Material such as plant and animal wastes added to cropland and pastures to improve soil. Provides valuable soil nutrients and increases the organic content of soil (thus increasing moisture content).

Organic fertilizers differ from synthetic fertilizers in both origin and function. Synthetic fertilizers are often derived from petroleum products or from treating minerals with acid to make them more soluble (see phosphate, for example). Organic fertilizers come from naturally available sources; examples include bone meal, manures, greensand, fish emulsion, and compost. Because synthetic fertilizers are highly soluble (and often contain only NPK), they do not generally persist in the soil and provide little or no long term benefits. Organic fertilizers serve the double purpose of providing a wide range of nutrients while also improving soil-structure; in addition, many are slow to release their nutrient load and thus offer ongoing benefit to plants and soil organisms.

Fertilizer made from materials derived from living things, such as manure, bone meal, and blood meal.