Fertilizers can be something of a mystery to homeowners. Packages make big claims, but you'd like to know what exactly you're spraying all over your lawn. Lawn fertilizers contain chemical compounds that provide the essential nutrients for a healthy lawn, either alone or in combination. Though products for the homeowner are often sold at a weaker dilution, these chemicals are still potent and should be handled with care and applied according to package directions.
Though lawns require a nice-sized list of essential elements for healthy growth, only three of these--nitrogen (N), phosphorus (P) and potassium (K)--are needed in large amounts. The others are, in general, easily obtained from the air, water or soil without additional help. A complete fertilizer, which contains these three main essential nutrients, is comprised of a chemical mixture: any one of several possible sources for nitrogen, a source of phosphorus such as phosphoric acid and a source of potassium such as soluble potash.
Nitrogen is the most quickly depleted nutrient needed for lawn survival and health, and it is common for homeowners to purchase a nitrogen-containing lawn fertilizer for application. This also solves the common problem of over-applying phosphorus, which can be damaging for nearby water supplies and is often regulated on the statewide level. Common chemical nitrogen sources in lawn fertilizer, according to the Clemson University Extension, include ammonium nitrate, ammonium sulfate, urea and calcium nitrate.
Grasses grow better in soil that is slightly acidic, and the sulfur contained in iron is often used to adjust the soil's pH to a slightly more acidic level. Yellowish grass might be a sign of sulfur deficiency. Lawn fertilizers intended to distribute iron will contain a chemical such as ferrous sulfite, which is insoluble; ferrous sulphate, which is soluble but quickly depleted; or chelated iron, which is wrapped in special chemical agents to protect it from quick depletion and cause it to be released over a longer period of time.