Organic Fertilizers

Fertilizers derived from vegetable matter, animal matter or human excreta are referred to as organic fertilizers. They are also known as manure or compost, and in contrast to them, the great majority of fertilizers are produced industrially, like ammonia, or extracted from minerals, such as phosphate rock, for example.


The main source of organic fertilizer is peat, an immature precursor to coal. Peat itself offers no nutritional value to the plants, but improves the soil by aeration and absorbing water. Mined powdered limestone, rock phosphate and Chilean saltpeter are inorganic compounds, which can be energetically intensive to harvest.

Animal sources

Animal sources are, essentially, materials which include the products of the slaughter of animals, with typical precursors being bloodmeal, bone meal, hides, hoofs and horns. Chicken litter, which consists of chicken manure mixed with sawdust, is an organic fertilizer that has been shown to better condition soil for harvest than synthesized fertilizer.


Processed organic fertilizers include seaweed extracts, amino acids, humic acid and compost. Other examples are nature enzyme-digested proteins, feather meal and fish meal. Decomposing crop residue (green manure) from prior years is another source of fertility. Researchers at the Agricultural Research Service (ARS) have found that algae used to capture nitrogen and phosphorus runoff from agricultural fields can not only prevent water contamination of these nutrients, but also can be used as an organic fertilizer.

Sewage sludge

Although night soil is a traditional organic fertilizer, the main source of this type is sewage sludge. Animal-sourced urea and urea-formaldehyde from urine are suitable for organic agriculture; however, synthetically produced urea is not.

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