The plant-microbe symbiosis is a sophisticated system based on needing each other. In conventional agriculture, you feed the plants directly with chemicals; the plant does not need microbes, so it does not nurture them, and you have a microbe-deficient soil. Microbes do more than feed the plant the nutrients you used as fertilizer, or that they manufacture — they build soil structure, support plant immunity and mine micronutrients in the soil for your plant. When you don’t rely on chemicals, you’re going to be reliant on microbes to feed your plant, and the microbes will build soil structure, mine nutrients for the plant and protect them from pathogens.
We have recently discovered that rhizophagy is an important way that bacteria deliver nutrients to plants. The plant puts out exudates that bring in the microbes it wants to inhabit the rhizosphere. These microbes are often referred to as plant-growth-promoting bacteria because they stimulate plant growth. Bacteria in the rhizosphere enter the root. As they migrate up the root, about 40 percent of their nutrients are extracted by the plant. In return, the plant gives them carbon and forms root hairs through which the bacteria can reenter the soil. Dr. James White has shown that plants that do not have these plant-growth promoting bacteria do not form these important root hairs. He has also shown — and other studies have shown too — that a plant can get 40 percent of its nitrogen, as well as other nutrients, through rhizophagy.
