversity to our system. This year, you may have noticed the big patch of Milkweed and Asters in our winter squash block. Brad made a special point to till around those plants. Yes, you can’t use those spaces for market crops, but as my Grandpa Jones once counseled, “Why would you want to plant a straight row when you can get more corn in a crooked one!” The point is, be aware of what’s already growing and take some effort to encourage and support the continued existence of such beneficial species when you can. It’s far less work to tend to volunteer plants than it is to get new species well established.

Ok. If we now move the dial a little bit off this far end of the spectrum, we’ll find ourselves at the option of leaving most of the cover crop in place and strip or spot planting your annuals into a field of cover crop. In order to keep our cover crops growing as long as possible and reduce the amount of time our soil sits bare between cover crops and annual market crops, we elect to transplant the majority of our crops instead of direct seeding them. This also really helps us manage weed pressure because our market crops have a big head start on fast growing weeds.

Typically we mow our cover crop, then use a disc to get the fibrous rye and grass roots decomposing faster. Sometimes we skip the disc and very shallowly till (4” depth, 30” wide strip on a 5 ft bed) with a walk behind tractor. We transplant directly into these strips. We use a post hole digger to dig holes for 4” transplants, and then we use a shovel to loosen the soil in each hole.

Then we add amendments to each hole as determined by the crop. After we transplant, we finish the beds by applying mulch around our transplants to cover the exposed soil and provide a healing protective layer to the soil we disturbed. This has the added benefit of keeping the soil cool and moist so you need to irrigate less. (Be careful, in the spring, you may need the soil to warm up, so wait to apply the mulch a few weeks post-transplant.)

Another benefit to this approach is that your paths are undisturbed and in the spring and late fall, that means not muddy. In addition, if you choose complimentary plant species (like low growing white clover), you have a source of nitrogen that keeps on giving! One thing to note- you’ll need to devote time to mowing the aisles. We use a small, push-type electric lawn mower. The good news? Every time you mow, you’re adding more organic matter to the system.

This method is primarily how we greatly reduce the negative impacts of tillage on our soil- both because we are strip tilling (not tilling the entire field, but only 30” wide strips) but also because we only till very shallowly and use manual labor to precisely prepare planting holes. We till, but we do it very thoughtfully and within the proper context of our system. We always make sure to offset the negative consequences of that disruptive practice by giving back to our soil so it can recover and heal quickly. That means we never mow, disc or till vast swaths at a time, and we always find a way to add back life-giving organic matter and living roots to our soil.

This past spring we were forced to try an extreme variant on this type of cover crop/annual crop system. Our seeding house was bursting at the seams because of prolonged rainy, wet weather, and our young broccoli and cabbage seedlings were fast outgrowing their soil blocks. We had to get really creative. There was absolutely no way we could till because the soil was saturated, so we improvised.

We used our lawn mower to mow the section very close to the ground. Then we used the post hole digger to dig big transplant holes directly into the living cover crop. It took a lot of patience and we had to significantly amend the wet cloddy soil we took out of each hole with a mix of our own potting soil and lots of compost to back fill the planting holes to make sure we weren’t over compacting the soil around the root zone of the transplants. I’m not going to lie. It was no fun, but it wasn’t a complete failure. Our yields were significantly lower and we had to more actively manage the grassy weeds between the plants. It wasn’t an ideal situation, but it taught us that this technique is possible. On a much smaller scale, there would be even more opportunity to fine tune this approach.

So there you go. A whole host of possibilities exist when working with cover crops. As you work to introduce cover crops into your gardening system, the best advice I can give is to be creative and keep learning. Take what worked each year and build on it. Dissect what didn’t work, and then compost those failed approaches and move on. Farming is iterative work. It’s taken me 15 years to develop my processes and every year we still make changes to make life better for the soil we steward, and the farm stewards too. I’m looking forward to hearing how your cover crop practices support your gardens next year.

Until then, may your blooms be bright, your roots be living, and your soil building rich and deep. ~AJ