[Nitric oxide production in rice soils (author's transl)].

Nitric oxide gas evolution from nitrite was studied in vitro in three rice soils by gas chromatography. Autoclaved soils showed an NO evolution when supplemented with nitrite. Yet, when temperature of incubation, soil pH, soil moisture content and nitrite concentration were varied in the three soils, and with addition of nitrite reductase inhibitors, it appeared in one soil that NO production was partially a biological process. Thus, NO formation was two times as high in non-sterile soil as in sterile soil, and decreased when the temperature increased. Optimal NO production occurred at about neutrality and increased with increasing soil moisture content; moreover, this NO formation increased much less than in the other two soils with increasing nitrite concentration. Finally, the first soil contained three times more denitrifying bacteria tolerating a high nitrite concentration (5 g/1) that the other soils.