Abstract: A field experiment was carried out to study CH4 emissions from rice field as affected by two levels of soil tillage intensity(digging tillage and rotary tillage) and three rice cultivation patterns(direct seeding,seedling throwing and hand transplanting).Results show that the same in rice cultivation pattern,the tillage intensity treatments,digging and rotary tillage presented the same trend of seasonal variation in CH4 flux.The effect of tillage intensity on total CH4 emission during the rice-growing period depended on rice cultivation pattern: compared with digging tillage,rotary tillage decreased CH4 emission significantly by 31.37% with seedling throwing adopted;and did not have much effect with direct seeding and hand transplanting adopted.Rice cultivation pattern had significant effects on seasonal variation of CH4 flux.The CH4 flux in direct seeding treatment showed roughly a "two-peak" seasonal variation curve,being relatively low at the early rice growing stage.The CH4 flux in transplanting treatments(seedling throwing and hand transplanting) displayed "three-peak" seasonal variation curve,being relatively high at the early rice growing stage and reaching the highest level on D12 after rice transplanting.With digging tillage,the total CH4 emissions,regardless of rice cultivation patterns,all increased,but did in the order of seedling throwing> direct seeding> hand transplanting.With digging tillage,compared with seedling throwing,direct seeding and hand transplanting decreased CH4 emission by 23.31% and 42.51%,respectively;with rotary tillage,total CH4 emission in the three rice cultivation patterns were almost the same.Reducing soil tillage intensity by using rotary tillage instead of digging tillage could reduce disturbance of soil,thereby decreasing CH4 emission from the rice field to some extent.Compared with rice transplanting,rice direct seeding could significantly decrease CH4 emission at the early rice growing stage,which obviously has some potential in CH4 reduction,but field water management needs to be intensified at the middle and late stages of the rice growing season.

Key words: rice field, direct seeding, seedling throwing, hand transplanting, soil tillage intensity, CH4 emission