Fertilizer sold in the United States is required to have the relative proportions of its active ingredients listed in relation to each other. So-called "10-10-10 fertilizer" consists of 10 percent by weight nitrogen, phosphate and potash.Continue Reading
Nitrogen-phosphate-potash fertilizer is known as mixed, or composite, fertilizer. A 10-10-10 ratio is one of the most popular mixtures, but the relative proportions of each component can be altered for use in various quality soils. Mixed fertilizers are available as 5-10-5 or 5-10-10 compounds, as well as more specialized blends, such as 8-0-24 or 6-6-18. In each case, the first number is the percentage of the total weight made up of nitrogen, which is usually derived from ammonium nitrate or urea nitrogen. Liquid nitrogen is sometimes used for pure, unmixed nitrogenous fertilizers. The middle number is the percentage of the fertilizer made of phosphate, and the third number is the fertilizer's potash percentage.
Together, the three active chemicals used in fertilizer make up less than one-third of the total weight of the fertilizer in the bag. The remaining 70 percent of the fertilizer by weight is usually a bulk filler, such as limestone or sand, that holds the active compounds in place and allows an even broadcasting of the product over soil.Learn more about Agriculture