by John Jeavons, Master Gardener, Author and Executive Director of Ecology Action
©Ecology Action 2016
As the summer crops begin to slow down and come to the end of their life cycle, and the day length starts to shorten, it’s time to start getting your garden ready for winter. While not much grows during the cold season, having crops in the ground is an important way to ensure your soil is healthy enough to provide next years abundance.
Cover Cropping is one of the best ways gardeners can take care of their soil, by growing large amounts of compost materials and a significant amount of calories, while “covering” the soil for the winter, and we at Ecology Action have been doing continuous research on this particular technique since 1972. There are many benefits to getting a crop into the ground before winter arrives with heavy rains and cold frosts. Here in our climate, having all the cover crops in by November 15th is ideal—this allows the crop to establish itself but not get too big before the rains come, which could cause them to fall over.
Some of the main benefits of having cover crops in your crop rotation are:
Maintaining soil fertility
While adding compost is a fantastic way to build up organic matter in your soil, having living plants growing, and roots in the soil is even better. Most of the biological activity in the soil happens in the zone closets to the roots, known as the rhizosphere, so having a crop in the soil year around allows the continuation of this microbial activity, even though it slows down in the winter. It is this relationship between the microbes and the plant roots that make nutrients available to the plant. With biologically intensive methods, including close plant spacing, we are able to grow more plants in a smaller area–even more roots, and better nutrient cycling!
Growing Biomass for Compost
In a GROW BIOINTENSIVE® system, one of our main goals is to make sure enough biomass is produced to grow all of our own compost and calories. By taking advantage of winter crops, such as winter grains, we can ensure that we will have enough biomass to build our compost in the spring, as well as producing sufficient calories to eat. These winter grains (as well as summer grains) are what we refer to as “carbon crops”. By having 60% of your garden in high yielding, carbonaceous crops, not only can you grow all your compost materials and much of your calories, but you are also able to sequester CO2 from the atmosphere and put it back in the soil where it belongs.
Sustaining the Moisture Content
Having a compost crop in the soil during the rainy season allows the soil to maintain its ideal moisture. Organic matter and roots in the ground can help retain water and keep the moisture content balanced. If a bed is left fallow and is heavily rained on, the soil could become over saturated and compacted, which would affect the quality of the soil long term and make it more difficult to work later on in the spring, thus, prolonging the planting of your spring crops.
Having roots in the soil makes it less likely to be lost due to winter rains and harsh winds which can dry out and move the soil out of the garden bed. The roots help prevent the leaching of nutrients out of the soil, and it can even increase the soil’s nutrient content.
Preserving Soil Structure
Maintaining good soil structure is key to growing good, healthy plants. When referring to soil structure, we like to use the acronym A.W.O.M.B. (Air, Water, Organic Matter, Minerals, and Biology). Having roots in the soil through cover crops can help break up soil compaction, which happens from heavy rain fall. By breaking up the compaction and creating better pore space, more oxygen can be introduced to the soil and the roots, water can penetrate these pores, which is key to microbial life and nutrient cycling for the plants. If you want to have a healthy garden, the first thing you need to pay attention to is the health of your soil.
Garden beds frequently planted with cover crops will have fewer problems with weeds. Close spacing of winter grains creates good coverage of the soil, which will shade out most weeds. Having the cover crops planted close together also allows for them to contain the weeds that would come up in the spring. So, not only can you get more biomass and calories from these crops, you also create less work for yourself in the coming season!
What crops to grow?
Depending on your climate, when it comes to picking crops that will stand up to winter there are two main families that we like to grow—winter grains which display the benefits previously mentioned, and appropriate legumes. Legumes exhibit an additional unique benefit—they are able to take nitrogen, a critical component to plant life, from the air and rain and store it in the soil. This unique capability of leguminous plants is made possible through a symbiotic relationship to a bacteria called rhizobia, which only attaches to the roots of legumes. The rhizobium converts the otherwise inaccessible nitrogen from the air, and makes it available for the plants to use. Nitrogen is one of the most common deficiencies in soils around the world. The attempt to remedy this deficiency through the introduction of nitrogen rich fertilizers into the soil has some severe consequences to the environment.
I choose fava beans as one of my main legumes for cover cropping as they can get really tall (more carbon, more biomass) and we get incredible yields (more calories) while fixing nitrogen into my garden bed. Another favorite is wooly pod vetch, which can fix up to three times the nitrogen in comparison to other legumes.
Some of the best winter grains to grow are rye, because of the amount of biomass it can produce and their ability to grow a large root system deep in the soil. One single cereal rye plant puts out 3 miles of roots in a day! Barley, triticale, and wheat are other favorites. A person can actually grow enough wheat to make a 1lb loaf of bread and two large bowls of oatmeal, once a week, in an area as small as 300 square feet!
To maximize the benefits of cover cropping, we actually like to interplant our grains with a legume—wooly vetch, being great for that.
Start Planting Today
As you can see there are many reason to grow winter and fall crops—you can improve your soil fertility, grow healthier plants for seasons to come, and help remove carbon from the atmosphere. Begin planting today! Experiment what works best in your garden. You can talk to other gardeners in your area about what crops grow best, and when to plant them, as well as checking with your local Agriculture Extension Agency. To find out more about how to grow healthy soil and the GROW BIOINTENSIVE system, check out our website www.growbiointensive.org. You can also attend Ecology Action’s upcoming three-day workshop to learn more, or browse through our publications at bountifulgardens.org. Happy Planting!