关键词: 播期, 直播早稻, 产量, 适宜播种期, 区域划分

Abstract: Jiangxi, as one of the largest double rice cropping area in China, affected by the shortage of rural labor force and the increase of labor cost, the planting mode of direct sowing early rice changed from transplanting to direct seeding. In spring, the climate conditions were complex and the temperature fluctuation was large, which was unfavorable to the direct sowing early rice seeding. At present, the sowing date of direct seeding early rice was uncertain, and the phenomenon of blind direct seeding was common, which was unfavorable to the stable yield and high yield of direct sowing early rice. To reveal the impacts of sowing date on yield, seedling rate, and phenological stage of direct sowing early rice, an experiment with nine sowing dates was conducted at Nanchang country in Jiangxi province in 2017−2018, in which the rice variety of Zhongjiazao17 and Zhongzao35 and Zhongzao39 were used. The nine sowing dates were March 6(denoted as B1), March 11(denoted as B2), March 16(denoted as B3), March 21(denoted as B4), March 26(denoted as B5), March 31(denoted as B6), April 5(denoted as B7), April 10(denoted as B8), and April 15(denoted as B9). The temporal and spatial variation of the earliest safely direct sowing date were analyzed in Jiangxi in past 59 years(1961−2019). The results showed that, the whole phenological stage of B9 was shortened by 21−25 days compared with B1 as the sowing date was delayed. The effect of sowing date on seedling rate, effective panicle number, grain number per panicle, and 1000−grain weight of direct sowing early rice was significant. And when the seedling rate reached 50% or above, sufficient basic seedlings and effective panicle number could be expected to ensure a high yield, under the conditions of this experiment. The safely direct sowing initial temperature was 11.64℃ for the testing varieties, to obtain a seedling rate of 50% or above. For this temperature threshold index, the safely direct sowing date of early rice was well in advance in Jiangxi in past 59 years, and the earliest date was on March 29 in northern Jiangxi, March 28 in central Jiangxi and March 21 in southern Jiangxi in 2011−2019. The safely direct sowing date under 80% guarantee rate were estimated by each meteorological stations, which could be referred in production arrangement in the regions nearby.

Key words: Sowing date, Direct sowing early rice, Yield, Suitable sowing date, Regional division