Basics

The most important thing to understand about fertilizer is that they are simply nutrients drawn from nature; nitrogen (N) is taken from the air we breathe, phosphate (P) comes from fossilized sea creatures and potash (K) is found in evaporated sea beds.

Most plants cannot use these nutrients as is, though, so commercial fertilizer companies convert N, P and K ingredients into a form that plants can digest. Plants use these three nutrients in the largest amounts and soil cannot provide enough of them on its own to support a healthy, growing plant. As the plant uses these nutrients and as we harvest our garden, they are taken from the soil. We must replace them or eventually, the soil will not have enough to support any plant growth.

Fertilizer suppliers blend N, P, and K to match the specific needs of farms, fields and crops. When you purchase fertilizer from the store, you'll notice that there are three numbers on the bag. This simply indicates the percentage of nitrogen, phosphorus and potassium in the fertilizer. For example, a bag that reads 20-10-10 contains 20 percent nitrogen, 10 percent phosphorus and 10 percent potassium. Fertilizer manufacturers can make any number of fertilizer analysis for your specific needs.