The 17th annual Georgia Organics Conference was informative and eye-opening, and Dr. Elaine Ingham’s workshop on soil biology was one of the most-talked-about in the halls of the LEED-certified Jekyll Island Conference Center. The noted soil biologist emphasized that dirt—be it rock, pebbles, sand, silt, or clay—already contains all the nutrients any plant needs to grow.
Growers have long been laboring under the misconception that dirt is a medium to which we add nutrients to grow plants. The more we learn about plants, the more additives they need to grow, and we’ve spent the last half-century compiling a long list of nutrients and adding them to our dirt medium. According to Dr. Ingham, we may eventually discover that they require the entirety of the elements on the periodic table. But we don’t need to add these elements – they are already there. We just have to unlock them so that plants can use them to grow.
In healthy soil, beneficial life forms in the soil make nutrients available to plants. Plants release chemical exudates from their roots, then bacteria and fungi feed on these exudates and on dead plant material. The bacteria and fungi also solubilize mineral nutrients from sand, silt, and clay. When those bacteria and fungi are eaten by protozoa, nematodes, microanthropods, and earthworms, plant-available nutrients are released.
Unhealthy soil is soil in which the bacteria, fungi, protozoa, nematodes, anthropods, and earthworms that are necessary to convert nutrients to a plant-soluble form are no longer present. Life in the soil can be destroyed by spraying pesticides—the same harsh chemicals that kill pests above ground kill the life in the soil. This includes some organic pesticides and herbicides, derived to take the place of conventional chemical sprays. Tilling can also be devastating for soil life. Over-tilling the land compacts it. “Yes, it fluffs the dirt, the same way Hurricane Katrina fluffed New Orleans,” Dr. Ingham said. “But, similarly, it destroys all structure. Over time, this kills all the life in the soil.”
Nutrients are present in lifeless soil, but plants can’t access them. This also makes it difficult for roots to grow because plants have to put energy into building roots that they could otherwise put into growing produce.
There are many advantages to building a healthy Soil Food Web. The web increases plant-available nutrients – phosphorus is turned into plant-soluble phosphates, nitrogen into plant-soluble nitrates. Imagine never having to add these nutrients to your field again! It also ensures that nutrients are available in the amounts the plants need them. The plant communicates with the life in the rhizosphere through chemical exudates, and the life in the soil responds with exactly the nutrients it needs. There’s no need to worry about nutrient retention, because nutrients that are tied up in life forms can’t leach out of the soil.
Adding life back into your soil builds back structure destroyed by over-tilling. This improved soil structure increases root health and depth – tomato roots can grow as deep as fifteen feet in healthy soil! Have you ever seen that? The structure increases the soils ability to retain water, and it keeps the air and water moving. The beneficial life in the soil makes it hard for disease to survive there. It eats the plant exudates so that there is no food left for pathogens. It occupies space so that no room is left for undesirable organisms.
Replenishing the life in the soil will increase your yields, decrease your costs, and increase the nutrition of your produce. For a small operation, it could be as simple as inoculating the soil with beneficial soil life and nourishing the soil with compost. For a bigger operation, it might be a bit more of a process. But it will not cost you millions of dollars, and over the years it will save you time, money, and energy, and it will contribute to the health of your farm.
For more information, visit http://www.soillifeconsultants.com.