Fertilizers are organic or inorganic materials that are applied to the soil or the plant to improve its health and provide sufficient mineral nutrient elements.
Plants obtain three of the essential elements they need for growth - carbon, hydrogen and oxygen - from water and the carbon dioxide in the air.
The other essential elements plants need, often classified as mineral nutrient elements, are found in the soil and absorbed by the plant’s root system. The mineral nutrient elements are grouped into two categories, macronutrients and micronutrients, based on how much of each is needed by the plant.
There are three main macronutrients – nitrogen (N), phosphorus (P) and potassium (K).
Nitrogen promotes rapid growth, leaf development, chlorophyll formation and protein synthesis. Phosphorus plays a key role in early root growth, hastens maturity, stimulates blooming and aids seed formation.Potassium increases resistance to drought and disease and also plays a part in root growth as well as in stem development.
You will find the NPK content in the description printed on the front of bags of fertilizer. The description may not expressly say "NPK" (it may simply be implied), but you will at least see a series of three numbers, which correspond, respectively, to the nitrogen, phosphorus and potassium content of the fertilizer. They are always listed in that order.
You’ll find a more detailed breakdown of the fertilizer’s contents on the fertilizer label. The two most important pieces of information here are the guaranteed analysis and the type(s) of nitrogen the fertilizer contains. The type of nitrogen source will be listed, which determines if it is a quick-release or slow-release form of N.
Along with N, P and K, any of the other nutrients contained will be listed on the fertilizer label. The numbers shown for each nutrient give the percentage, by weight, of that nutrient compared to the total contents of the bag.
As with all fertilizer or control products, the label must be read, understood and followed explicitly.
Not all plants have the same nutrient requirements, and you can sometimes do more harm than good when applying chemical fertilizers arbitrarily.
A soil test is recommended to identify the precise needs of your lawn. The soil test will include your soil P and K and other nutrient levels, along with other factors important to the health of your lawn, such as acidity or alkalinity (pH) and Cation Exchange Capacity (CEC). Though soil testing for N levels is possible, such testing is seldom conducted as those levels change quickly.
A soil test also can provide an N, P and K fertilization recommendation based on your turfgrass species.