Understanding Nitrogen Fertilizer

Nitrogen Cycle

• The route that nitrogen follows in and out of soil and plants is called the nitrogen cycle. Climate conditions and soil's biological conditions influence the nitrogen cycle. It is supplied for plant growth from organic matter in the soil, the atmosphere, crop and animal residues, commercial synthetic fertilizer and biological fixation. Plants such as beans and other legumes absorb nitrogen from the air, fix it into their system, and make it available to other plants. Many of sustainable-agriculture companion-planting arrangements are based on nitrogen-fixing plants.

Other Needed Nutrients

• Phosphorus and potassium are the nutrients plants use most after nitrogen. Fertilizer labels list these as N-P-K. Lack of these three nutrients in plants is the biggest growth inhibitor. Other nutrients are needed in trace amounts but are equally important to growth and soil health. They include calcium, magnesium, sulfur, iron, manganese, zinc, copper, boron, molybdenum and chlorine. The complex interaction of these 13 nutrients in soil produces nutrient-rich food. Fertilizer concentrated with only nitrogen, phosphorus and potassium has limited growth benefits.

Manufacturing Process

• Synthetic nitrogen fertilizer is made from factory-produced ammonia. It is often combined with other synthetic nutrients to create compound fertilizers. Ammonia fertilizer produces quick growth effects on plants and has a detrimental long-term effect on the soil, plant and animal ecosystems. The excessive use of synthetic nitrogen fertilizer distorts the natural nitrogen cycle. Rivers in the northeastern United States receive up to 20 times the natural level of nitrogen, and nitrates are the leading source of global air pollution.

Other Sources of Nitrogen

• Natural fertilizers also contain substantial nitrogen to boost plant growth. Bat guano, animal manures, blood meal and fish meal are sources of nitrogen that are used in organic fertilizer. When nitrogen is made available from natural sources, it remains in balance with other nutrients. Microorganisms such as bacteria, fungi, arthropods, worms and other insects convert nitrogen from air into a form that plants can use. In contrast, synthetic nitrogen-laden fertilizer reduces the microorganism populations in soil so that nitrogen is no longer produced naturally.