Fertilizing the yard provides essential nutrients to the lawn and other plants. Before choosing a fertilizer, the gardener must be familiar with the soil's makeup and the plant's specific needs. If the soil is already rich in one nutrient, adding more to the soil may be harmful to some of the plants. When buying fertilizer there is typically a series of three numbers on the packaging. These numbers indicate the percentage of the following nutrients in the fertilizer: nitrogen, phosphorus and potassium.
Nitrogen, a component of organic matter, is represented by the first number in the series. Whatever the weight of the fertilizer, this number will indicate what percentage of the weight is nitrogen, just as the second number indicates what percentage is phosphorus and the last number indicates the percentage of potassium. Of the three, nitrogen is typically the most essential nutrient needed for the lawn and other plants. Nitrogen encourages plant growth. Without nitrogen lawns would not have their deep green color and thick, healthy growth.
Phosphorus, the second number listed in the series, is beneficial to the root system. Phosphorus, which is the next important of the three nutrients, naturally occurs in mineral deposits and rocks. The weathering process releases the nutrient, which is a slow and gradual process. When used in fertilizer the phosphorus is bound by the soil. But, if it is not combined with soil, phosphorus from leaves or grass clippings can become soluble in the street or gutters and can become a source of pollution.
The third number represents potassium, which boosts the plant's immune system. Potassium helps a plant resist disease. Sources of potassium include muriate of potash or potassium chloride. The balance of the fertilizer is comprised of sand or ground limestone and it may have other additives, such as weed killer or micro-nutrients. Even if sufficient amounts of nutrients are added to the soil, if the soil's ph is off, the plants may not be able to absorb the necessary nutrients. It is advisable to take a soil sample to the gardening center or lab to check the ph levels. If they are off, adjustments can be made by amending the soil.