Key Factors, Soil Nitrogen Processes, and Nitrite Accumulation Affecting Nitrous Oxide Emissions

Core Ideas Nitrite concentration was highly correlated with N 2 O emissions within two distinct water content ranges. Soil moisture was the most important environmental factor affecting N 2 O emissions. Nitrous oxide emissions increased exponentially as the N application rate increased. Biochar and N transformation inhibitors showed great potential to reduce N 2 O emissions. A better understanding of the factors and processes affecting N 2 O emissions is essential for developing mitigation strategies. This research aimed to examine the factors and processes affecting N 2 O emissions and N dynamics. Laboratory incubation experiments examined the effects of N (urea) application rate (0–150 mg N kg ‐1 ); soil water content (5–30%, w/w); temperature (10–40°C); and incorporation of biochar (1%, w/w), a urease inhibitor (Agrotain Ultra), and a nitrification inhibitor (N‐Serve 24) on N 2 O emissions and N transformation dynamics in a Hanford sandy loam soil. Nitrous oxide emissions, soil pH, and mineral N species were monitored for 35 d. Peak emission rates and cumulative losses of N 2 O increased more than the N application rate increased. Soil water content at 20 and 30% [above the water holding capacity (WHC) of 12%] resulted in much higher total N 2 O emissions (9.3 and 8.0% of total soil inorganic N, respectively) than that from 5 and 10% water content (0.2 and 0.3%, respectively). Increasing soil water content above WHC caused higher N 2 O emissions than increasing the soil temperature, which demonstrates that soil moisture is more significant in affecting the process. Nitrite concentration was highly correlated with N 2 O emissions within two water content ranges (above or below WHC). Amendment with biochar, Agrotain Ultra, and N‐Serve 24 reduced N 2 O emissions by 74, 78, and 74%, respectively. This research provide further understanding of the processes affecting N 2 O emissions from soil, which can assist in developing management practices.