The soil food web refers to the living biology of the soil and how it impacts plant growth and soil structure. Most of the soil dwelling critters are things like bacteria, fungi, nematodes and protozoa which can’t be seen with the naked eye, but includes the things we can see like worms, springtails, and slaters. Bacteria and fungi break down and feed on inorganic mineral particles and organic matter in the soils, incorporating minerals in their bodies as they go. The nutrient is not available to plants in this form. As a plant grows, it absorbs energy through photosynthesis and carbon dioxide. Up to 40% of this energy gets sent to the plant roots and is exuded into the soil as proteins and sugars. The bacteria and fungi feed on these exudates and colonise around the plant roots. Nematodes and other organisms feed on the bacteria and fungi, releasing the absorbed nutrients directly at the plant roots, making it available to the plant. The soil food web depends on living plant roots exuding protein and sugars to feed on, and the plant depends on the soil food web delivering minerals to grow. Some microbes will live on inorganic matter alone, but there will be a bigger and more diverse community where there are living plant roots. A diverse community of microbes will make more nutrient available to the plant roots, effectively increasing the reach of the roots into different layers of the soil. Plant roots on their own have no ability to extract nutrient from organic matter, they are dependent on the soil biology to extract the nutrient and make it available in the root zone. Being a good organic gardener means being a microbe farmer.
I am writing to you to get your attention for a moment to tell you about a process that offers solutions to some of the major social and environmental issues of the day: third world poverty, nitrogen losses from soils (which pollute rivers and lakes), depletion of soil productivity, and above all climate change.
Here are two very different organic food growing systems which I love. One is an intensive urban, aquaponic, multi-level system, and the other involves doing nothing other than spreading wood chips and trusting nature. Yet both work and both are inspirational.