A soil conditioner, also called a soil amendment, is a material added to soil to improve plant growth and health. A conditioner or a combination of conditioners corrects the soil's deficiencies in structure and-or nutrients.
The type of conditioner added depends on the current soil composition, climate, and the type of plant. Some soils lack nutrients necessary for proper plant growth. Some hold too much or too little water, with water conservation aided in the latter. They can be incorporated into the soil or applied to the surface.
Lime is used to make soil less acidic, as is lime-containing crushed stone. Fertilizers, such as manure, anaerobic digestate or compost add depleted plant nutrients. Materials such as peat, diatomaceous earth, clay, vermiculite, hydrogel, and shredded bark will make soil hold more water. Gypsum releases nutrients and improves soil structure. Sometimes a soil inoculant is added for legumes.
Unless clay is incorporated into a healthy crumb structure, water may bond to it too strongly to be available to plant roots or run off before penetrating the surface. Mulching is one technique to correct this.