Any substance that is applied to land to raise soil fertility and increase plant growth. Fertilizers include natural products such as farmyard manure, guano, and bonemeal, as well as proprietary chemicals. Organic fertilizers tend to have longer lasting effects than inorganic fertilizers but are generally more expensive and slower acting. However they have the advantage of improving soil structure. The three main constituents of fertilizers are usually nitrates, phosphates, and potash (potassium oxide). The relative amounts of these in a compound fertilizer are expressed by the N:P:K ratio. See also compost , macronutrients , micronutrients. |
