Clay soils often drain slowly. Compost will benefit almost all soils, improving the water-holding capacity and nutrient retention of sandy soil and improving the drainage of clay soil. Although the quantities of nutrients in compost tend to be rather low, the nutrients are in organic forms that make them more stable, slowly releasing the nutrients over time for uptake by plant roots. Humic acid in compost also makes other nutrients in our alkaline soils more available for plant uptake. Till compost into the soil to a depth of 6 to 8 inches for good distribution throughout the root zone.
Municipal composts made from shredded woody landscape wastes tend to behave like natural fungicides.
In experiments we've conducted in the field and in the greenhouse, a biosolid compost from the City of Albuquerque was found to suppress seedling diseases in chile and snapdragons. Compost also can be used as mulch around vegetables and in flower beds.