Abstract: Field measurements conducted in the farms of Southwest Agricultural University and South China Agricultural University showed that long term flooding was the main factor causing high CH₄ emission during the rice growing period in Southwest China. The longer the soil was dried before flooding, the less the CH₄ emission during the rice growing period. But the effect was available only for one rice crop season. The mean CH₄ emission over rice growing period was reduced by 63～72% by draining traditional winter-flooded rice fields and planting winter wheat. If the drainage and irrigation system could be improved significantly and the crop rotation of one flooded rice and one upland winter crop could be introduced instead of one rice crop in the area of the traditional winter-flooded soils, the soil production could be raised and total CH₄ emission from rice fields could be reduced significantly.

Key words: Water management in winter, Rice field, CH₄ emission