page_title: Uses of compost
section_title: Horticulture
hierarchical_section_title: Uses of compost / Horticulture
caption_attribution_description: English: A comparison of the growth rate of two carob seedlings planted in a compost-sand mix (right) and in sand alone (left). The compost seems to have provided a lot of support for growth. The seedlings were started from seeds at the same time and have been put in the same weather conditions. Note: this is not a fully controlled experiment.
context_page_description: Uses of compost describes the range of beneficial uses for compost. Compost is a versatile product resulting from composting - the biodegradation of organic waste at household, community or citywide level. Composting can be carried out at the household level, in garden composters or in composting toilets, or at municipal level at centralised composting plants. The method of producing the compost has an influence on its possible uses in terms of quantity and quality considerations.
  The basic use of compost is conditioning and fertilizing soil by the addition of humus, nutrients and beneficial soil bacteria, with a wide range of specific applications.
context_section_description: Compost is used in horticulture in a wide range of contexts. In raised bed gardening, compost can be mixed with sand, clay, aged sawdust, and other materials to create an enriched mix for landscape beds or raised-bed gardens.  Compost should be no more than 30 percent of the total mix. Use a high quality mature compost to avoid nutrient and oxygen competition with plants.
  In a container garden, as in bedding mixes, compost may be a beneficial ingredient in potting media, used up to 30 percent of the total mix, depending on salinity and maturity. It is considered a partial substitute for peat moss, but generally lacks the porosity and water-holding capacity of peat so must be used in limited percentages. The nutrient content of compost can also reduce the need for supplemental chemical fertilizers, although this has to be determined in each situation.
  Excavated areas around the foundation of new buildings are backfilled when construction is complete, but these planting zones may contain rubble, residues of toxic chemicals, and other undesirable substances.  Removing the backfill and replacing it with a soil/compost mix will improve soil structure and give foundation plantings a healthier start.
  Two or more inches of compost can be used alone or in conjunction with conventional mulch products to keep root zones cool, conserve moisture, and act as a slow-release fertilizer, provided the product is coarsely textured and mature. For a weed barrier, double or triple the depth of compost can be used, placed on top of a thick layer of newspapers, to replace geomembrane weed barriers. This is obviously only true if the compost is weed free; many are not.
  For trees and shrubs, mixes of well aged compost with the native soils can be used as backfill. Immature composts may cause settling and young root disturbance due to oxygen deprivation. Seasonally, top dress with compost to the drip line and rake into the soil.
  To establish new turf areas (lawns, recreation fields, golf courses), compost can be applied prior to seeding or sodding and work into the soil.  Compost can seasonally be used to top dress and may also be raked into the soil. Some turf farms also use compost, growing grass in a couple of inches of the material to prevent topsoil loss.
caption: A comparison of the growth rate of two carob seedlings planted in a compost-sand mix (right) and in sand alone (left).
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