Amendments to Your Soil Constitution

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Robert Dolezal

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Each time you till your garden soil you incorporate large amounts of air into it, fueling a population explosion in the microorganisms it contains. It’s always important to add compost or well-rotted manure whenever you till in order to give these microbes an ample food supply.

Healthy and well-prepared garden soil helps yield healthy produce.

Remember that your garden soil consists of layers that extend from the surface to deep within the earth. The top foot, which is most important to your plants, is the most biologically active layer. Beneath the topsoil is a layer of subsurface soil that, while rich in mineral nutrients, is mostly devoid of life. When you till, it’s important to loosen each layer independently, but avoid mixing them together.

As you work your soil, it’s a good idea to go beyond adding organic matter, especially if it drains too quickly or slowly. A loosening agent, like the mineral gypsum, may help prevent clay particles from sticking together. You may need to add garden lime or sulfur to raise or lower the pH, making your soil more alkaline or acidic. Soils that are too sandy will benefit from having clay and silt added to them, while those that are too heavy will profit from additions of sand.

Garden tillers typically mix the topsoil layer, seldom reaching more than 8-10 inches deep into the earth. To loosen the subsurface layer, it’s necessary to double dig the bed using a shovel. While the process is simple, it requires substantial effort if a large area is to be prepared.

To double dig your beds, start by digging a trench 1 foot deep across the width of your bed. Place the soil from the trench into a wheelbarrow or garden cart, reserving it for later in the process. Next, loosen the soil at the bottom of the trench and remove any rocks or debris, working an additional 9-12 inches deep.

Starting a second trench parallel to the first, turn the topsoil layer into the first trench, filling it with the soil from the second row. Then loosen the subsurface layer found at the bottom of the second trench. Continue in this fashion across the bed until a final trench remains, its subsurface layer turned and loosened. Fill the trench with the topsoil reserved from the first row.

When you’ve finished double digging your entire bed, you can spread your amendments, compost and fertilizer. They should be spread in uniform layers on top of the soil, then mixed into the previously loosened top layer with a shovel, working down the length of the bed at right angles to the original trenches.

You can easily incorporate fertilizers and amendments into your soil by following these simple steps shown in the photographs and described in their captions.

Amending Soil - Step 1

Clear all weeds and plants you plan to remove. Use solar power to kill weeds organically by covering the bed with clear plastic for about 2 weeks before you intend to work the soil.

Amending Soil - Step 2

Dig a trench 9-12 inches deep and one shovel-width wide along an edge of the bed, placing the removed soil on a tarp. Loosen the next 9-12 inches of soil within the trench. Remove all rocks and debris.

Amending Soil - Step 3

Widen the trench a second shovel width, placing the top 9-12 inches of its soil into the first trench. Progress across the area until all the soil has been dug. Fill the last trench with the soil from the first trench (still on the tarp, from Step 2). Use a tiller to thoroughly mix the topsoil.

Amending Soil - Step 4

Cover your area with a 4-inch layer of organic soil amendment, as needed. Add organic fertilizer, as needed, carefully following all package instructions.

Amending Soil - Step 5

Turn the soil amendments into the top 9-12 inches of soil, using a shovel or fork.

Amending Soil - Step 6

Rake the top of the bed smooth. It will be high and fluffy with amendments and air. Water the bed with a sprinkler and allow it to settle for 3-5 days. When the soil firms, your plot is ready to plant.

Tips

Always amend and fertilize your soil before planting.
Most gardeners double dig part of their site in autumn, then do the second part in spring.

Faqs

Q: What’s the difference between amendments and fertilizers, and how do I know what needs to be added to my soil?
A: Most additives improve texture, retain moisture and help with drainage issues. They also help loosen dense soil, correct its acid-alkaline balance and enrich it. Fertilizers add the nutrients that plants (especially vegetables) need to grow. Test your soil first to determine what fertilizers and amendments your bed needs.

Tools

Soil test meters measure pH or nutrient levels (or both soil properties). They make it easy to evaluate your soil and figure out what amendments (if any) need to be incorporated.

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