A soil amendment is any material added to a soil to improve its physical properties, such as water retention, permeability, water infiltration, drainage, aeration and structure. The goal is to provide a better environment for roots. To do its work, an amendment must be thoroughly mixed into the soil.
On clay soils, soil amendments improve the soil aggregation, increase porosity and permeability, and improve aeration, drainage, and rooting depth.
On sandy soils, soil amendments increase the water and nutrient holding capacity. There are two broad categories of soil amendments: organic and inorganic. Organic amendments include compost, manure, peat moss, wood chips and sawdust. Inorganic amendments include pumice and lava, vermiculite, perlite, pea gravel and river sand.
