Cover cropping is a soil amendment system that GREATLY improves our soil’s structure and overall fertility.
And, contrary to popular belief, cover cropping is simple for the backyard gardener, despite how difficult it might seem! Basically all we do is seed tons of plants in our beds toward autumn, let them grow and leave them completely alone all winter, then gently mix their decayed foliage and roots into the soil in the following spring as green manure.
The truth about cover cropping = the plants do most of the work!
Traditionally synonymous with organic farming, cover cropping is absolutely a practice we can adopt in our own backyards, even in raised beds that are just a few feet long! By selecting the proper cover crops for your space and timing the seeding right, a wealth of benefits (all given by nature herself!) await.
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How Cover Crops Work + Why We Use Them:
- – Cover crops break up hardpan soil with their incredibly strong root systems (alfalfa, mustard, daikon radish, rapeseed);
- – As cover crops decompose over winter, foliage and root systems feed a diverse variety of microbes and the thick layer atop the soil surface protects your soil from the harsh cold winter;
- – Root systems experience cycles of growth and decay, leaving behind a plethora of rich humus deep underground (and extra humus and organic matter means the soil has the ability to hold way more moisture! This is imperative in areas of drought);
- – Legume cover crops (clover, field peas, vetch) fix nitrogen from the air and deliver it to their roots in small nodules, replacing nitrogen that was used up during the growing season;
- – As they are incorporated back into the soil in the spring as Green Manure, decomposed cover crops add tons of organic matter to the top layers of soil, along with tons of food for Soil Food Web organisms;
- – Many cover crops produce beautiful flowers that feed pollinators!
Also, I have a 2-part blog series on soil building techniques here: Increasing the Biodiversity of Your Soil Food Web: Part 1 and Part 2. If you really want to learn what it takes to build healthy soil and increase productivity in your garden (without raised beds!) I suggest bookmarking these articles and start implementing the practices in stages.
Here are 4 steps to cover cropping your backyard garden, no matter if you have one raised bed or an entire acre of land…
1. Choose Your Cover Crop Varieties
- Similar to polycultures: More variety of cover crops = More variety of soil microbes = More nutrient availability for our veggies! Each cover crop secretes their own unique concoction of sugars in the soil, which feed the fascinating, invisible microbial world!
My method for choosing cover crops is really simple: Choose 3-4 different types of cover crops, mix them up together in a bag, and sow them all together.
To address multiple issues, I recommend choosing one cover crop from each category:
- Break Up Hardpan Soil: Alfalfa, Mustard, Daikon Radish, Rapeseed
- Fix Nitrogen: Crimson Clover, White Clover, Field Peas, Common Vetch, or any leftover bean or pea seeds
- Add Carbon to Balance Nitrogen: Ryegrass, Annual Fescue, Winter Rye
One More Easy-Peasy Tip (see what I did there) – Essentially anything can be a cover crop…
So if you have an excess of any seeds, feel free to try using those (I’ve used arugula and sweet alyssum!) Just make sure you have 3-4 different types of seeds in the mix, including one nitrogen-fixing legume. This Cover Crop Growing Guide is very useful and visually displays a ton of options – as long as you pick a few different crops, they will serve their purpose in your garden. Have fun with it!
2. Seed Your Cover Crops at the Right Time
Seed your cover crops toward the end of the growing season. In the Midwest (Zones 5-6), the time to seed cover crops is Early September-ish – but make sure to check your frost dates and germination times of your cover crops. Johnny’s has really great info on each cover crop seed page.
No matter what growing zone you live in, you want your cover crops to be planted early enough so you get a good amount of green growth before your frost – about 12-18″ in height.
Proper timing will allow the cover crops to grow enough of a root system, and enough green foliage to cover the soil before going to seed. If you think your cover crops will go to seed before the frost, simply cut them down, but be sure to leave all that good green stuff right where it is. Point is to prevent them from seeding themselves all over the place, unless of course, you have a larger farm and that is your intention!
Seeding cover crops 1.5 to 2 months before the end of your season means most of your vegetable plants will still be growing! Some might even be thriving, and this is quite alright! Simply sow your cover crops around your existing plants. Some seeds may not germinate if the sunlight is blocked, but that’s okay. Even a little bit of cover crop growth will make a difference in your garden.
If you have a large garden and plan to leave a few beds fallow during the growing season, consider cover cropping them starting in the spring. You can do this by sowing a round of cover crops in the spring, chopping them down before they go to seed, and then sowing another round of different crops afterward. Do not remove any of the plant material between seedings, this green manure holds tons of precious nutrients that should decay back into the soil.
3. Shut Your Garden Down Leaving Cover Crops Untouched
- The cold has arrived and you’ve decided to clear your garden of your frost-bitten vegetable plants. Most people approach this by pulling all of the plants out by their roots, but I encourage you to not do this. Rather than pulling them entirely out, do the Chop ‘n Drop, which leaves root systems behind and entirely in tact.
- By electing to leave your veggie root systems in place, you have just provided your soil microbes food for the entire winter! Gosh, what a gentle, lovely human you are. The roots will also hold your soil in place and prevent erosion. For smaller green plants (such as lettuces, spinach and arugula), you should leave them entirely in the garden, dead foliage and all. Leaving them be will allow the plants to decompose over the winter into valuable organic matter. Your veggies just became cover crops! As for your actual cover crops you seeded separately: Treat them the same way. Do not pull them out or cut them at all – You have grown them for both the roots and the foliage so they should be left untouched to overwinter.
4. Incorporate Your Cover Crops During Spring Soil Prep
Fast forward through winter (brrr! boo! hiss!) and now it is spring and time to prepare your soil. So what do you do with all of this leftover plant matter in your garden? Your first instinct might be to rip it out and compost it – Stop right there!
Rather than ripping all your cover crops out, you will incorporate all of that awesome decayed plant stuff back into the soil. It’s the whole point of cover cropping in the first place!
To prep your soil with decayed cover crops, you will gently dig them in with a spade or, as I prefer, this awesome compost fork. You absolutely will not use a tiller to prep your backyard garden – if you are unsure why, read my article on Part 1 of Building Healthy Soil and Increasing the Biodiversity of the Soil Food Web. Try to “twist” the cover crops down into the soil rather than flipping the soil over onto itself – flipping the soil over will expose microorganisms to the air and oxidize them. Gentleness is key here.
Some of the leftover roots from the larger plants might need to be removed, but do so with care. Once you’ve pulled the large roots up, consider cutting them up with your pruners and adding the pieces back into the soil. Any leftover bits of decayed cover crops can be seeded and transplanted into, and then it should all be covered up with mulch once the seedlings are established.
PS. The whole point of leaving roots in tact is because MUCH of the soil microbe activity happens in the rhizosphere, which is right at the plants’ roots!
Once you have nurtured your soil microbes and have restored your garden back to her original, biodiverse fertility, there is very little you will need to do in terms of yearly soil preparation. Disturbing the soil, needlessly aerating it year after year with machines – this is a finicky, unnecessary step to soil prep invented by humans. Good gardeners know this and live by this. If we take care of our microbes, they will take care of themselves and us.