They are fertilizers that come from animal matter, animal excreta (manure), human excreta, and vegetable matter. (e.g. compost and crop residues). Naturally occurring organic fertilizers include animal wastes from meat processing, peat, manure, slurry, and guano.
In contrast, the majority of fertilizers in commercial farming are extracted from minerals (e.g., phosphate rock) or produced industrially (e.g., ammonia). Organic agriculture, a system of farming, allows for certain fertilizers and amendments and disallows others; that is also distinct from this topic.
These materials include the products of the slaughter of animals. Blood meal, bone meal, hides, hoofs, and horns are typical precursors. Fish meal, and feather meal are other sources.
Chicken litter, which consists of chicken manure with sawdust, is an organic fertilizer that leads to better condition soil for harvest than synthesized fertilizer. In addition to higher yields, researchers valued commercially sold chicken litter at a $17/ton premium (to a total valuation of $78/ton) over the traditional valuations of $61/ton due to value added as a soil conditioner.