[Nitrous Oxide Production in Response to Oxygen in a Solar Greenhouse Vegetable Soil].

To explore the sources of peak nitrous oxide (NO) flushes in solar greenhouse vegetable field, an experiment was conducted with two conventional vegetable soils under different initial volume fractions of oxygen (O) (0%, 1%, 3%, 5%, and 10%). A robotized incubation system was employed to analyze the gas kinetics[O, NO, nitric oxide (NO), nitrogen (N), and carbon dioxide (CO)] every 6 or 8 h and calculate the NO/(NO+NO+N) index. Sodium chlorate (NaClO) was used to inhibit the oxidation of NO to further explore the relationship between NO and nitrite (NO). A parallel off-line incubation in triplicates was conducted under similar conditions to measure the dynamic changes in inorganic nitrogen content[ammonia (NH), nitrate (NO), and NO]. The results showed that NO production under anaerobic condition was significantly higher than that under aerobic condition. The peak value of NO in the soil collected from a straw-added plot (DIS) was significantly higher than that in the soil from non-straw added plot (DI) (<0.01) when the volume fraction of oxygen was ≤ 1%. Oxygen can directly affect NO production by delaying or inhibiting NO reduction, with significant increase in NO production rate under oxygen-depleted condition. However, the Nproduction rate decreased significantly with increase in initial oxygen volume fraction (<0.01). When the initial volume fraction of oxygen was between 1% and 5%, a continuous accumulation of NO was observed during the incubation period, resulting in the significantly higher NO/(NO+NO+N) index than that in either anaerobic or 10% of oxygen treatments. Furthermore, a linear correlation was observed between NO and NO at 5% and 10% of oxygen with the addition of NaClO ( ≥ 0.85). Incomplete denitrification and nitrifier denitrification from NO induction co-occurred in the range of 1% and 5% volume fractions of oxygen, significantly increasing the soil NO production and NO/(NO+NO+N) index. In addition, NO production under anaerobic condition was significantly higher than that under aerobic condition (<0.01).