what is compost

Compost is a mix of organic materials that have been decomposed aerobically. Decomposition occurs naturally anywhere plants grow. When a plant dies, its remains are broken down by microorganisms and invertebrates in the soil, and it is decomposed into humus. This is how nutrients are recycled in an ecosystem. This natural decomposition can be encouraged by creating ideal conditions of heat, moisture, and these important organisms present in the compost pile. The microorganisms and invertebrates fundamental to the composting process utilize oxygen and water to decompose the material. The end products of composting are soil-enriching compost, carbon dioxide, water, and heat.

Compost End Uses

Compost is almost universally recommended as a soil amendment. It is principally intended as a blend with soil or other matrices such as coir and peat (although it may also be used to make compost tea). High rates of mixture (e.g. 80–100%) of compost have been occasionally noted in growing media, but generally direct seeding into a compost is not recommended. It is very common to see blends of 20–30% compost used for transplanting seedlings at cotyledon stage or later. The primary factors controlling how well a compost blend performs are salinity and maturity, which singly and together can trigger phytotoxicity symptoms. It is well known that high salt content in growing media will affect water relations of plants, especially in early stages of growth. The effects or symptoms of damage can be yield reduction, leaf deformation and tip-burning or even plant epinasty.

These effects can also be attributed to a variety of other factors that may be present in active or finished composts, depending on ingredients. Such elements include pesticides, presence volatile fatty acids which are by-products of anaerobic conditions or residues of anaerobic digestion, ammonia associated with high manure content, heavy metals such as copper from farm ingredients and sludge, and ethylene oxide from plant debris, any of which can trigger some form of stunting and other phytotoxicity traits. In container-mix studies, it has been demonstrated that immature compost deprives the soil of oxygen content for a significant period of time, resulting in stunting of roots.

As a result of these numerous challenges, the introduction of compost products into professional horticulture as a competition to peat and soil-based products has been significantly less successful than originally hoped for.A Jan 2008 consumer report in the UK severely criticised compost quality, showing that only one out of 24 composts tested against 4 cultivars in actual growing media trials could be recommended as viable "peat-free" product.Nevertheless, the broad popularity of composts and their long term beneficial effects for soils and crops mean that demand will continue to grow worldwide.

Compost ingredients

Given enough time, all biodegradable material will compost, and the primary objective in the modern push to compost is to capture readily degradable materials so they do not enter landfills. However, most small-scale domestic systems will not reach sufficiently high temperatures to kill pathogens and weed seeds or deter vermin, so pet droppings, scraps of meat, and dairy products are often best left to operators of high-rate, thermophilic composting systems. Hobby animal manure (horses, goats), vegetable kitchen and garden waste are nevertheless all excellent raw material for home composting. Early roots of composting as a treatment for municipal solid waste were spurred by awareness of the trash crisis as early as the 1950s, and the rise worldwide of large MSW composting plants in the 1960s into the 1970s was virtually unregulated.Public outcry in Europe against contamination of soils on farms and vineyards from MSW compost containing residues of plastic, metals and glass triggered a shakeup of the industry, and in the 1980s a phasing out of MSW composting.