Mineral nitrogen (N), or N-min, refers to the amount of nitrate and ammonium nitrogen found in the root zone, i.e., the plant-available N in the soil at the time of sampling. N-min analyses are conducted on soil samples taken to a maximum depth of 100 cm, depending on the soil type. The samples are ideally collected as close to the fertilizer application time as possible. These samples are used to determine the economically optimal application of N, which is based on the total N needs of the crops; the amount of plant-available N present in the soil before fertilizer application (the N-min); as well as the quantity of plant-available N released during the growing season from applied organic matter, such as manure. The N-min analysis does have some limitations associated with soil type and crop type and is also most reliable in uniform fields. Nevertheless, in fields meeting these criteria, the analysis can provide valuable insights into the quantity of N already present in the soil. This information can guide the farmers decision on how much N should be applied to reach the economically optimal fertilization level, thereby avoiding the purchase and application of excess N.