Fertilizers come in a dizzying array of formulations. Walk through the garden center at the local warehouse joint, and you´ll be confronted with dozens of different products, each touting itself as the cat´s meow for your lawn. You can cut through the hype and get the right stuff though, if you know what you´re looking for.
Fertilizers can be divided into 5 categories: Growth, starter, balanced, complete and special need. These are categorized based on the amounts of Nitrogen, Phosphorous and Potassium in the bag, or the N-P-K ratio.
A growth fertilizer will have a high N content and relatively low P and K content. Ammonium nitrate is the highest Nitrogen fertilizer you can buy, and it is potent stuff. It is usually rated as 33-0-0 or 34-0-0. The bag contains 33% or 34% Nitrogen and the other 66% or 67% is inert material. Other formulations of growth fertilizers will contain 5, 6 or even 7 times more Nitrogen than anything else. Use growth fertilizers very sparingly, applying them lightly during the peak growing season of your grass.
A starter fertilizer is used to help a new lawn become established. They contain very small amounts of Nitrogen relative to the other two nutrients, and you will often see them in a 5-20-20 formulation. New lawns need extra Phosphorous and Potassium to develop strong roots and resist disease, but they also need a tad of Nitrogen for growth. Use these fertilizers as recommended on your seed package, or as recommended in a soil analysis conducted prior to planting.
Balanced fertilizers are just what they sound like--the amount of nutrients contained in the bag are balanced. You will see these as 6-6-6, 8-8-8, 10-10-10, etc. Unless a soil analysis has shown that your soil is deficient in all three nutrients, your lawn will rarely need a balanced fertilizer. These are better suited towards other plants in your landscape, such as trees, shrubs, annuals, perennials and vegetables.
Complete fertilizers have 3 or 4 times as much Nitrogen as Phosphorous and 2 times as much Nitrogen as Potassium. In most cases, this is the stuff your lawn will use best. They are called "complete" because they provide nutrients in a mix that completely satisfies most grass´ requirements. If you only make one or two fertilizer applications a year, this is the stuff you want.
Special need fertilizers are formulated for the requirements of specific grass types, such as Centipede, or to correct a soil deficiency problem. 15-0-15 is the only fertilizer you should use on Centipede. 0-0-60 is used to correct severe Potassium deficiencies, and 0-40-0 is used to correct phosphate poor soil. Unless you have Centipede, you should have your soil analyzed by the extension service in your county before buying and using a special need fertilizer.
