Study On The Relations Between Growth Development And Yield Formation Of Alfalfa And Climate Conditions

This paper carried out research on growth development and yield formation of alfalfa and climate conditions from different aspects, such as phenophase, growth traits, photosynthesis characteristic, soil water and hay yield of alfalfa with different dormancy grade. Results were as follows1. Alfalfa reviving critical temperature was begining day of daily avaerage 5℃in Guanzhong region. The earlier 5℃begining day came, the earlier alfalfa revived. Contrarily, The later 5℃begining day came, the later alfalfa revived. It was about 15 days from 5℃begining day to reviving period. Namely, when cumulative temperature or effective accumulated temperature above 5℃reached respectively 89.64℃or 30.78℃, alfalfa would go into greening period.2. It required 72 days and 958.23℃accumulated temperature above 5℃from reviving period to efflorescence period for the first growth season of alfalfa, 84.86 days and 1233.51℃from reviving period to pod period. Thereinto, It required 31.43 days and 958.23℃from reviving period to branching period; 26.43 days and 425.26℃from branching period to bud period; 14 days and 246.64℃from buding period to efflorescence period; 12.86 days and 272.37℃from efflorescence period to poding period.3. Alfalfa each growing phase length had positive correlation with mean temperature, significantly positive correlation with accumulated temperature above 5℃. According to effective accumulated temperature theory, each growing phase lower limit temperature index could be educed. Therefor, lower limit temperature from reviving period to branching period was 5.68±0.61(℃), from branching period to buding period 13.95±1.78(℃), from buding period buding period to efflorescence period 17.37±3.00(℃), from efflorescence period to poding period 21.83±0.95(℃).4. Alfalfa was cut three times a year in efflorescence period, but the fourth cutting was in branching later in 2004.There were different interval days and accumulated temperature above 5℃in different growth and development phase. It was about 200 days and 3697.9℃from reviving period to last cutting, 72 days and 958.23℃from reviving period to efflorescence period for the first growth season, 38 days and 801.14℃from the first cutting to efflorescence period for the second growth season , 43 days and 1107.39℃from the...