两系法杂交水稻具有4个特点,一是大穗优势,二是中期优势,三是后期早衰明显.四是易出现基本苗不足、最高苗数不足、穗数不足。 据研究,两系杂交稻前期禾苗处于幼小阶段,插植的基本苗数有限,单位土地面积上的净光合生产率很低,后期又有早衰,因而高产的形成主要依赖于中期。干物质迅速增加的时期,早稻是插后25～50天,晚稻为插后20～50天。中期的栽培管理:第一是保证大穗 Two-line method hybrid rice has four characteristics, one big spike advantage, the second is the mid-term advantage, the third is the late premature aging obvious. Fourth, prone to lack of basic seedlings, the maximum number of seedlings inadequate spike number. According to the research, early seedlings of two-line hybrid rice are young and have a limited number of seedlings planted. The net photosynthetic rate per unit area is very low and there is premature decline in the later stage. Therefore, the formation of high yield mainly depends on the medium term. Dry matter rapidly increased period, early rice is inserted 25 to 50 days, late rice is inserted after 20 to 50 days. Medium-term cultivation and management: The first is to ensure large ears