The Dirt on Dirt
The best heirloom seeds can only grow to their full potential in healthy, living fertile soil.
"The soil is like a farmer's bank. You've got to keep making deposits into it all the time. If you withdraw from it until it's empty, you'll be out of business."
So what exactly is healthy soil? It is much more than just dirt with some compost and fertilizers mixed in. It is truly living- host to thousands of organisms in many communities that all do different things to provide the most available nutrients and minerals to the plant roots in the soil. It is in the soil where everything begins.
Everything that we need to grow and remain in good health starts with the health of the soil. This starts in the plants that we eat, and continues in our bodies. If we want the best benefits from our gardening efforts, we need to build and grow the best, most alive and healthy soil possible. Only then will we be able to grow the best gardens that will in turn give us the best taste and nutrition possible.
Mycorrhizal fungi could be the secret ingredient to making the perfect soil.
One of the primary principles of organic gardening is that of working with nature, using native resources and natural cycles to increase the abundance and health properties of the plants we grow. Many organic gardeners, however, are not acquainted with the valuable natural ally that embodies that core concept: mycorrhizal fungi. These unique members of the soil community are key players in numerous biological processes: helping plants take up more phosphorus, accumulating carbon in the soil, and improving its clumping ability. Mycorrhizal fungi don't accomplish these processes on their own; they work in concert with plant roots through the power of symbiosis.
In the organic system, soil is a living organism that provides nutritional support for people but also has nutritional needs of its own. For those who think of soil as nothing more than dirt, it may take an attitude adjustment to view soil as a living collection of creatures, along with minerals and bits of living material: iron oxides, unicellular bacteria, actinomycete filaments, flagellated protozoans, ciliated protozoans, amoebae, nematodes, root hairs, fine roots, elongate springtails, and mites.
All of these substances have an essential role in organic soil health and the quantity and quality of an organic garden's glory. They break down the huge, unwieldy proteins and lignins in straw, leaves, and the wastes and remains of living creatures into simple, accessible compounds, like nitrate and ammonium, that plants transform back into spicy peppers and mellow watermelons.
Get the underground army of mycorrhizal fungi to work in the garden by following a few simple management practices:
· If the soil is already high in phosphorus (a simple, inexpensive soil test can answer this), do not fertilize with a phosphorus-rich amendment, because high phosphorus levels inhibit development of associations between plants and mycorrhizal fungi. Manures and manure-based composts can be high in phosphorus, so test these amendments before adding them.
· Minimize digging (especially rototilling), as it can break mycorrhizal hyphae, preventing them from colonizing new plant roots and transporting nutrients.
· Grow a diverse mix of plants in your soil for as much of the year as possible, because mycorrhizae need active plant roots in order to develop.
Some techniques to keep the mix diverse:
· Rotate crops each year (as long as there aren't too many successive brassicas). Crop rotations are vital to mycorrhizal fungus populations because, in addition to providing a continuous succession of root hosts, different crops also tend to favor different species of mycorrhizal fungi.
· Plant an overwintering cover crop. In addition to adding organic matter and retaining soil nutrients, the cover crop offers host roots for the mycorrhizal fungi to colonize and helps them proliferate in preparation for next spring's planting. A good mix of crops above ground is the best way to support a mix of beneficial fungi below ground.
· Lighten up a bit on weed control, because, surprising as this may be, weed roots can also be excellent mycorrhizal hosts.
These simple, no-cost steps help keep the soil's native population of mycorrhizal fungi healthy and diverse, harnessing yet another gift of the natural environment to create a vibrant and abundant garden.