Effects Of Cutting Frequency On Forage Yield And Quality And Cold Tolerance Of Alfalfa

Alfalfa (Medicago sativa L.) is a forage of the worldwide largest planting-area and the widestherbage in application, which has good palatability, high protein content and general nutritivevalue.Cutting is the main use type of alfalfa, cutting frequency not only affects forage yield and itsquality this year, but also has influence on its winter surviving rate and lasting application.In the research,field experiment that ZD,AO,HP and AE having been planted for two yearswere cut 1,2,3,4 individually was performed,Yield,CP, winter surviving rate and relatedphysiological Indexes of cold tolerance had been determined.The main research results fellow asbelow:1.In second-year plantation(2005),when AE was cut 4 times, hay yield was the highest; withcutting 1 time of former year, when ZD was cut 4 times, hay yield of 2006 was the highest; whenZD was 3 times in 2005 and 4 times in 2006, the total hay yield was the highest.2.In second-year plantation (2005),when HP was cut 4 times, the average CP content was thehighest; with cutting 4 times of former year, when AO was cut 4 times, the average CP content of2006 was the highest; when HP was cut 3 times in 2005 and 4 times in 2006, the two-year averageCP content was highest.3.Cutting frequency had direct effect on winter surviving rate. With cutting frequencyincreasing, winter surviving rates of 4 cultivars gradually reduced. By treatment of different cuttingfrequency, winter surviving rates of ZD and AO were significantly higher than that of AE and HP.4.With cutting frequency increasing, MDA content and relative conductivity rate in alfalfacrowns cells were obviously increased before overwintering.With cutting frequency increasing,activities of POD and SOD of 4 cultivars were decreased.5.With cutting frequency increasing,contents of soluble sugar, starch,free amino acid andsoluble protein in alfalfa were decreased.With treatment of different cutting frequency, these mattersappeared positive correlation to overwintering.According to regression analysis,contents of solublesugar and starch had the main action on winter surviving rate,among which,soluble sugar contenthad direct affect,and starch content had indirect affect on it by transforming into soluble sugar.Withcutting frequency increasing,root C/N of ZD and AO were increased little,and changed slowly;rootC/N of HP and AE were declined gradually, and changed rapidly.6.According to grey relevancy analysis, the results of two years experiment were showed that,by comprehensive evaluation of alfalfa forage yield, quality and cold tolerance, the best cultivarwas ZD,the optimal combinations of cutting frequency (cutting frequency in 2005,cutting frequencyin 2006)were sequentially 2 times,4 times;2 times,3 times;2 times,2 times.