Compost is often called black gold and many consider it the most important form of organic matter. It is universally recognized for improving soil structure and water-holding capacity. Compost helps the soil stay loose and easy to cultivate.
Compost is, in fact, the end-product of the decomposition of organic matter. Making and using compost is also a way to recycle organic matter, especially materials that might otherwise have been treated as home or industrial wastes.
In addition to soil improvement and the economic and social benefits of recycling organic matter, composting can provide other benefits. Composts help fight soilborne pathogens that cause plant diseases. However, not all composts are suppressive to all diseases.
Compost, along with other organic matter, improves the capacity of soil to hold nutrients through a complex process called cation exchange capacity. In addition, compost indirectly provides nutrients for plant use when earthworms and other organisms digest the organic matter, producing nutrient-rich castings, or excrement.
These products are significantly richer in nutrients than the surrounding soil, and in a form, which is readily available to plant roots. While compost provides small amounts of nutrients and makes other nutrients more available, it is not considered fertilizer. However, in many organic gardening or farming systems, compost is the major amendment to enrich soil.
Not all composts are alike. Composts vary greatly, depending upon what goes into them and how they are processed. Quality also varies depending on maturity, pH, presence of weed seeds, concentration of toxic substances, and the population of soil-dwelling organisms, such as earthworms, insects and microorganisms.
The term “compost” is not regulated, so a wide range of products can be marketed under that name. Higher quality compost is not too wet, is mature and has good water-holding capacity and nutrient availability.