by Debbie Roland, Compost Specialist
Permian Basin Master Gardener
You stand at the garden center and stare at the bag, potting soil, garden soil, compost. Gardeners have their own lingo. Knowing the difference between soil, dirt, compost and potting soil will give you the edge you need to grow your best yard yet in West Texas.
Dirt is something we sweep out the door. Dirt is debris, something undesirable. As an experienced gardener you will learn to call the substance, we grow plants in soil. Soil is the earth beneath our feet. It’s a mixture of rock broken into small particles and decayed organic matter. It may also contain living organisms, many too small to see, such as bacteria, fungi and larger organisms such as grubs (yuk) and worms (yea).
Soil varies from place to place depending on what rocks were broken down to form it, how fine the rock particles are, and what organic matter has been added to the mixture.
In nature, plants will grow in the type of soil they prefer and each kind of soil has advantages and disadvantages. When we want to grow certain types of plants in areas where the kind of soil isn’t suitable we need to amend it.
Top soil is the layer of soil closest to the surface and that soil generally has more organic matter or humus, therefore it looks darker. Soil isn’t better because it is dark in color. Be careful if you buy topsoil. It could be collected from building sites or waste areas and can be filled with debris, weed seeds, and even dangerous chemicals.
Potting soil really isn’t soil at all because it lacks the broken rocks of real soil. It is usually composed of peat, shredded bark, and vermiculite or perlite. Other products are sometimes used. Fertilizer and minerals are usually added to these mixtures although you must read the bag label to find out.
Plants can grow for a while in soil-less mixtures without fertilizers because plants have the ability to make their own food. But eventually they do need some of the minerals that real soil has and that is furnished with the various plant foods or fertilizers that are on the market.
Compost is organic matter that has decayed to a point where it looks like rich brown crumbles. It may have a few pieces of stem or larger matter still recognizable but most of what went into it should no longer be distinguishable. Compost has nitrogen and a number of micro nutrients plus helpful bacteria and other organisms in it. Plants can be started in compost and it can be used in hanging baskets and pots. Remember it has no broken down rock or minerals in it and those things will have to be added to make compost a good growing mix.
Compost is added to soil in the garden or flower bed to improve it, to add nutrients and micro-organisms, to make it lighter, and hold more water. Compost eventually turns to humus. It would be very hard to add too much compost to any kind of West Texas soil.
Another bagged product on the market is called garden soil. It’s generally a mix of compost, soil from somewhere, and maybe some peat. It is often used to fill raised garden beds. It’s more expensive than amending most garden soils but some people prefer the convenience.
If you are tackling a landscape or gardening project, you may face a confusing selection of product choices. At best, you are making a financial investment; at worst, if you don't know the differences among these products, you may make a costly mistake. So spend some time planning your project and what you will be growing, and choose the best available product for your project.
For more information and help with your questions, you can always call the AgriLife offices in Odessa, 432-3984071, or Midland, 432-686- 4700.