Soil Structure


It is well worth knowing a bit about soil’s actual composition. Correct analysis of the soil is one of the key elements in the success of growing certain types of plants. The kind of soil you have in your garden—along with other factors such as climate and rainfall—determine which particular plants you can grow.

Since the soil is made up of mineral particles to which organic matter has been added, the nature of a particular soil depends on the nature of the underlying rock. If you live in a river valley—where particles have been ground down to form silt or clay—the soil will have different properties than it would in areas with only a thin covering of soil, where it is probably rocky or sandy. These underlying conditions also determine how acid or alkaline the soil is, another important factor in determining what kind of vegetation it will support.

Improving Soil Structure
Although nature can cope perfectly well with poor soil conditions—ensuring that only suitable plants will survive to propagate themselves—the gardener wants a far wider scope. To grow a larger range of plants than nature had in mind, it is important to improve the soil in various ways.

Clay has the finest particles of minerals and the least amount of air in its structure. Unless you work lots of grit and organic matter into it, it will be hard to grow a good range of plants in clay.

The particles in silt lie somewhere between those of sand and clay soils in size, and if it contains lots of organic matter, silt makes good garden soil. It has a silky feel and is often found in river valleys.

Sand has the coarsest particles of minerals and, although it is well aerated, water runs through it very easily. Sand needs to have plenty of organic matter added to it, to bind the particles and improve its moisture retaining properties.

This is the soil structure for which all gardeners aim: a good combination of organic matter with the basic mineral particles, whether sand, silt or clay. It is achieved by generous and regular applications of composted material.

Plants will not thrive unless they have a certain amount of oxygen for their roots, and heavy clay soil has such small particles that very little air penetrates it. In such circumstances, it is the gardener’s job to create a more porous texture to the soil, normally by adding lots of organic matter, and possibly some grit. Another way of improving heavy clay soil is to add gypsum. If the soil is very heavily waterlogged and fails to drain well, you may consider creating some form of artificial drainage as well.

With light sandy soil, the main problem is that it drains too freely and retains very little moisture. In periods of drought, therefore, plants will suffer and possibly die. Again, the answer is to add plenty of bulky organic matter to help bind the particles together.

To find out what your soil consists of, take a lump of it in your hand and crumble it between your fingers. If the soil is very sandy, you will actually hear the sound of grains rubbing together, and feel them between your fingers. A less sandy soil often found in areas surrounding a river bed is silt, which has a soapy feel to it. Clay is very heavy and sticky with a glaze on its surface that causes it almost to shine.

These are the basic soil types that you will find in your garden. What you have to do is create a loamy soil, a rich mixture of soil that feels light and friable to the touch, and has a pleasant, brown, earthy color to it. This quality of soil encourages earthworm activity and is well aerated— because it is neither too dense nor too crumbly—and holds moisture to the right degree for microbes, mycorrhizae and, most importantly, for plant roots.

Dr. Earth® products contain the right proportions of microbes and mycorrhizae, blended with premium organic materials to help correct and enhance all soil types.