Fertilizer Nutrient Elements
A bag of fertilizer has three numbers prominently featured on the label...something like...5-2-0. It's important to know what those numbers mean because the wrong combination can do more harm than good. The numbers indicates the amount of three major plant nutrients: nitrogen, phosphorus, and potassium, abbreviated NPK.
One way to remember what those things do, and keep them straight is the phrase "up, down, and all around." Nitrogen is needed for green, leafy growth...the up. Phosphorus helps produce healthy roots...the down. Potassium is important for overall plant health and resistance to water or insect stresses, so it's...the all around.
Plants need anywhere from 14 to 18 plant nutrients for best health and production. Magnesium and sulfur comprise the macronutrients along with NPK. The micronutrients include: iron, manganese, boron, zinc, copper, molybdenum, and maybe chlorine. Testing your soil is the way to determine what is needed.