Effects Of Enviroments On The Winter Hardiness Of Alfalfa

Alfalfa(Medicago sativa L.)is an important leguminous forage widely culticated in the world. Lower temperature in winter becomes a key point of restricting the alfalfa's growth in Northern High Latitudes China. In this paper, Alfalfa were two cultivars with differernt winter hardiness(Gongnong NO.1,Haygraze). We accessed the changes of soil temperature and soil moisture to analysis their relationship with winter hardiness and yield. The results showed that:(1) At the beginning of the freeze, the stability of the freeze period, freeze-thaw period, variation trends of soil temperature of irrigated field were similar to that of the comparison. Daily range of soil temperature of the irrigated field is lesser and the soil moisture was higher in the freeze-thaw period than freeze-up before. Under irrigated condition, there was improvement of winter hardiness and yield of two cultivars of alfalfa. That is especially for Haygraze the weakly winter hardiness alfalfa varieties.(2) The existence of snow will not only insulate the heat loss from ground,thus raising the ground temperature,but also delay the effects of external conditions on thermal state of frozen soil due to it is low conductivty and large capacity of heat. In the conditions(overlying snow,natural snow and no snow), winter hardiness and yield of Gong nong No.1 were higher than Haygraze.Cold resistance of no snow alfalfa was induced sharply. Snow is good for winter survival of alfalfa.(3) For researching the effect of different tillage managements on soil temperature and soil moisture in cold farming areas,the test plot was established. The testing results indicated there was avisible regulating effect in soil temperature and soil moisture with furrow sowing. Comprehensive evaluation of characteristics including cold resistance and production perofrmance of 3 planting patterns indicated that ridge planting was the lowest than others,although furrow planting is higher than traditional cultivation,the difference was not significant(P> 0.05).(4) Alfalfa fields covered in different periods compared with the control, there has been an increase in soil moisture. Either Gong Nong No.1 or Haygraze covered at the beginning of the soil freeze had the best effect and the most excellent winter hardiness, and compared with others covered in other periods, there is significant difference. (P<0.05)Cover the soil before soil freezing stay steady and the beginning of the freeze-thaw during the spring respectively. Haygraze the weakly winter hardiness alfalfa varieties express the Difference of winter hardiness Between the two periods(P<0.05),but for Gong Nong No.1 with excellent winter hardiness the difference of winter hardiness was not obvious(P>0.05).