Just like people, plants need nutrients to survive, which they draw up from the ground using their roots. And, just like an all-you-can-eat buffet, your soil will eventually become depleted of nutrients if not restocked. For many decades, chemical fertilizers have provided a convenient solution to soil fertility problems and, applied properly, remain an option for increasing plant yields and vigor. However, gardeners should also know the risks of their use and apply these products judiciously.
Since prehistoric times, people have amended soil to increase its fertility. Ancient farmers used manures, cover crops and crop rotation to replace lost nitrogen in cropland. In the early 20th century, this changed when German scientists discovered a process by which, under intense heat and pressure, inactive atmospheric nitrogen could be converted into ammonia, a source that plants can use. This discovery, called the Haber-Bosch Process, revolutionized agriculture. According to the U.S. Department of Agriculture, not only is commercial fertilizer use seven times higher today than in the 1930s, but the average farmer feeds 10 times the number of people.
Yield increases of this magnitude can't be anything but significant. The so-called Green Revolution of the mid-20th century, powered in part by the yield increases gained from chemical fertilizers, promised to eliminate world hunger, a promise that has not been kept. The impact of chemical fertilizers is felt more keenly in rich nations, who pay less money than ever for food.
Chemical fertilizers differ in the nutrients they provide and the proportion of nutrients. The three major nutrients found in chemical fertilizer are nitrogen--produced by the Haber-Bosch Process--phosphorus and potassium. Other fertilizers may add other nutrients in addition to these. The fertilizer grade is indicated by three numbers that indicate the respective proportion of each nutrient. For example, a bag of 5-10-5 fertilizer contains 5 percent nitrogen, 10 percent phosphorus and 5 percent potassium.
Growing plants constantly deplete the soil of nutrients, and chemical fertilizers are one way to restore soil fertility. Garden supply stores carry fertilizers of varying grades that can be applied in liquid, solid or granular form. Before applying fertilizer, have your soil tested through your local agricultural extension office to determine your soil's needs. The report you receive will recommend a fertilizer grade. Always follow instructions on the package and do not overapply.
Chemical fertilizers carry risks for both your plants and your local ecosystem. Failing to apply them properly could result in damage to your plants. When it comes to fertilizer, more fertilizer does not equal more growth but, in some cases, the exact opposite. Furthermore, improper or overuse of chemical fertilizers can cause pollution of both groundwater and surface waters, such as lakes and streams. Fertilizer pollution accounts for toxins in drinking water and vast aquatic dead zones.