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Plants require more nitrogen (N) than any other nutrient but only a small portion of the nitrogen in soil is available to plants; 98 % of the nitrogen in soil is in organic forms. Soil microorganisms convert organic forms of nitrogen to mineral forms when they decompose organic matter and fresh plant residues.
In this manner, what is available nitrogen in soil?
Available nitrogen is defined as nitrogen in a chemical form that can be readily absorbed by plant roots. The nitrogen in soil is nearly all in the organic matter.
Similarly, how much nitrogen is in the soil?
Soils contain approximately 2,000 pounds of N in organic forms for each percent of organic matter. This portion of organic matter decomposes at a rather slow rate and releases about 20 pounds of N per acre per year for each percent of organic matter.
In heavy clay soil, Nitrogen is almost always too low, over watering the garden or heavy rains will leach it out of the soil. In heavy clay soil Phosphorus is almost always very high.