Soil Structure – The Foundation for Growing Success

by Sherry Dodson

Whether it is growing vegetables or growing ornamental plants, your garden is an investment in both time and money. The structure of the soil that your plants are growing in is one of the key ingredients in a successful garden, and one that is often overlooked.

Just as the ability to breathe air is vital for our survival, it is also important for the vitality of the plants in your garden. It is necessary for nutrients to be dissolved in water and transported through the soil in order for a plant’s roots to absorb them. Without sufficient air in the soil, plants lose the ability to absorb water and nutrients. If the roots do not have sufficient air to absorb nutrients, adding fertilizer and water to your garden is of little value.

Think of well-structured soil as a well-designed building with ample hallways, living spaces, storage spaces, and doorways where its occupants can move freely without congestion. In soil, these spaces, or pores, are shared by water and air. When soil is saturated with water, gravity causes the water to move fairly quickly through large pores. When the soil is not saturated the forces governing movement of water are cohesion (the attraction of water molecules to each other) and adhesion (the attraction of water molecules to other substances). At this point, the movement of water will be fairly equal in all directions, with gravity having only a slight effect.

Whether your garden consists of clay, silt, sand, or some combination of these three, you can improve your soil’s structure to create an environment that is conducive to healthy root development, resulting in healthy plants. Adding large amounts of organic matter to the soil is the best way to improve your soil structure.

This can be done most easily with the addition of commercially available compost. Adding compost to a clay soil chemically alters the clay and allows aggregates, or clumps of matter, to form, creating airways that allow water and nutrients to flow.

Sandy soils drain freely, but they can allow water and nutrients to flow away too quickly from the plant’s roots. Adding composted material to sandy soil also creates clumps of material which improve the water-holding capacity of the soil.

You can work compost into the top layer of your soil, or it can be added as a mulch, which allows earthworms to eat and disperse the compost throughout the soil. Add about a 3” layer, being careful to keep the compost away from the plant’s main stem. This should be done annually to enhance your soil’s structure.

Just like a well-designed building, well-structured soil will enhance your garden’s growth and your enjoyment of it.