Soil structure

The way that the soil particles align themselves or clump together is called soil structure. The best garden soils have a loose, crumblike structure that water, air, and plant roots can penetrate easily. Unstructured soils, such as beach sand, don't clump together, which allows water to flow through them too rapidly for most plant growth. Poorly structured soils, such as heavy clay, clump together so tightly that little water and air can pass through.


Two of the most important goals for organic gardeners are improving and maintaining good soil structure. Improving soil structure can improve water-holding capacity in sandy soils and improve drainage in clay soils.

Many things affect soil structure, but the most important ones from a gardener's point of view include the following:

  • Organic matter: Decayed plants and animals become humus, a substance that helps soil particles bind together into crumblike aggregates. Soils that lack enough humus may clump together too tightly or not at all. Adding organic matter improves the structure of both sandy and clay soils. To find out how to add organic matter, head to Chapter 5.
  • Soil organisms: As they tunnel through the soil, earthworms, beetles, and other organisms open spaces between soil particles, allowing air, water, and roots to pass through easily. Earthworm castings (excrement) are also rich in nutrients. Encourage these beneficial soil organisms by providing food and habitat for them in the form of organic matter.
  • Rotary-tilling: Churning the soil through rotary-tiller blades is a good way to break up compact soils and mix in organic matter. Rotary-tilling (also called rototilling or just tilling) also changes the soil structure.

Although tilling can initially add more air to the soil, be careful not to overtill. Overtilling pulverizes soil aggregates, damages soil life, and promotes too-rapid breakdown and loss of organic matter. Find out more about rototilling in Chapter 5.

✓ Working with wet soil: Avoid walking on, digging in, or rototilling saturated soil. Wet soil, especially clay, packs together tightly when compressed, forming clods that can bake to potterylike hardness in hot sun. Allow garden soil to drain to the dampness of a wrung-out sponge before working in it. Find out about building raised beds to improve drainage and minimize soil compaction in Chapter 5.

Improving and maintaining soil structure is an ongoing process no matter what type of soil you have. Adding organic matter to your soil every year is an important step, particularly for sandy or clay soils. Organic matter acts like a glue to help sandy soils stick together into aggregates that retain the proper amount of moisture. It also helps clay soils drain better by binding with the tiny particles to create larger ones with more pore space. But even healthy, loamy soils benefit from annual additions of organic matter. Organic matter is vital to soil structure, but it also contributes to soil fertility. Head to the later section "Organic matter" for more information.

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Homeowners Guide To Landscaping

Homeowners Guide To Landscaping

How would you like to save a ton of money and increase the value of your home by as much as thirty percent! If your homes landscape is designed properly it will be a source of enjoyment for your entire family, it will enhance your community and add to the resale value of your property. Landscape design involves much more than placing trees, shrubs and other plants on the property. It is an art which deals with conscious arrangement or organization of outdoor space for human satisfaction and enjoyment.

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