All living things need nourishment and, for plants, this nourishment comes from the soil. Not all soil is equal, however, nor do plants need just one type of soil. There are four basic soil types: clay, sand, silt and loam. One of the first steps in planning a garden is determining what type of soil is in the garden. From that point, adding organic matter improves the quality of the soil.
Test your soil by taking samples to the local agriculture extension agency; it can also be tested at home by using one of two tests. The jar method takes several days, according to the University of Minnesota, but provides visual results. Pour 2 inches of soil into a 1-liter jar. Add water to fill the jar two thirds full and pour in 1 tsp. table salt or liquid dish detergent. Shake the jar to mix the contents. Place the jar on a level surface. After 1 minute, measure the depth of sand that has settled to the bottom. Two hours later, measure the layer of silt. Two days later, measure the clay.
Squeezing the soil gives an immediate, but more general, result. Take a handful of lightly moist soil, squeeze it between the palms of your hands and then tap it. If it forms a sticky ball that doesn't fall apart when tapped, it is clay. If it forms a soft ball that crumbles easily when tapped, it is loam. If it does not form a ball and runs through your hands, it is sandy.
Clay soil is composed of tiny particles that easily compact together. It retains nutrients but is hard to dig. Compacted clay soil creates two problems. Water does not drain easily through it, which can lead to root rot in some plants. When it is dry--as in periods of drought--clay soil gets hard and looks like cracked pottery.
Amend clay soil by mixing in equal amounts of sand, compost, peat moss, rotting leaves or manure. Adding garden gypsum (hydrated calcium sulfate) to clay will loosen up the compacted particles; however, it might increase the soil's acidity.
Sandy soil is composed of tiny pieces of minerals that are bulkier than clay particles. It is light and loose, feels gritty and drains easily. This rapid drainage leaves the soil dry and might wash the nutrients away from the roots of the plants.
Sandy soil can be amended by mixing in 2 inches of compost, manure or rotted leaves to the top 6 to 12 inches of garden soil.
Silt particles are between the size of sandy and clay particles. Silty soil breaks easily when it's dry and has the appearance of flour, according to Cornell University. Moist silt feels slippery. This type of soil does not dry out as quickly as sand and retains the nutrients.
Loamy soil is a mix of sand, clay and silt. "The ideal loam soil contains 40 percent silt, 20 percent clay and 40 percent sand and organic matter," according to the University of Minnesota. Loam is dark, nutrient-rich soil that retains moisture and provides an optimum growing condition for most garden plants.