To grow, plants need sixteen essential nutrients. Carbon, oxygen and hydrogen are absorbed from the air and water, the other nutrients come from the soil. Most of the nutrients are only used in small amounts and available to plants from the natural breakdown of organic material and mineral components in soil. Synthetic or organic fertilizers are used to improve the fertility of the soil.
The nutrients from the soil that are most important for plants are nitrogen, phosphate and potassium. The percentage of these three nutrients are always listed on a fertilizer, usually as a three number code (10-25-15 for example means that the fertilizer contains 10% nitrogen, 25% phosphate and 15% potassium).
Synthetic fertilizers are the most-used fertilizers, because they are easy to use, inexpensive and easily absorbed by plants.
The problem with synthetic fertilizers is that the excess of nutrients leach into the water causing contamination and endangering the fish and amphibians. A large percentage of our rivers and lakes are polluted because of agricultural runoff. Another problem with synthetic fertilizers is that they only feed the plants, not the soil. This causes a gradual decrease in organic matter in the soil. Once the organic matter is used up, the soil will become compacted. A lack of organic matter also leads to a reduction in soil organisms, making it more susceptible to insect or disease infestations. Many commercial fertilizers also contain toxic metals, including arsenic, mercury, lead, dioxin, chromium and cadmium.
Synthetic Nitrogen Fertilizers
The overuse of synthetic nitrogen fertilizers causes environmental problems like air and water pollution and health problems like respiratory ailments, heart disease and cancer. Most crops grown in industrialized countries receive more nitrogen than they can use. This has a dramatic effect on the global nitrogen cycle.
Nitrogen is a vital element essential to living ecosystems. It is the primary nutrient for all green plants. When excessive nitrates leach into the water however, it can greatly affect our ecosystem. High concentrations of plant nutrients causes large algal blooms to grow. These algal blooms consume a lot of oxygen and block the sunlight, causing other organisms to die. Regions of water with low concentrations of oxygen are called 'hypoxia regions', often referred to as 'dead zones'. Examples of hypoxia regions can be found in the Gulf of Mexico, the Mississippi River and the Black Sea.
Heavy applications of nitrate fertilizers also allow nitrates to accumulate in vegetables, causing health risks to the consumers. Nitrates in drinking water have been associated with an increased risk of bladder cancer.
For more information, please check out the Sources and Resources page.
Copyright © 2004 by Wanda Embar. All Rights