The nitrogen cycle Nitrogen is essential for plant growth. Factors such as soil moisture, aeration, temperature, pH, and microbial breakdown of soil organic matter influence the availability of nitrogen to plants. The availability of nitrogen increases through application of inorganic or organic fertilizers to the soil. Mineralization Nitrogen availability to plants also increases through mineralization.
Ericaceous plants are an exception.
Nitrification occurs most efficiently when soil pH is between 5.5-6.5. Nitrification can be completed within two to four weeks. Immobilization Other factors decrease nitrogen availability to plants. This gaseous ammonia is lost into the atmosphere. Fertilizer runoff is another critical source of nitrogen loss.