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For those that are interested I have written a simple explanation of the Nitrogen Cycle--where fertilizer comes from and where it goes. I will be glad to answer any questions.


Nitrogen Cycle

Nitrogen is very common in our atmosphere, approximately 80%, but that nitrogen is not available to plants. Plants use what is called fixed nitrogen (various forms of fertilizer), nitrogen in the chemical forms of nitrate (NO3-), nitrite (NO2-), ammonia (NH3), or more likely ammonium (NH4+). Some plants prefer one form over the other, like citrus prefer nitrate, however, typically acid loving plants like blueberries do not like nitrate and it can be toxic to them.

There are biological and physical processes in nature that convert atmospheric nitrogen to fixed nitrogen. Bacteria in the nodules of legumes are capable of converting atmospheric N to fixed nitrogen. Lightening is also capable of producing ammonia from air. Man has also learned how to convert atmospheric N to ammonia in a similar process called the Haber-Bosch process using heat and electricity.

There are also processes in nature that convert fixed nitrogen (fertilizer) back into atmospheric N. This is an important process in wetlands that helps remove nitrogen from our water and waterways. The process is a bacterial process called denitrification and converts nitrate into atmospheric N. There is also a bacterial process called nitrification that converts ammonia (or ammonium ions) into nitrate. These two processes are often coupled at an oxic/anoxic boundary in sediments and soils.


There are also some mined sources of nitrogen fertilizers, like nitrate in Chile.