Animals in the Soil
by Janet Partlow
It was ten years ago when I lived in the Yakima Valley that I became fascinated with soil. The valley was a splendid place to grow things: life-giving sun for several months of the year as well as high soil temperatures and dry conditions that discouraged slugs made gardening a real joy. I become a fervent convert to gardening: in my little garden patch I double-dug the soil, put in bags of commercial compost, and watered freely. The first year I grew prodigious green potato tops, which produced only a handful of tiny red potatoes. It was then that I started to get the notion that soil is much more complex than we think it is. There are many things that make for good soil - and I didn't have them. During the years in Yakima I developed a fascination for the soil and its helper animals that remains with me to this day.
Healthy soil is a mix of sand, clay and loam. Healthy soil needs organic material: the fall of decomposing leaves, twigs, and dying plants which replace nutrients back into the soil. It needs to have air: compacted soils hold layers of water which drown out plant roots. Soil needs water to keep it spongy, but not so much water that plants die.
Healthy soil also needs animals. There are bacteria and fungi which act as decomposers, taking the organic material and breaking it down into usable form. Some bacteria act as nitrogen fixers, binding nitrogen from the atmosphere for use in the soil. Soil also needs the structures created by fungi, which send out tiny threadlike mycelia to help bind the soil particles together.
Other beneficial soil organisms include nematodes, tiny threadworm-like animals that are predators/parasites on damaging insects such as weevils, borers or root worms. Millipedes like to live near composting material, where they act as decomposers, returning fertility to the soil. Ground beetles are voracious predators on slugs, caterpillars and cutworms and keep our gardens healthy for the plants we wish to encourage.
Moles and gophers also play a very important role in the garden. They dig deep subsurface tunnels, helping to stir up and mix the deeper layers of subsoil and make more nutrients available to the topsoil layer. They also play an important role in aerating the soil, stirring up the soil particles to minimize compaction. As a bonus, they also eat many pest insects, including the non-native slug species that can be so destructive in our gardens.
Finally, there are the earthworms. They eat organic material and leave it in the soil as worm castings, which are high in nitrogen, phosphorus, potassium and micronutrients. In their work, they churn the soil, aerating and stirring it and improving drainage.
Today we improve our Olympia soil by keeping a worm bin. Vegetable leftovers & peelings are put in a wooden box along with a captive colony of red worms. They grind through the weekly food offerings; by the end of 6 months, we have a garbage can full of worm castings to add to the soil.
One of my favorite jobs is to sort through the worm bin. Just last month, on a sunny day, I turned the box out onto a tarp and arranged the contents into cone-shaped piles. As I cleared off the top layers of castings, the worms fled to the bottom of the piles. As the castings sat out in the sun, there arose a rich rotting smell which soon attracted several bluebottle flies. Soon, the Violet-Green Swallows nesting nearby noticed the uproar and started darting over my head, catching the flies. As I sat there, sorting the piles and listening the buzzings of flies and the calls of the swallows, I felt myself to be in a unique and complete ecosystem: from bottom to top, decomposers to producers to predators, all the players were there, dancing with me in a tribute to life.
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