A whole universe exists in a mere teaspoon of healthy soil. From microscopic bacteria and fungi to a variety of worms, arthropods, and other insects, the interplay of organisms beneath our feet is a perfectly choreographed dance, and each member has a vital part to play. Healthy soil is living soil. It is soil in which living things live, breed, eat, defecate, and die. The problem with pesticide, insecticides, and other -cides, in general, is that they wipe out several if not all of these vital players.
From the microscopic to the commonly seen and little appreciated, here are some key organisms you want in your garden soil.
We're so used to waging war on bacteria (note the anti-bacterial everything in the cleaning aisle of most grocery stores) that we often fail to understand that there are many good, useful, necessary bacteria. In soil, bacteria are necessary for decomposing plant matter and releasing its nutritive value into the soil, where it can be used by plants and other soil-dwelling organisms. Perhaps most amazingly, bacteria are able break down not only organic matter, such as plants and animals, but chemical pesticides as well.
[u]Did You Know?:[/u] If all the bacteria on a single acre of soil were weighed, they would weigh approximately 1.2 metric tons!
Though we typically associate algae with ponds, streams, and other moist environs, algae are actually very important to healthy garden soil. Even desert soils contain algae. Algae is a key player in building soil -- how amazing is that? Like all plants, algae are able to photosynthesize, turning the sun's energy into carbon dioxide. When algae gives off carbon dioxide, the CO2 combines with water, which makes carbonic acid. Carbonic acid is able to break down rock and stone -- resulting in soil.
[u]Did You Know?:[/u] In one gram of soil, it's possible to find up to 100 million algae.
Like bacteria, we've come to see fungus as a bad thing. But in your soil, fungi has a vital role to play. Fungi are the main recyclers of nutrients for both plants and other soil organisms. Some fungi form mycorrhizal relationships with plant roots, which work to the advantage of both the plant and the fungi. Others work in tandem with soil-dwelling arthropods such as millipedes. Some eat harmful nematodes and insects before they're able to start feeding on a plant's roots. Fungi collonize fallen plant debris and quickly help it decompose. Without fungi, decomposition (both within the soil and in your compost pile) would not happen. [u]Did You Know?:[/u] By some measures, fungi are some of the largest and oldest life forms on Earth. A single fungi occupying over 1,500 acres was discovered in 1993 in the Pacific Northwest. It is estimated to be somewhere between 1,000 and 10,000 years old. 4. Slime Molds The first time you come across the aptly-named Dog Vomit slime mold in your garden, you're first instinct will be to try to eradicate it. It is ugly, and gross, and you'll be sure that something that ugly can't possibly be good for your garden. But be assured that slime molds are a common member of a healthy soil community. Slime molds help break down leaves and dead wood. If you'd rather not look at them, you can simply dig them into the soil. [u]Did You Know?:[/u] There are nearly 800 species of slime molds. 5. Earthworms It's a good rule of thumb that the more earthworms you have in your garden soil, the healthier it is. Earthworms tunnel through soil, which aerates it and supplies plant roots and soil dwelling organisms with oxygen. This tunneling loosens the soil, which makes it easier for plants to grow and improves drainage. In addition, they produce nutrient-filled castings as they work, which improves soil fertility. [u]Did You Know?:[/u] Earthworms can tunnel as deep as 10 feet into the soil. 6. Mites Mites are creatures that also tend to get a bad rap, but they are definitely allies in your quest for healthy garden soil. They start munching on dead leaves and other plant matter, which allows soil bacteria to come in and finish the job and release nutrients into the soil. Springtails, which are also arthropods and closely related to mites, do much of the same work. [u]Did You Know?:[/u] In one square meter of soil, you're likely to find anywhere between 100,000 and 400,000 mites. 7. Millipedes and Centipedes While many of us cringe at the sight of one of these guys in our homes, you definitely want them in your garden soil. They eat decaying organic matter, which helps it break down so soil bacteria can use it. They also eat fungi and algae. Millipedes tend to focus more on eating plant matter, but soil centipedes are meat eaters, and hunt down smaller insects in the soil. Both produce numerous droppings which improve the texture and fertility of your soil. [u]Did You Know?:[/u] Millipedes protect themselves from other insects, mammals, and birds by secreting a toxic substance on their backs. Centipedes have spider-like spinnerets, which release a sticky, stringy substance to protect themselves from predators. 8. Spiders Spiders are an important part of the soil ecosystem. They are predators that help keep the populations of insects and soil arthropods (which, while beneficial, would cause damage if left to run amok) in check. While most of us think of the spider spinning its web, almost all species of spiders dig into the ground in addition to spinning webs. They hunt insects in the soil, and burrow to protect themselves from the elements. [u]Did You Know?:[/u] Anywhere from 100 to 150 spiders live in a square meter of soil. This helps keep other insect populations in check. 9. Wood Lice Many kids know these gray, armored arthropods as "roly-polies" due to their ability to roll themselves into a ball to protect themselves from harm. They are also important decomposers and scavengers in garden soil, helping to break down the remains of plants and animals so soil bacteria can come along and convert the remains into soil nutrients. They are one of the few arthropods that really thrive in dry soils, due to their ability to convert their own urine to water. [u]Did You Know?:[/u] Wood Lice have retained gills from their prehistoric, water-dwelling days, and use these gills to survive in very moist conditions. This, along with their ability to make their own water, allows wood lice to thrive in both wet and dry conditions. 10. Ground Beetles There are over 30,000 species of ground beetles. These predators are responsible for keeping insect populations in check, usually along the surface of the soil and under leaf litter. Some ground beetles tunnel into the soil in search of prey. Studies done in Britain have shown how vital ground beetles are, and how susceptible the beetles are to pesticides. Scientists tested the effectiveness of spraying an insecticide on one cabbage field to protect it from cabbage root maggot, and leaving an adjacent field unsprayed. When it was over, they found MORE maggots in the field that had been sprayed. Why? Because the pesticide killed off many of the ground beetles that would have kept the maggots in check. [u]Did You Know?:[/u] A ground beetle can eat two and a half times its own weight in food every day. These ten wonderful organisms barely scratch the surface of life in our soil, and scientists are discovering more all the time. Our soil is alive; a whole world exists beneath our feet. We can help these creatures do what they do best by eliminating our use of pesticides and chemical fertilizers, reducing activities (such as rototilling) that disturb the soil, and using nature-friendly gardening practices such as permaculture and mulching. In return, they'll make soil. Sounds like a fair trade to us.