What does Plant Available Nitrogen (PAN) refer to?

Plant Available Nitrogen (PAN) specifically refers to the portion of nitrogen in biosolids that is readily available for plant uptake. This concept is crucial in nutrient management as it focuses on the nitrogen that plants can effectively utilize for growth and development.

Biosolids are organic materials generated during the treatment of sewage. They contain various forms of nitrogen, including organic nitrogen and inorganic forms like ammonium and nitrate. However, not all nitrogen in biosolids is accessible to plants; only specific fractions can be assimilated efficiently. Therefore, understanding PAN helps in evaluating how much of the nitrogen content can actually contribute to plant growth when applying biosolids to agricultural or horticultural systems.

The other options provide broader or unrelated contexts about nitrogen. For example, not all nitrogen in the soil is available for plant use at any given time, as some forms may be locked in organic matter or in forms that plants cannot utilize directly. The measure of nitrogen fixed by legumes pertains to a biological process that does not directly equate to measuring PAN specifically from biosolids. Lastly, the total nitrogen content of composted materials includes all nitrogen forms, without specifying how much is available for plant use, which again does not align with the definition of PAN. Thus, the