The Living Soil

I choose the title for this weeks newsletter to emphasize how important the health of your garden soil is. Soil is not just a bunch of little rocks, a spoonful of healthy soil contains many millions of beneficial microscopic organisms of various kinds that include beneficial species of bacteria, fungi, nematodes and protozoa that never cause disease or become pests. These are helpful species that perform vital "functions" in the root zone that can bring real benefits to your crops. Bacteria and protozoa are great micro-organisms in your soil. Bacteria break down dead organic matter. Certain types fix nitrogen (converting nitrogen from the air into a form plants can use). Protozoa are one celled organisms that feed on bacteria. They release soil nutrients by eating and digesting bacteria. Because they are single celled, they can attack bacteria in small pores that nematodes can't get to. They can also be used as indicators of soil conditions. The more abundant and the more species of protozoa found in your soil, the better the condition of the soil is. Fungus are common micro-organisms in soil. Most people think of fungus as only "bad." But that's just not true. Fungus do not use sunlight to make energy. Instead they use chemical reactions to create their energy. They get material for these chemical reactions from dead organic matter, including cellulose, the stuff that makes plants woody. Cellulose is tough stuff, but fungus can break it down making those nutrients available for other organisms. Without fungus, a lot of nutrients would be tied up in un-decomposed woody matter. Bacteria and fungi are extremely rich in protein that is made from nitrogen. I think it is interesting that as bacteria and fungi multiply they gather up free nitrogen from the soil and convert it to protein in their bodies. The rich meal of protein is metabolized and released back into the soil as ammonium that is quickly converted to nitrate for use by crops. The organisms that perform this function are beneficial nematodes that only feed on bacteria or fungi, the protozoa that feed on bacteria, and beneficial soil mites that feed on fungi. As these species go about their work they cause nitrogen especially, but also phosphorus and other nutrients, to be released at a gradual rate that supplies crops with a steady diet all season long.

In addition to various microscopic organisms, the carbon, the minerals, and the organic matter, we find a whole host of macro-organism, or those you can see with your naked eye. They live in and on top of healthy soil. These include worms, snails, slugs, wood lice, beetles, termites, ants, millipedes, and centipedes. Some stay near the surface and eat the litter that drops to the ground. Some, like worms, can be found quite deep. Some of these soil creatures eat litter, but don't absorb a lot of the material. What comes out is politely called castings and is rich in biological activity. By grinding and chewing the plant litter, these insects increase the surface area available for bacteria and other micro-organisms to break down the material. These macro-organisms also provide food for predators such as birds, toads, lizards, and spiders. These predators in turn will also eat pest insects. Worms are great for the fertility of soil. Worms traveling through the soil are the delivery trucks of the underworld. They distribute organic matter, bacteria, slime molds, fungus, nematodes, spores, pollen and seeds. When worms move through the soil, they increase the amount of water that can percolate through it. Their castings increase the pH of the soil. Their urine and mucus release nitrogen in to the soil. When they die, their bodies release more nitrogen in to the soil. You definitely want to encourage these creatures to live in your soil. So what can you do to obtain the balance of healthy soil?

To create good soil you need to start with organic matter to add nutrients to your soil. It should be your first step because organic matter does provide carbon, but it also improves the "tilth" of the soil. Organic matter holds water and nutrients, provides habitat for microorganisms and counters topsoil erosion. Just adding organic matter to the soil is not enough. You should stop using chemical pesticides, herbicides, and fertilizer, and stop rototilling. There is a growing movement toward biological controls instead of using chemicals. Organic Gardening has been a proponent of this for decades. Nature has always had it own control mechanisms, but we chose to ignore that and use the fast chemical to kill pests. Integrated Pest Management (IPM) is a good example of science using what nature has always had. You focus on saving predators of bad bugs. Sometimes it's even mentioned that you should rotate your use of these chemicals because the offending organism will develop resistance. It seems that all the chemicals that we have been adding call for more chemicals to get back to the balance we had before we started adding chemicals. Once you stop using chemicals, nature will clean up the carry over of herbicides or pesticides. Most herbicide and pesticide molecules can be "eaten" or degraded by certain kinds of microbes in the soil, if those species are present. A healthy soil will tend to rid itself of chemical carry over and other forms of pollution.

Stop using inorganic fertilizers. You'd think this would be harmless. Just a few green crystals and your plant will be so much happier. However, those crystals are heavy on the salts, discourage earthworms and soil microorganisms, and only provide major nutrients. They don't feed the soil either. The nutrients give your plant a short term boost, but the fast lush growth is a magnet for bugs. Then you end up spraying and using pesticides - organic or not. Excess nitrogen can decrease the number of flowers and fruits your plants produce. Inorganic fertilizers can contain heavy metals and other dangerous ingredients. There is very little regulation of so called "inert" ingredients in fertilizers. Your much better off with natural slow release organic amendments and compost. These provide not only major nutrients, but trace nutrients in a natural setting your plants can use over extended periods of time. Plus, by using a balanced approach, your plant will not have that burst of growth that can lead to increased susceptibility to disease and insects. You should be feeding your soil and not your plants. Your plants know how to feed themselves.

Soil structure and tilth can be ruined  by excessive rototilling. Enjoying the very best tilth depends on maintaining an aggregated or crumb soil structure. This is the ideal  soil structure that allows for the optimum infiltration of air,  water and roots systems. Don't till your soil. Tilling destroys soil structure, burns up organic matter and kills  microorganisms. To preserve healthy soil, cover your soil at all times. Either have mulch or plants on your soil at all times. Sun and water will wash away and destroy nutrients and soil structure. Healthy soil is like good food. People thrive on variety in their diet, and plants thrive on variety in their soil. Plants evolved in soil teeming with life; therefore, it's not surprising they do well in living soil.


You can test your soil and discover which type of soil that you have. Take 1 cup of cleaned soil (no sticks or rocks) and put in a 1 quart mason jar. Make sure it has a tight fitting lid. Add water until you have 1 inch of head space and put on your lid. Shake it up until the soil is dispersed in the water. Let it sit for 24 hours and then measure the layers. The bottom layer is sand, the middle layer is silt, the top layer is clay. Sandy soils are 65-100 percent sand. Loamy soils are 25 - 50 percent sand, 30 - 50 percent silt and 10 - 30 clay. If you see at least half of the total is the clay layer, then you have clay soil. 


 "Green fingers' are a fact, and a mystery only to the unpracticed. But green fingers are the extensions of a verdant heart. A good garden cannot be made by somebody who has not developed the capacity to know and love growing things."




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