[Effects of high-yielding rice cultivar and cultivation pattern on methane emission from paddy field].

A field experiment was conducted to observe the effects of high-yielding rice cultivars (early rice Luliangyou No. 996 and Chuanfeng No. 1, and late rice T you No. 259) and cultivation patterns (direct sowing and transplanting) on the methane emission from paddy field. The methane emission from early rice field before drying was 52%-73% of the total, while drainage and drying decreased the methane emission significantly. For late rice field, the methane emission during vegetative growth stage was 70% of the total. Under direct sowing of early rice, the average methane flux was lower, but the total methane emission was higher, compared with those under transplanting. As for late rice, both the average methane flux and the total methane emission were higher under direct sowing than under transplanting. There existed significant differences in the methane emission per unit grain production of early rice and late rice between direct sowing and transplanting. The methane emission per unit grain production under direct sowing of early rice super hybrid was increased by 4.84 g CH4 x kg(-1), compared with that under transplanting, and the emission under direct sowing of conventional early rice was increased by 3.48 g CH4 x kg(-1), compared with that under transplanting. The emission under direct sowing of hybrid rice was 6.67 g CH4 x kg(-1) higher than that under transplanting. In the same cultivation area and the same time period of direct sowing and transplanting, the methane emission was in the order of direct sowing of conventional early rice > transplanting of conventional early rice > direct sowing of early rice super hybrid > transplanting of early rice super hybrid, and direct sowing of late rice > transplanting of late rice.