Abstract: A 14 d incubation test at 60% WHC and 25 ℃ was conducted to study the effects of fungicide chlorothalonil at its application rates of 0, 5.5 mg·kg^-1(field application rate, FR), 110 mg·kg^-1 (20FR) and 220 mg·kg^-1 (40FR) on the nitrous oxide (N₂O) and carbon dioxide (CO₂) emissions from acidic, neutral, and alkaline soils. The results indicated that the effects of chlorothalonil on the two gases emissions depended on its application rate and soil type. Comparing with no chlorothalonil application, the chlorothalonil at 20FR and 40FR inhibited the N₂O emission from acid soil significantly, while that at FR, 20FR and 40FR stimulated the N₂O emission from neutral soil, with the strongest effect at FR. Higher application rates (20FR and 40FR) of chlorothalonil inhibited the N₂O emission from alkaline soil at the early stage of incubation, but stimulated it at late incubation stage. Chlorothalonil at FR had no obvious effects on the CO₂ emission from test soils, but that at 20FR and 40FR promoted the CO₂ emission from acid soil while inhibited it from neutral and alkaline soils significantly.

Key words: N fertilizer operation, direct seeding rice, irrigation mode, population quality, yield