Influences of spring and summer sowing on growth period of different soybean germplasms

Total of 67 soybean germplasms，including 57 internal ones and 10 foreign ones，were sowed in spring and summer，respectively，to study the effects of sowing date on growth period of different soybean germplasms. The results showed that compared with the original growth period，as to the germplasms sowed in spring，the growth periods of 16 germplasms got shorter，12 germplasms varied < 5 d，and 39 germplasms became longer. The biggest reduction in growth period of 33 d occurred in germplasm，Suinong No. 6，and the biggest increase in growth period of 54 d occurred in germplasm Panshidou. Compared with the original growth period，as to the germplasms sowed in summer，the growth periods of 27 germplasms got shorter，28 germplasms varied < 5 d，and 12 germplasms became longer. A significant reduction of growth period of 55 d happened in germplasm Jiyu 30. Averagely，the growth periods of germplasms sowed in summer were shorter than those of germplasms sowed in spring，because the germplasms sowed in summer possessed a shorter period at the flowering and podding stages. In term of accumulated temperature，the soybean sowed in summer averagely needed less than those sowed in spring. The reduction of need for accumulated temperature for soybean sowed in summer mainly occurred during flowering and podding stages.