Nitrogen is one of three primary macronutrients plants require to grow, and most synthetic and organic fertilizers contain it. While it is essential for healthy crops and gardens, and using nitrogen fertilizers can provide benefits for your plants, the misuse of nitrogen fertilizers can have devastating consequences for your garden and the local ecosystem.
Nitrogen is essential for many life processes, including metabolic processes involving energy and the construction of enzymes and proteins. Plants deficient in nitrogen weaken and develop chlorosis, a disease in which the leaves turn yellow due to a lack of chlorophyll, the green pigment in leaves required for photosynthesis. Plants without adequate chlorophyll cannot produce the energy that they need to stay alive. Adequate nitrogen made available through fertilizer applications may prevent and correct these problems.
Overuse of nitrogen fertilizers may damage plants. Nitrogen fertilizers may release ammonia and salt into the soil that leaches water from the plant, causing it to appear burned. Excessive nitrogen can also weaken plants, increase susceptibility to pests and affect the taste of food crops.
Some plants accumulate nitrates in their tissues that may reach toxic levels for young children and livestock. According to the University of Georgia Cooperative Extension, applying nitrogen fertilizer increases the risk of nitrate accumulation that may reach toxic levels. Plants are especially at risk for high nitrate levels during periods of low photosynthesis, such as drought or extended cloudy periods, immediately after a rainfall and when plants are young. Maintaining healthy growing conditions for plants and using nitrogen fertilizers judiciously reduces the risk of nitrate accumulation.
Aquatic Dead Zones
Around the world, aquatic ecosystems once teeming with plant, animal and microbial life have been reduced to dead zones by overgrowth of algae that draws all available oxygen from the water. According to North Carolina State University's College of Agriculture and Life Sciences, one of the largest dead zones lies at the mouth of the Mississippi and is roughly the size of the state of New Jersey. Dead zones are caused, in part, when excessive nitrogen fertilizers run off from the land and into the water. The same effects on plant growth that nitrogen exerts on land plants affects algae as well, and the resulting spike in algae growth chokes out all other life.
Drinking Water Pollution
The West Virginia University Extension Service reports that high nitrate levels are the number one reason why public water supplies are closed for safe drinking water violations. Normal amounts of nitrates from nitrogen fertilizer dissolve as water leaches into the ground. When nitrogen fertilizer is over-applied, however, more nitrates become available than can be dissolved, and pollution of groundwater results. When groundwater sources connect to rivers and streams, surface water pollution also occurs.