The problems with over fertilizing

Landscaping and lawn care is a big business. There are around 25 to 30 million acres of turf and lawn in the United States. When compared to major agricultural crops, turfgrass ranks fifth in terms of acres. Statistical ranking by area in acres is corn, soybeans, wheat, hay and turfgrass.

A typical recommended homeowner fertilization program consists of one pound of Nitrogen per 1000 square feet three to four times a year. This translates into 160 pounds per acre each year that a homeowner applies to their lawn. Multiplied by 25 million acres of grass in the US, it equals about two million tons of Nitrogen fertilizer every year. When it is put into these terms, it is easy to understand how homeowners can contribute to the pollution of the environment.

Taking a soil test and understanding fertilizer ratios will help reduce over application of fertilizer. Once you have over-applied fertilizer, the only thing you can do to reduce amounts is wait.

Nitrogen- is required in soils to promote top growth in plants (the green part). Nitrogen is used by plants any time they are actively growing. If you have excess Nitrogen in your soil, your plants will need time to use it up. There is no magic chemical to neutralize nitrogen.

A perfect example of too much Nitrogen in the soil is seven-feet tall tomato plants that never bear fruit. Gardeners commonly apply more fertilizer thinking that is the problem, when actually they are making it worse.

Phosphorus and Potassium- need to only be applied according to soil test results because phosphorous and potassium are rarely deficient. Once they reach a sufficient level, they stay in the soil for a long period of time. Excessive amounts are frequently caused by the repetitive application of a complete fertilizer. A complete fertilizer consists of all three nutrients, Nitrogen, Phosphorous and Potassium, and will be expressed in a ratio such as 10-20-10, or 17-18-19.

When purchasing fertilizer, you will notice, there are three numbers that identify the concentration, for example 10-20-10. These three numbers represent percent Nitrogen, Phosphoric Acid, and Potash in that order. Phosphoric acid is the source of Phosphorus, and Potash is the source of Potassium. So a bag of fertilizer that is labeled 10-20-10 is 10% Nitrogen, 20% Phosphoric Acid, and 10% Potash.

The reason industries make so many different kinds of fertilizer is because it should be applied on a need-only basis. In most cases, a Nitrogen-only fertilizer is needed, such as 46-0-0, or 34-0-0.

The only way to know what amounts of fertilizer exist in your soil is to do a soil test.

Date: 11/20/06

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