Digging in to Dirt
How to Create Healthy Soil in a New Vegetable Garden
By Martha Berthelsen
Most gardeners would agree with Michelle Obama's recent comments to her fifth grade garden assistants. "We did a lot of hard work moving that dirt with those shovels. That was harder than I thought it was. Remember we had to get the soil ready? That was hard," she said. Preparing soil for a new vegetable garden can certainly be challenging. However, if you take the time to do it correctly, your garden will surely thank you come harvest time.
To reap the benefits of healthy soil, it is best to understand a few basics. Healthy soil is composed of about 45% minerals from the parent rock, twenty five percent air, twenty five percent water, and two to five percent organic matter, including living organisms. Unhealthy soil has been trampled and compacted when wet, and then baked dry. Or even worse, it's been doused with pesticides. As many gardeners say, "feed the soil to feed the plants."
A magnifying glass will show you that healthy soil is a living ecosystem in its own right. Bacteria, fungi, insects, earthworms, millipedes, and many other creatures feed on decaying plant matter in the soil and on each other. They also break down this organic matter, making nutrients available to plants, and open up pathways for both air and water to penetrate deep underground. Humus, a stable form of organic matter, stays in the soil and improves its ability to absorb and hold water.
Healthy soil does more than just support plants. It absorbs rainfall like a sponge, benefiting creeks by slowing runoff and filtering pollutants. The good news is, no matter what type of soil you have, or its condition, adding organic matter like compost will help. Organic matter improves both heavy clay by improving the texture and porous sandy soils by holding nutrients and water.
There are two ways to add organic matter to soil. The fast yet challenging way is to dig in a generous amount of aged compost with your shovel (use a team of fifth graders if you are so lucky). Before you do so, there is one more important consideration if your soil is mostly clay, as is common in the Bay Area. Digging when the soil is too wet and sticky, or too dry and hard can damage its texture. If you miss that optimum time in spring or fall when the soil's moist but not soggy, water slowly but thoroughly and then let it dry out for a day or two. This simple fix should allow you to dig without gluing your shovel to the ground with mud.
And for that slow and easy method? The answer is mulch, lots of it. Water first if needed, then spread a two to four inch layer of weed-free organic matter over the surface. Then let the earthworms and other critters work the organic matter deeper into the soil for you.
With healthy soil, your plants will develop deep roots and need watering less often. A slow, steady supply of nutrients will lead to strong, disease- and pest-resistant plants. You will be rewarded with a bountiful harvest of healthy vegetables from your own yard to feed yourself, your family, or your community.
