"Soil stores, moderates the release of and cycles nutrients and other elements," according to the National Resources Conservation Service. The biochemical process of nutrient cycling in the soil changes elements into the nutrients that are used to create food. When the natural cycle of creation of nutrients in the soil is disrupted, food becomes unhealthy. The global overuse of nitrogen in synthetic fertilizers has caused a disruption in nutrient cycling.
Healthy plant growth requires 13 essential nutrients in soil. The same nutrients are needed for healthy human growth. Nitrogen, phosphorus and potassium are primary nutrients; sulfur, calcium and magnesium are secondary nutrients. The remaining seven nutrients are called micro-nutrients. Nitrogen, phosphorus and potassium (NPK) are needed in the largest amounts. Nitrogen is needed in the largest quantities and is the most commonly applied synthetic fertilizer.
All essential nutrients are in plant and animal materials that naturally decompose in soil. Their decomposition creates the nutrient cycle that feeds soil and the growth of more plant life. Plants are broken down slowly over time or in the sped-up process known as composting. Life forms such as bacteria, fungi and worms in the soil digest decaying plant life, taking the nutrients into their bodies and releasing them into the soil.
Living organisms help decompose plant materials. When earthworms and other organisms eat decaying plants, carbon and nutrients are released to the soil. Fungi break apart plant compounds and create smaller compounds. Bacteria then break these into even smaller compounds. Plant material is thus reduced to nutritious elements that are again cycled through plant roots for new plant growth.
Nitrogen is the nutrient essential to plant growth in the largest quantities, but "it is possible to have too much of a good thing," according the World Resources Institute report on nitrogen overload. Synthetic fertilizer used since 1940 has doubled the nitrogen content in the environment, disrupting all life ecosystems. Nitrogen overload is a major cause of pollution and its severe health problems.
Nitrogen overload caused by the use of synthetic fertilizer unbalances the normal nutrient cycling in soil. Soil loses calcium, potassium, magnesium and other essential elements and becomes lifeless and unable to produce growth without the artificial stimulation of more synthetic nitrogen fertilizer. Soil in this condition looks gray, dull and lifeless. Food grown in soil that has lost its essential nutrient cycling is devoid of nutritional value.