Naturally occurring organic fertilizers include (green) manure, slurry, worm castings, peat, seaweed, humic acid, guano, sewage sludge, compost, bloodmeal, bone meal.
Many organic materials serve both as fertilizers and soil conditioners: they feed the soil and the plants. This is one of the most important differences between a chemical approach and an organic approach toward soil care and fertilizing. Soluble chemical fertilizers contain mineral salts that plant roots can absorb quickly. However, they do not provide a food source for soil microorganisms and earthworms. Over time, soils treated only with synthetic chemical fertilizers lose organic matter and the living organisms that help to build a quality soil.
Therefore using organic fertilizers has a positive impact on water pollution, soil erosion and fertility.