Vegetable Soil Types

Posted on 21 March 2011

You’ll need to understand a few fundamentals about soil before you start to plant. In garden soil, air, water, solar energy, bacteria, fungi, humus (decaying organic material), and a host of small organisms (such as earthworms) interact with soil particles to produce a good environment, encouraging seeds to sprout and roots to grow. At the same time, many factors can disrupt this balance. Most soil problems stem from poor physical conditions. Compaction is the most troublesome. Soil compaction can restrict free entry of air, penetration and drainage of water, and activity of all soil organisms. Breaking up compacted soil is the first step in counteracting this condition; adding soil amendments keeps the soil from becoming compacted again. Before you prepare your soil for seeds and plants, you should try to identify the type of soil you have and learn how to improve it.

There are roughly four different types of garden soil, based on differences in structure and texture: clay, sand and gravel, silt, and loam. A fifth type, organic soil, is less common around homesites. The descriptions that follow will help you identify your soil type.
1.Clay soils
Clay soil, composed of many small, flat particles, feels sticky or plastic in your hands. Clay comes in many colors: red, yellow, bluish gray, or almost black. Clay soils warm up and dry out slowly, take in water slowly, and can store reserves of nutrients better than most other soils.
Clay can become as hard as a rock duting dry, warm weather if not watered regularly. Once dried out, it is almost impossible to water clay soil adequately with sprinklers. The surface seals over and stops water from penetrating easily. If this happens, you should make irrigation furrows to hold the water until it can soak in. Improve clay soils by digging in generous amounts of organic matter, such as peat moss, compost, or well- rotted manure, to improve drainage and aeration. Gypsum also helps improve the texture of clay, but does not add nutrients to the soil. Adding only sand to clay will not improve it; the soil will continue to form crusts
2.Sand and gravel soils
If your soil looks and feels like a sandbox or gravel pit, you have sandy or gravelly soil. Sandy soil is easy to work and warms up rapidly. However, it dries out quickly and then may blow around. In direct sun it can reflect enough heat to damage a vegetable crop. Fortunately, most sandy soils contain enough clay particles to make them reasonably responsive to fertilizers. Pure sand contains almost no nutrients and has little capacity to store moisture. However, most sandy soils have enough clay particles to hold some nutrients.
Gravelly soils are usually a mixture of gravel and sand, silt, or clay. Generally low in organic matter, they are also low in natural fertility. The best way to improve sandy or gravelly soil is to remove the larger pebbles and stones; then add coarse organic matter, such as peat moss, compost, or well-rotted manure. Clay added to sandy or gravelly soils will tend to collect in impervious layers instead of improving the soil.
3.Silt soils
Silt has an intermediate size between clay and sand. It consists of small, gritty particles that can pack down very hard. Silt ranges in color from gray to tan, yellow, and red. It’s usually not very fertile. Silt topsoils are often found over dense layers of clay that slow or stop drainage.
Both the topsoil and these lower layers should be broken up and kept loose by adding copious amounts of peat moss, compost, well-rotted sawdust, or wood shavings. Adding organic matter will improve the structure and fertility of silt soils. Adding clay or sand will not improve silt.
Loam contains various proportions of clay, silt, sand, and organic matter. The proportions of each determine how easy the soil is to cultivate and how productive it is. Sandy loam with a fairly high content of organic matter is the easiest to cultivate, water, and weed. A loam that contains more than one-third clay acts almost like solid clay and needs lots of added organic matter to make it easy to manage.
5.Organic soils
Dark in color, organic soils are composed largely of peat moss or leaf mold. Your soil is not likely to be organic unless your house is built on an old lakebed, bog, or forest site. Organic soils are easy to work, weed, and water, but may warm up slowly because they retain moisture.
Since organic soils are usually high in nitrogen, they can benefit from fertilizers high in phosphate and potassium. Micronutrient deficiencies (of iron, copper, cobalt, zinc, and manganese) are common in this kind of soil, especially in the Southeast, but can be remedied by using special fertilizers containing the missing nutrients.

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