• Nitrogen fertilizer is frequently used for multiple plant varieties.Hemera Technologies/Photos.com/Getty Images
  
  Plants need food just like animals do. If the environment is not providing the nutrients that a plant needs, fertilizer can be added to the soil to keep the plant growing healthily. Fertilizer can be made of several different components but both nitrogen and phosphorous are common and assist greatly in plant growth. Nitrogen fertilizer has several common effects on plants.
  
  

Faster Growth

• Plants can only grow if they have nutrients handy to give them the energy needed to support cell division and other processes. Fewer nutrients means the plant needs to pace itself in regards to self-sustainment. As a result, the plant grows more slowly or not at all. Adding nitrogen to the soil provides a surplus of food at the plant's disposal that allows it to support more biological processes at an accelerated rate. As a result, the nitrogen allows the plant to grow much faster than it might otherwise without the nitrogen introduced.
  
  

Improved Crop Yield

• Nitrogen fertilizer also assists in plants growing fruits and vegetables that are more robust and that can be used for consumption, though concerns have been raised regarding the risks of eating foods that have been enhanced through chemical means. Plants use nitrogen in the creation of proteins and nucleic acids, which are then used for the construction of leaves, fruits and other structures. The nitrogen can then help the plant produce larger crops because of the increase in the nitrogen available for creating these structures.
  
  

Excessive Algae Growth

• Arcadia Bio-Sciences report that plants typically use less than one-half of the nitrogen fertilizer put into the soil. The remaining supply typically drifts through the soil before running off into water supplies. The nitrogen then acts as a nutrient for algae, which are simple water plants. The algae population feeds and then spreads due to the nitrogen exposure until the nitrogen runs out and the algae reduces the oxygen level in the water, killing off not only the algae itself but also fish and other life forms. This can result in "dead zones" where entire ecosystems are destroyed for large stretches of water due to the introduction of nitrogen fertilizer.