Soil fertility refers to the ability of soil to sustain agricultural plant growth, i.e. to provide plant habitat and result in sustained and consistent yields of high quality. It also refers to the soil's ability to supply plant/crop nutrients in the right quantities and qualities over a sustained period of time. A fertile soil has the following properties:

The following properties contribute to soil fertility in most situations:

In lands used for agriculture and other human activities, maintenance of soil fertility typically requires the use of soil conservation practices. This is because soil erosion and other forms of soil degradation generally result in a decline in quality with respect to one or more of the aspects indicated above.

Soil fertility and quality of land have been impacted by the effects of colonialism and slavery both in the U.S. and globally. The introduction of harmful land practices such as intensive and non-prescribed burnings and deforestation by colonists created long-lasting negative results to the environment.

Soil fertility and depletion have different origins and consequences in various parts of the world. The intentional creation of dark earth in the Amazon promotes the important relationship between indigenous communities and their land. In African and Middle Eastern regions, humans and the environment are also altered due to soil depletion.

Bioavailable phosphorus (available to soil life) is the element in soil that is most often lacking. Nitrogen and potassium are also needed in substantial amounts. For this reason these three elements are always identified on a commercial fertilizer analysis. For example, a 10-10-15 fertilizer has 10 percent nitrogen, 10 percent available phosphorus (P₂O₅) and 15 percent water-soluble potassium (K₂O). Sulfur is the fourth element that may be identified in a commercial analysis—e.g. 21-0-0-24 which would contain 21% nitrogen and 24% sulfate.

Inorganic fertilizers are generally less expensive and have higher concentrations of nutrients than organic fertilizers. Also, since nitrogen, phosphorus and potassium generally must be in the inorganic forms to be taken up by plants, inorganic fertilizers are generally immediately bioavailable to plants without modification. However, studies suggest that chemical fertilizers have adverse health impacts on humans including the development of chronic disease from the toxins. As for the environment, over-reliance on inorganic fertilizers disrupts the natural nutrient balance in the soil, resulting in lower soil quality, loss of organic matter, and higher chances for erosion in the soil.

Additionally, the water-soluble nitrogen in inorganic fertilizers does not provide for the long-term needs of the plant and creates water pollution. Slow-release fertilizers may reduce leaching loss of nutrients and may make the nutrients that they provide available over a longer period of time.