增产的主要贡献是双穗率提高，空秆率下降——每公顷有效穗数的增加。
The increasement of double ears and the decrease of empty stalk were main reason for obtaining high yield because their agronomical characters did not obviously changed.
无效株是影响群体整齐度的重要因素，主要包括：自交株、空秆、小穗株及病虫害株等。
The main factor that affects population's uniformity is invalid plant including inbred lines, barren stalk rate, diseases and pest insects plant in populations of different yield level.
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