The composition of soil is determined by the amount of sand, clay or silt it contains. Clay soils retain moisture, drains slowly, compacts and warms from the sun very slowly. Soil texture can be tested by hand; if you hold a clump of soil by hand and it doesn't crumble, this soil is clay. A more reliable test can be performed at home and while the test takes several days, it is simple and accurate. All soil will most likely contain some clay, but the key is finding how much clay your soil contains.
Take soil samples from four different areas of a dry garden, place in bucket and mix together.
Place two inches of soil into a liter jar.
Fill the jar two-thirds full of water.
Add one tsp. of dish detergent or salt to the jar.
Shake the jar for one minute, place jar on flat surface and wait for soil to settle.
Measure the layers with a ruler, documenting each number to determine percentages after the test is finished.
Measure the sand after a minute; sand particles are the heaviest and settle the quickest.
Measure the silt after two hours when it will be settled. Silt is darker than sand.
Measure the clay layer after one to two days. Clay settles at the top, is fine textured and lighter in color.
Measure the total amount of soil once it has settled. Divide the amount of each layer by the total amount of soil to determine percentage of each layer.