The law requires that fertilizer labels inform the consumer of the minimum guaranteed contents of the product. Information on labels is fairly standardized. Manufacturers give the percentages of nitrogen, phosphate, and potash, and the sources of the nutrients. Some manufacturers also include secondary nutrients (calcium, magnesium, and sulfur) or minor nutrients in their fertilizers, which may or may not be listed. The brand name of the product is listed first, followed by the formula or analysis of the fertilizer. The analysis always gives the percentages of nitrogen, phosphate, and potash that the fertilizer contains, listed in that order. For example, a fertilizer with an analysis of 8-12-4 contains 8 percent nitrogen, 12 percent phosphate, and 4 percent potash. The guaranteed analysis is the manufacturer's warranty of the minimum nutrient content of the fertilizer. The analysis may also list some secondary nutrients or minor nutrients. The source of the primary nutrients--the chemicals from which they were derived--is stated next. The derivation determines their availability to plants. Some fertilizers have an acid reaction in the soil. If this potential exists, the label will indicate the number of pounds of lime it would take to neutralize the acidity of the fertilizer once it is in the soil. Other fertilizers have an alkaline reaction in the soil. If this potential exists, the label will indicate the degree to which the fertilizer will add to the alkalinity of the soil; this is stated in equivalent pounds of lime. On the labels of some specialty fertilizers, the words chelating agent appear. A chelating agent is a substance that is added to fertilizers containing nutrients derived from metals.
Related Links
Minor Nutrients
Nitrogen
Phosphorus
Potassium
