Good potting soil provides your container-grown plants with the medium they need to establish a strong and healthy root network. Instead of buying potting soil in a garden store, save yourself money by mixing your own potting medium. The best homemade potting soil has the perfect mix of loam, organic matter and sand for optimal moisture retention and drainage.
Pour a gallon of standard garden topsoil into a baking pan, making the soil 3 to 4 inches deep. If your pan isn't large enough, use several pans.
Sprinkle the dirt with water to moisten it evenly, but not so wet that it forms a puddle in the pan.
Bake the soil in your kitchen oven at 180 degrees Fahrenheit for 1/2 hour. This effectively sterilizes the topsoil and kills any soil-borne pests and diseases, according to North Dakota State University.
Mix the soil with a gallon of sphagnum peat moss. This helps increase the soil's ability to hold moisture and nutrients.
Add 1/2 to one gallon of coarse sand, depending on how sandy or clayey your original garden topsoil was, to adjust the finished soil's drainage and consistency. Test the soil texture by grabbing a handful of soil and releasing it. The soil texture should be loose enough that it crumbles slightly when released but still retains a mound-like shape, and not so sandy that it falls into fine particles.