Study On The Relations Between Growth Development And Yield Formation Of Alfalfa And Growing Degree-days (GDD) In Songliao Plain

This paper carried out research on growth development and yield formation of alfalfa in SongliaoPlain and growing degree-days from different aspects, such as growth characteristics and hay yield ofalfalfa in sowing date, phenological period, spring and fall cutting period from 2013 to 2014. Resultswere as follows:1. The results showed that there was a significant(P<0.05) positive correlation between emergencedays and growing degree-days(GDD) before winter and there was a significant(P<0.05) positivecorrelation between growth characteristics and winter abilities.2.The height, diameter of crown, depth of crown and shoots before winter, overwintering rate,yield in the following year of alfalfa sowing during 1400-2400 GDD before winter weresignificantly(P<0.05) higher than other sowing date treatment. According to the regression equationfrom 1st cutting to 3rd cutting, the optimum GDD before winter was 2200℃ d due to the yield was thehighest respectively. Different sowing dates made little influence on FW/DW Ratio, Stem/Leaf Ratio.3. It required 61 days and 987.6℃ d accumulated temperature above 5℃ from reviving period toefflorescence period. Thereinto, it required 15.2 days and 109.24℃ d from reviving period to branchingperiod; 32 days and 567.12℃ from branching period to bud period; 13.8 days and 311.2℃ d frombuding period to efflorescence period; 11.6 days and 279.16℃ from efflorescence period to podingperiod.4. Lower limit temperature and GDD from reviving period to branching period was 5.17±1.16 and38.18 ℃ d, from branching period to buding period 15.91±0.24 and 90.16 ℃ d, from buding periodbuding period to efflorescence period 17.61± 0.92 and 76.6 ℃ d, from efflorescence period topodingperiod 22.56±1.02 and 23.96 ℃ d. GDD in whole developing stage of alfalfa was 1267.76 ℃ d.5. Logistic model characteristic parameter of the plant height growth and GDD indicated: scope ofGDD and growth phase that turning points of alfalfa height quick growth period were: the first stubblefor 308.292-684.565℃ d, the second for 249.853-456.322℃ d, the third for 425.779-581.689℃ d.GDD at their maximal instant growth rate respectively were 496.429, 353.088 and 503.734℃ d. Scopeof GDD and growth phase that turning points of alfalfa quick dry matter accumulation period were:stem dry matter for 54.900-642.392℃ d,leaves dry matter for 91.207-1007.474℃ d, total dry matterfor 91.519-719.606℃ d. GDD at their maximal instant growth rate respectively were 348.1,515.3 and384.2℃ d.6. The regression analysis shown in this study is a quadratic regression relationship betweenquality character and GDD before winter. According to the regression equation, GDD increased 100℃d, and then NDF properties increased 4.1 percentage point, ADF properties increased 2 percentage point,CP properties decreased 1.3 percentage point, RFV decreased 19.9 percentage point respectively.According to the regression equation the optimum GDD was 684℃ d due to the CP properties was40%.7. The results showed that compared with the CK(not mowing) treatment, the overwinter rate andyield of alfalfa reduced.There was no significant(P>0.05) between CK and 1000 GDD at the secondcutting and significant(P<0.05) with other treatment. So, it’s available for fall cutting in Songliao Plain.The concentration of reserve in alfalfa root was lower significantly for cutting at 1100 GDD after thesecond cuttingthan the other treatments before winter.