Organic fertilizers usually contribute some organic matter to the soil. This benefits microorganisms and, in turn, improves soil structure. For best results, always follow label instructions. Organic fertilizers include dried blood, fish or feather meal, rock phosphate, bone meal, seaweed, cottonseed meal and animal manures. Synthetic fertilizers are produced by chemically altering raw materials to convert them into a form readily absorbed by plants.
Synthetic fertilizers are usually very water-soluble and are immediately available to plants.
Examples of synthetic fertilizers include urea, ammonium sulfate, superphosphate, muriate of potash and sulfate of potash.