Available nitrogen in soil

Available nitrogen in soil is the amount of nitrogen that plants can use, and it includes nitrate (NO3) and ammonium (NH4). The amount of available nitrogen in soil depends on the type of soil, the amount of organic matter, and other factors. Nitrate-nitrogen (NO3-N) measures the amount of available nitrogen in the soil that can be absorbed immediately by plants. The amount required in the soil for specific crops varies from crop to crop, but in general the levels should not fall below 10 mg/kg and should not exceed 50 mg/kg.