Topsoil is the dirt used in landscaping or gardening to help plants grow. Soil is made up of small particles consisting of air, decomposing organic material, minerals, rock and water. In a perfect world, soil would have a mix of 50 percent solids, 25 percent air, 20 percent liquid and 5 percent organic material. Depending on the need for drainage, root growth or moisture, plants may need one of three types of topsoil. Specific soil needs of individual plants determine the best topsoil to use.
Loam soil is the best type of soil for use when aeration and drainage must be optimized. Loam soils are very tillable and are good for deep-rooted plants. A loam with higher clay content is good for prairie and wildflowers from the Northeast as well as bramble fruits and plants needing moist soil. Loam with a high sand content is preferred for fast drainage needed by herbs, fruit trees and vegetable gardens. Sandy loam holds nutrients, air and water while remaining well-drained. Organic compost and material can be added to replace nutrients absorbed by plants.
Clay soil is made of small, tightly packed particles. Look for lots of water and dissolved minerals in clay soil. Work the soil to avoid compaction. Plant native wildflowers, shrubs and trees in clay soil. Shrub roses and moisture-loving plants do well in this type of soil, too. Adding organic material can separate the small particles to allow more air and root penetration, and increased drainage.
Sandy soil consists of larger solid particles with little organic material. Use sandy soil for fast draining and good air flow. Look for good root growth in this soil. Plants such as Mediterranean herbs, desert plants and root vegetables do well in sandy soil. Trees and shrubs can do well in this soil when fertilized and have applications of mulch.