By Kay Wolfe
Knowing how to revive soil and encourage beneficial microbial growth are keys to healthy produce. And it can be done with organic gardening.
Organic food has become widely popular in recent years and in part has fueled the success of local farmers markets. Maybe you’ve even thought about switching over to organic methods in your garden but weren’t sure how to begin. Most people go organic to avoid pesticides and other chemicals in their food, but the result of using natural organic methods is your soil once again comes alive the way nature intended. There are amazing benefits to live healthy soil, both to the plants as well as to the environment. Let’s try to simplify this in layman’s terms.
Organic simply means something derived from living matter and nothing is teaming with life more so than healthy soil. Not all soil is healthy though. In fact, for a long time, we’ve been destroying our soils faster than they can recover. Before man challenged the Great Plains, the soil there was several feet deep and held a diverse collection of plants and animals. How and why the soil was so deep and productive should be of great interest to us if we ever hope to make it so again. The tide is starting to turn though with more and more gardeners going organic and learning how to revive soil.
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The next time you’re in a forest, push aside the leaves and dig down to get a handful of dirt. Feel how light it is and then smell the sweet earthy aroma of healthy soil. This is nature’s way and this is what we should aim for. The most active soil life lives in the top four inches so when you leave it uncovered and expose it to the sun or rain; you are destroying the microbes, which make up the life of the soil. When you take your tiller to your garden, you are doing even more damage as you destroy the fungi webs, the worm tunnels, and the very structure of the soil. That is man’s way, not nature’s.
With the advent of much-improved electron microscopes we can now see what lives in our soils. Healthy soil samples like that on the forest floor can contain more than a billion bacteria, thousands of protozoa, several yards of fungal hyphae, and dozens of nematodes including hundreds if not thousands of different varieties of each. In addition to the microscopic beings, there are also countless varieties of arthropods (bugs), earthworms, gastropods, reptiles, mammals and occasionally birds that become part of the food web.
We call it a food web because it is not a direct food chain where nutrients are moved up to larger species. The nutrients go back and forth from species to species. The organisms all tend to eat each other at different times and under certain conditions. But, the result of all this eating and growing changes the nature of the soil as microbes protect, feed, and improve the plants. Let’s look at the workers responsible for what makes good soil.
Bacteria and archaea are the smallest microbes in the soil and comprise the largest number of all living soil organisms by far. We tend to fear these one-cell life forms as the source of disease and infection, but in reality, life would be impossible without bacteria in the soil as well as in our own bodies. There are more species than we can count, but only a portion of them are harmful. Bacteria decompose organic matter using enzymes to break down the cells into individual minerals and nutrients, which they store in their own bodies until needed by the plants. If not for their ability to store them, the minerals and nutrients would be washed away after a rain or released into the air. Bacteria also create a slime that holds the soil particles together and buffers the acidity of the soil. This is how they improve soil texture and water-holding capacity. Their size limits their mobility though and most spend their life within a few inches if they don’t catch a ride somehow.
Fungi are the second most abundant life form and decomposer of organic matter, but they are much bigger than the one-celled bacteria. Yes, mushrooms are fungi, but I’m talking about the nearly one million varieties that live underground forming large webs of filaments or thread-like hyphae. These hyphae can prey on other life forms like damaging nematodes and bacteria and can move great distances, relatively speaking. They can go above ground to reach dead leaves or they can go deeper into the ground. They are able to eat woody particles that bacteria can’t because they have stronger enzymes. But, like the bacteria, they store nutrients in their cells, protecting them from leaching and bring them to the root zone like extensions of the roots. Fungi tend to acidify the soil through this process while bacteria buffer it.
Moving up in size we have the protozoa, including the amoebae, ciliates, and flagellates. Protozoa both feed on bacteria and other life forms as well as provide food for them. They benefit the plants by producing nitrogen in a form preferred by individual plants. They also provide a way for bacteria to move and they are food for worms and other higher life forms.
Nematodes are tiny round worms that eat their way through the soil. Some are beneficial while others prey on plant roots. Their biggest benefit is they release nitrogen gained from eating and digesting the nitrogen-fixing bacteria so it is available for the plant at their root zones. Healthy soil is balanced with the detrimental bacteria and nematodes held in check by the beneficial fungi, bacteria, and other life forms. The result is healthy productive plants without any aid from man.
Arthropods as a group are what you and I call bugs. While we may not like them, we certainly need them. Arthropods that live in the soil take larger pieces of organic matter and chew it up so the bacteria and fungi can begin to break it down. They also improve the structure of the soil by tunneling and act as a taxi for other smaller life forms allowing them to move throughout the soil. Although they are huge compared to bacteria, most soil-borne arthropods are too small for us to even notice.
One of my favorite life forms in the soil is the earthworm. Even before I began to study soil, I knew that earthworms were good for soil and the more the better. They are small but oh so powerful. Just an acre of good garden soil contains enough earthworms to move 18 tons of soil a year in search of food. Just think what they could do for compacted dirt! They will eat just about anything they can get in their mouth but their primary source of food is bacteria, so when you see earthworms, you can feel confident that you have a good supply of beneficial bacteria. The castings they leave behind are rich in phosphates, potash, nitrogen, magnesium, calcium and many other nutrients that feed your plants. Their burrows open up the soil so it can breathe and helps direct water where needed. Roots often take advantage of the canals and grow in this nutrient rich environment.
The Soil Food Web
As a gardener, you already know it takes more to grow a plant than the sun. It takes water, minerals and a lot of nutrients. Until now, how that plant got nourishment was somewhat of a mystery. It gets it through the roots mostly except for a small amount of foliar feeding (feeding through the leaves). Many people just assume the roots absorb the nutrients from the soil, but the actual process is much more complex than that. Since roots are stationary, they can only absorb what touches their surface so it is up to the microbes to make sure they have access to the nutrients they need, in the form they need it, and when they need it.
