Soil Health, Part Two
Jim Chamberlin, Happy Dancing Turtle’s Conservation Technician, with his wife, Audra, operates a 109-acre diversified farm and forestry operation near Deerwood, MN, . His knowledge about and enthusiasm for what we can do for soil and what soil can do for us will fuel this four-part series of blog posts.
In the previous blog post, we introduced the first principle of soil health, Minimize Disturbance. Soil health is defined as the “ability of soil to function as a living ecosystem.” In this post, learn more about the second and third principles, keeping in mind that all the soil health principles are relevant and important:
Minimize Soil Disturbance
Armor the Soil
Keep Living Roots in the Soil
Manage for Context
I was listening to a presentation by Joshua Dukart at the Northern Plains Sustainable Agriculture conference. Mr. Dukart is a Certified Educator of Holistic Management with the Burleigh County Soil Conservation District in North Dakota, one of the first regions of the country to adopt the soil health principles. He was telling the story of how one day the then-District manager, Jay Fuhrer, came in from the field and started ranting, “They call it crop residue, trash, and litter. It’s way too important for names like these,” Fuhrer claimed as he went to his office and slammed the door. He emerged a few minutes later, pounded his fist on the table. “We’re calling it armor; it’s that important,” he declared. As a past SWCD employee I understood the passion for conservation and could only imagine the conversations these pioneers of soil health had...to be a fly on the wall.
Soil organisms are living beings and need favorable conditions to survive and thrive. Soil without armor leaves it open to erosion, large temperature extremes, and loss of moisture to evaporation. Soil covered with living plants can be as much as sixty degrees cooler than bare soil on a hot, sunny day, protecting the organisms that live there.
Effects of raindrops hitting bare soil
dis-lodges the finest soil particles causing erosion
plugs soil pores preventing soil air exchange
causes soil crusting which inhibits water infiltration and seed germination
Benefits of mulch and living plants
preserve soil moisture
protect soil life
Cover crops are increasingly being used by farmers to protect and armor the soil. Some regions of the country are seeing cover crops utilized on upwards of 30% of cropland. Cover crops are typically seeded into established cash crops where they germinate and growth is suppressed under the canopy. Once the crop is harvested the cover crop is released and grows rapidly. Other producers are planting perennial crops or transitioning to perennial grazing systems that keep the soil armored year around, and year after year.
Armoring the Soil for Gardeners
One method for gardeners to keep their soil armored is a deep mulch method. Hand dug beds, six inches tall and 3-4 feet wide, are dug and covered with several inches of straw or old hay. To plant, the mulch is moved to the side or on the walkways. Beds are top dressed with compost and soil amendments in the fall and remulched. Every two or three years the walkways are redug, placing the soil from the walkways on top of the raised beds and the beds raked level, then covered with another generous layer of mulch.
Annual cover crop species or those that freeze out over winter are another way to keep small garden spaces protected. If planted late enough in the season they don’t have a chance to go to seed and become a weed issue, though with most cover crop species I haven’t found this to be an issue. Underseeding crops like squash or seeding in between rows of vegetables is another way to keep the oil armored. Perennial cover crops can be used for long term soil protection in certain rotations.
“Chop and drop” is a method of weed control where weeds are cut close to the ground before going to seed and left as mulch in the garden. This typically works best with annual “weeds” and not with perennials such as quack grass. Some species, especially those with hollow stems at maturity, like cereal rye or buckwheat, can just be walked down at flowering stage leaving a living mulch to protect the soil. While not totally effective at killing the plant, it sets the plants back and is a simple form of crimping.
Example annual cover crop mix (seeded 45 days before first frost)
Percentage by weight: 32% oats or barley, 32% buckwheat, 32% field peas or soy beans, 1-4% field turnips or radish.
Dr. Elaine Ingham helped the Natural Resource Conservation Service (NRCS) to publish the Soil Biology Primer in 1990’s as an “introduction to the living component of soil.” Dr. Ingham and this little booklet were driving forces behind the soil health initiative of the NRCS. I was able to hear her speak at the MN Organic conference several years ago.
Ingham explained how plants exude a snot-like substance from their roots. This “plant snot”, or plant exudate, serves as a primary food source for microorganisms in the soil, mostly specific bacteria that live close to the root of the plant. The organisms that feed on this substance are in turn eaten by larger bugs, she went on to explain. And when those organisms die or defecate, they provide minerals and nutrients in the right form and balance that the plant needs to grow. This isn’t new science. In 1904, Lorenz Hiltner, a pioneer in rhizosphere microbial ecology and soil bacteriology research, wrote of the “Unique population of microorganisms influenced by the chemicals released from plant roots.” Plants feed the soil life and the soil life in turn feeds the plant life.
Keeping living roots in the soil helps ensure a steady supply of this plant exudate to feed the microbiome in the soil. Living roots also support mycorhize fungi, a type of fungus that attaches to plant roots and forms a symbiotic relationship with the plant. The plant feeds the fungus, and the fungus converts nutrients to a usable form and feeds them to the plant. Without living roots, the soil food web suffers.
The Role of Cover Crops
Cover crops are the main tool to keep living roots in the ground for crop and vegetable farmers. Not intended to be harvested, they are inter-seeded into existing cash crops so once the crop is harvested living roots remain in the soil.
Perennial plants have an important role to play in building soil health as well. These could be grasses and forbs in a rotation with crops, or woody plants such as brambles and fruit or nut trees planted in a diverse agroforestry planting. Plants that readily reseed, like dill, borage, and lettuce can be left to go to seed. Biennials that overwinter are another way to keep living roots in the ground. Examples include garlic or parsnips. Spinach started in the fall will often overwinter in a hoop house or under heavy mulch, then begin growing in early spring after the frost is out of the ground.
Cutting or mowing weeds (chop and drop) before they go to seed can also be a way to keep living roots in the ground. Just be careful that they are weeds that are easy to control. Any method you can find to keep roots in the ground longer in the growing season the healthier your soil will be.
In the next blog post, learn the two more soil health principles, Increase Diversity and Integrate Livestock. In the meantime, when you're in farm country, try to spot if a cover crop is in use, or experiment with planting cover crops yourself. Small grains such as barley and oats, or brassicas are a good cool season cover crop that can be seeded well into September and will grow late into the fall. Or they can be frost seeded on frozen ground in late winter. Find out more on planting cover crops with vegetables here.