Nitrogengjenvær

Nitrogengjenvær describes the persistence or residence time of nitrogen in an environment after it has been introduced, such as through fertilizer, manure, plant residues, or atmospheric deposition. The concept is used in agronomy, soil science, and environmental planning to assess how long nitrogen remains in a system and how it cycles through biological and physical processes.

Nitrogen in soil exists in inorganic forms (ammonium NH4+, nitrate NO3−) and in organic forms bound in soil organic matter. Microbial processes drive transformations that determine nitrogengjenvær: mineralization converts organic nitrogen to inorganic forms; immobilization temporarily ties inorganic nitrogen into microbial biomass; nitrification converts ammonium to nitrate; denitrification returns nitrogen to N2 or N2O gases under low oxygen conditions. In addition, ammonia can volatilize, and nitrate can leach with percolating water; runoff can remove nitrogen from fields. The rate and extent of persistence depend on climate, soil texture, moisture, organic matter, crop uptake, and timing of inputs.

High nitrogengjenvær can increase the risk of groundwater contamination by nitrate, contribute to eutrophication of surface waters, and influence emissions of nitrous oxide, a greenhouse gas. Scientists estimate persistence using measures such as net mineralization rates, cumulative inorganic nitrogen in soil, and models of nitrogen turnover. The concept is related to nitrogen use efficiency and environmental fate.

Management aims to reduce excessive persistence by aligning inputs with crop needs, applying fertilizers when plants can take them up, using slow-release forms or inhibitors, employing split applications, growing cover crops, incorporating residues, improving soil structure, and creating buffer zones to reduce runoff.

See also: nitrogen cycle, nitrogen use efficiency, eutrophication, soil science.