Fertilizer is any organic or inorganic material of natural or synthetic origin (other than liming materials) that is added to soil to supply one or more plant nutrients essential to the growth of plants. Conservative estimates report 30 to 50% of crop yields are attributed to natural or synthetic commercial fertilizer. (Wikipedia)

              

Commercial Fertilizer:

commercial fertilizers - a substance containing one or more recognized plant nutrients and that is used for its plant nutrient content or that is designated for use or claimed to have value in promoting plant growth. Commercial fertilizers also include lime, gypsum, and manipulated animal and vegetable manures. It does not include unmanipulated animal and vegetable manures, organic waste-derived material, and other products exempted by the department by rule.

Recognized plant nutrients include:

1. Primary nutrients

• Nitrogen
• Phosphorus
• Potassium

2. Secondary nutrients

• Calcium
• Magnesium
• Sulfur

3. Micronutrients

• Boron
• Chlorine
• Cobalt
• Copper
• Iron
• Manganese
• Molybdenum
• Sodium
• Zinc

                                                                                                                        http://agr.wa.gov/pestfert/definitions/commercialfertilizer.aspx

Organic fertilizers are fertilizers derived from animal or vegetable matter. (e.g. compost, manure). ^[1]

Naturally occcuring organic fertilizers include manure, slurry, worm castings, peat, seaweed, humic acid, and guano. Sewage sludge use inorganic agricultural operations in the U.S. has been extremely limited and rare due to USDA prohibition of the practice (due to toxic metal accumulation, among other factors).^[2][3][4]