Compost vs. Humus

Main Difference

The main difference between Compost and Humus is that the Compost is a organic matter that has been decomposed and recycled as a fertilizer and soil amendment and Humus is a any organic matter that has reached a point of stability.

• Compost

  Compost ( or ) is organic matter that has been decomposed in a process called composting. This process recycles various organic materials – otherwise regarded as waste products – and produces a soil conditioner (the compost).

  Compost is rich in nutrients. It is used for example in gardens, landscaping, horticulture, urban agriculture and organic farming. The compost itself is beneficial for the land in many ways, including as a soil conditioner, a fertilizer, addition of vital humus or humic acids, and as a natural pesticide for soil. In ecosystems, compost is useful for erosion control, land and stream reclamation, wetland construction, and as landfill cover (see compost uses).

  At the simplest level, the process of composting requires making a heap of wet organic matter (also called green waste, such as leaves, grass, food scraps) and waiting for the materials to break down into humus after a period of months. However, composting also can take place as a multi-step, closely monitored process with measured inputs of water, air, and carbon- and nitrogen-rich materials. The decomposition process is aided by shredding the plant matter, adding water and ensuring proper aeration by regularly turning the mixture when open piles or “windrows” are used. Earthworms and fungi further break up the material. Bacteria requiring oxygen to function (aerobic bacteria) and fungi manage the chemical process by converting the inputs into heat, carbon dioxide, and ammonium.

• Humus

  In soil science, humus (derived in 1790–1800 from the Latin humus for earth, ground) denominates the fraction of soil organic matter that is amorphous and without the “cellular cake structure characteristic of plants, micro-organisms or animals.” Humus significantly affects the bulk density of soil and contributes to its retention of moisture and nutrients.

  In agriculture, “humus” sometimes also is used to describe mature or natural compost extracted from a woodland or other spontaneous source for use as a soil conditioner. It is also used to describe a topsoil horizon that contains organic matter (humus type, humus form, humus profile).

  Humus is the dark organic matter that forms in soil when dead plant and animal matter decays. Humus has many nutrients that improve the health of soil, nitrogen being the most important. The ratio of carbon to nitrogen (C:N) of humus is 10:1.