Plants and the soil microbes communicate in order to help each other in a symbiotic relationship. Plant roots leak a sweet substance called “exudates” that attract fungi and bacteria. In return, they supply the root with nutrients they have broken down through their enzymes. Beneficial fungi can actually reach out through their hyphae and transport nutrients back from one plant to another as in nitrogen transfer between legumes and non-legumes. The microbes are like little armies of servants protecting the roots from invaders, providing water and nutrients when needed, keeping the soil open so oxygen is present, and keeping the soil structure and pH in the proper balance.
Chemical fertilizers, pesticides, herbicides and all the other “cides” are poison to the soil microbes. Oh, it works for the short term because a bit of the fertilizer touches the root hairs and is absorbed, but the majority of it is washed away while killing the microbes. Your plants stop secreting exudates because the soil life is no longer there to take care of the plant’s needs. Soon they are overcome with disease and pests, which only causes us to want to use more chemicals. It’s a horrible cycle and it is what has ruined much of our soil. The next time you drive by a non-organic corn field, stop and take a handful of the dirt and study it. This is what dead soil looks like and it will end up compacted no matter how much you disc it. It will dry out in a short period of time and it will heat up fast and crust over. None of which is beneficial. Now compare that to the sweet earth from the forest.
Soil compaction is a huge problem with dead soil. Think of a ream of copy paper. It is hard, heavy and tightly spaced. Now, if you begin to take each page and crumple it and throw it in a box, soon you have a soft fluffy pile of paper. That’s what life does to soil. It opens it up so the roots can penetrate easily and deeply. It holds water not as mud, but more like a sponge to be used later. It stays cool and moist even in the heat of summer. That is what organic gardening and soil microbes can do.
How to Revive Soil That’s Dead
So, how can we bring life back to our soil and improve it in a sustainable way? Well, the first thing we need to do is stop the killing and that means no more synthetic chemicals. None. Things may get worse before they get better, but the life will never come back until you stop the poison. There are a few basic organic gardening tips and once you get them down, gardening will be easier than it has ever been.
• No till—When you lay the ground open you lose a big part of your carbon and nitrogen to the air. Poof! Your nutrients are gone. Since most microbial life is in the top four inches, you just wiped them out as a tsunami or a tornado would do to a village. Get rid of your plow; get rid of your tiller so you will never be tempted to use them again. Make no bigger hole than needed to plant your seed or set out your plant. A technique I like to use is to cover the seeds with a layer of rich compost rather than disturbing the soil.
• Mulch—Nature hates exposed soil because it knows it means certain death to the microbes that live just below. No matter how many times you cultivate or hoe, nature will fight even harder to cover it with the fastest growing thing she has and that is a weed. Covered soil holds moisture longer and it doesn’t erode in heavy rains. It also keeps the temperature more constant whether in winter or summer which protects your plant roots as well as the microbes. Organic deep mulch gardening provides a constant supply of nutrients for the organisms to consume and break down, further improving your soil. I like to cover my beds with cardboard or newspaper around plants to keep the weeds from germinating and then top with a mulch of alfalfa hay, but you can use whatever organic matter you like.
• Keep it growing—Don’t waste space. Use permanent wide rows, square foot gardening, or any method you like as long as you keep living plants on the soil. That means use cover crops and there are many to choose from. They will keep the soil covered and add organic matter to feed the microbes once you turn them into mulch. You might want to mow them or weed-eat but leave the plant material where it grew. Studies have shown that hairy vetch grown before tomatoes and then left as mulch increases tomato yields substantially. I’m sure there are many other combinations that could work just as well.
• Feed your soil—There are simply too many organic choices to ever need chemical fertilizers. The best way to feed your soil, thus your plants, is with compost and/or compost tea. There are many books and articles on how to revive soil so I won’t go into it here, but remember that fungi favor the brown (bark, straw, saw dust) while bacteria favor green (grass clippings, garden waste, kitchen scraps, etc.). Since fungi create elaborate webs of hyphae, long-term plants such as trees, shrubs, and perennials benefit more from them while annuals and vegetables prefer more bacteria. You can create compost specifically for the kind of plant you are fertilizing by adjusting the percent of green and brown in your compost.
• Stay off the soil—Once you begin to bring life back to your soil and the microbes begin to fluff your dirt, don’t go and crush their tunnels and destroy the structure by walking and driving over it. Make permanent beds with paths to use for foot traffic and wheel barrows. Compaction smothers the oxygen out of your soil, kills the life, and causes irrigation and rain to run off without doing your plants any good. I prefer raised beds for many reasons, but one thing it does is discourage pets and people from stepping in the beds.
• Pest control—As your soil life gets better, your plants will become healthier and can ward off pests and disease, but if you find you still need help, check out the organic products for the particular problem you have. I have found that many times an infestation left alone is soon conquered by beneficial insects or birds. Some plants need more help than others though—such as fruit trees—so become familiar with organic products ahead of time so you are ready when they attack. I personally don’t aim for a perfect plant or produce. I plant enough to share with nature as long as they don’t get too greedy.
The earth has a remarkable ability to heal in spite of the harm done by man. All we have to do is study nature and follow her lead on how to revive soil. If we abandon the practice of tilling and chemical applications to our gardens, we can bring back the life that was always meant to be in the soil. Organic gardening has many advantages and while it may be harder to establish in the beginning, it more than pays off with saved time and energy in the long term. After all, the microbes in the soil will take care of your plants. All you need to do is stop killing them!
Do you have any tips regarding how to revive soil that we missed? Let us know!
Originally published in Countryside May/June 2016 and regularly vetted for accuracy.