Soil in your garden is divided into what Utah University Cooperative Extension calls "horizons." The surface layer of the horizons is darker, richer and full of organic matter. This 2- to 10-inch layer of soil is called top soil, and is where your plants do the majority of their growing. Chemical and physical properties determine the quality of a topsoil, including texture, pH and drainage. A soil that tests poorly in any of these areas is not worth purchasing and putting into your garden.
Visually inspect the soil for color. The best topsoil, according to Oregon State University, is that which looks dark, is crumbly and smells sweet. Touch the soil and squeeze it in your hand to see if it crumbles.
Add water to the soil to determine its composition. Top soil that sticks together has too much of a clay composition while if it it wet and gritty, it contains too much sand.
Purchase a pH kit from a local garden center or online and test the pH of the soil. According to Utah State University, soil that has a reading of above 7.0 is alkaline, below 7.0 acidic, and 7.0 neutral. Topsoil reading somewhere around the 7.0 range is of good quality, and is adaptable to most plants.
Place a small amount of topsoil in a bowl and add water until it is thin. Preserve a small amount of this water and place it into your pH device's container. Dip the testing strip into the water, or add the chemical included with the pH kit into the water to test the pH. The pH strip, or the water, will change color. This color is checked against a chart and will represent the soil pH.