Soil is alive!
The sun shines down on our plants while our plants photosynthesize and produce food not only for themselves, but also for the microbes that inhabit the soil. In the rhizosphere (root zone) the plants’ exudates which consist of sugars, proteins and carbohydrates feed the microbes that inhabit that space.
The rhizosphere is a very busy place! Here, the plants’ exudates feed bacteria and fungi. These bacteria and fungi feed on the nutrients supplied by the exudates as well as the nutrients they have obtained from other organic matter and minerals (the sands, silts, clays) in the soil. Then they hold these nutrients in their bodies until they are consumed by predators. These predators are protozoa, nematodes, micro-arthropods, earthworms, etc. When bacteria and fungi are consumed, the predators are nourished and the excess nutrients are excreted as plant available nutrients. The plants’ roots take up these nutrients and the plant is nourished, too.
As long as the sun shines and the soil critters are cared for, our plants thrive!
Caring for the soil
Keeping the soil covered at all times with living plants is best. If that’s not possible, then cover the soil with compost and/or mulch. Doing this protects your soil from erosion and compaction and the microbes will be fed. The microbes in turn will create structure or aggregates in your soil so that both air and water can flow through. The soil will also be able to hold on to water like a sponge. As long as all the microbe groups are present (bacteria, fungi, protozoa and nematodes) then nutrient cycling will occur and your plants will be healthy and disease resistant. Also, remember to disturb your soil as little as possible. When you build up structure, why destroy it? Treat your soil gently.
It is important to look to the natural world for inspiration. In the natural world, the soil is never left bare. When leaves and twigs fall from trees, they are left to decompose with the help of microbes and other invertebrates. No one is plowing or tilling the earth other than earthworms, gophers, moles, etc. When these critters move the soil, they are creating airways, but are leaving the soil intact in most places. And, their excrement nourishes the soil life.
We, as gardeners, need to look at our systems in the same way. If we can leave plant debris on the ground where it falls, then do it. If we can’t then we need to feed the soil with compost and mulch.
When looking at a garden, I want to know the history. Has this land been tilled? Have fertilizers, pesticides, herbicides or fungicides been used? How much and how often?
Then I want to look at the soil. Is the soil crumbly? Does it have good aggregation? How does it smell? Are there earthworms and invertebrates there? Also, is there a compaction layer there? How does the soil absorb moisture? How does water drain?
Next, I take a sample of the soil and look at it under the microscope. Do I see bacteria, fungi, protozoa and nematodes? Are some missing from my sample?
If there are microbes that are missing, then I need to find the best way to put them in the soil. My tools are compost, compost teas or compost extracts. Different situations call for different approaches. It can take a while to change the biology, but once it is achieved, the plants will be more vigorous and healthy. Once the biology is there, if the soil is cared for, then the system can maintain itself in this healthy state.