Fall Dormancy And Snow Depth Effects On Winter Hardiness And Yield Of Alfalfa

The purpose of this study was to study the effect of snow cover thickness on cold resistance and yield of alfalfa. 0 cm, 10 cm, 15 cm and natural snowfall set four different snow cover thickness by of dynamic observation of alfalfa canopy temperature and surface soil(0-30 cm) hydrothermal change, study different snow cover thickness, different fall dormancy. Alfalfa cold resistant physiological response and snow how to influence alfalfa spring regrowth and snow on alfalfa forage yield with systematic analysis, this paper obtained the following conclusions:1. Snow on the coverage has a significant impact of soil surface temperature. Freezing period, with the increase of thickness of the overlying snow, snow can weaken the response of alfalfa canopy temperature and soil temperature of atmospheric temperature, can improve the surface soil moisture content. During the melting period, as the snow melts, the water content of the surface soil has increased significantly, but the more the thickness of the snow, the more slowly the soil temperature will rise.2. Each fall dormancy of alfalfa root neck in malondialdehyde(MDA) and soluble protein soluble protein(SP) content and the change of temperature correlation better, and the root soluble carbohydrates water soluble carbohydrate(WSC) content change with temperature is not a good trend. Under the condition of no snow cover, as the canopy temperature changed significantly, compared with the amount of SP and MDA accumulated in the canopy of the snow covered treatment groups, there was no obvious trend in the MDA and SP contents in the snow covered treatments.3. The snow cover can effectively improve the alfalfa winter surviving rate(WSR), no snow cover conditions, Non-dormancy type(ND)(with the exception of Sardi7) and extremely non-dormancy type(ED) death, dormancy type(DM) and semi-dormancy type(SD) alfalfa WSR 52.14~67.38%, and different fall dormancy level between WSR difference was not significant(P>0.05). With the increase of thickness of the overlying snow, WSR of different fall dormancy alfalfa significantly increased(P<0.05), but the snow covered(except Sardi10 and WL712) of WSR difference was not significant(P>0.05).4. The use of membership function method for comprehensive evaluation of cold resistance, the conclusion:(1) 0 cm snow depth, the cold hardiness of sorting for(death alfalfa varieties do not take part in the ordering): Concept >Caribou AC >Alfaqueen = PGI427 >Magna551 > Victorian >Sardi7;(2)10 cm snow depth, the cold hardiness of sorting for: Concept >PGI427 =Sardi7 >Caribou AC >Magna551>Alfaqueen >WL525HQ=WL656HQ> Victorian> Sardi10 >WL712;(3) 15 cm snow depth, the cold resistant sort: Concept>AC caribou = Magna551 >PGI427 >Victorian =Sardi7 =WL656HQ >Alfaqueen=WL525HQ =Sardi10> WL712;(4) Natural snow, the cold hardiness of sort: PGI427 >AC caribou=Concept = Magna551 >Victorian =Sardi7 >Alfaqueen =WL656HQ >WL525HQ=Sardi10>WL712.5. No snow cover conditions, except death 8~11 grade alfalfa varieties, the rest of the alfalfa varieties of green up is snow covered treatment group delay 8-20 d. The snow covered 10 cm, WL712 and Sardi10 green period is 15 cm and the snow cover natural snowfall delayed 3-5 d. The snow cover between the green stage, the target of 4 grade and 5 grade Magna551 giant green earliest(March 20th). The fall dormancy alfalfa regreen sooner or later following order: SD, DM, ND, ED.6. With the increase of thickness of the overlying snow, the number of different fall dormancy alfalfa branch shoots(BS) and plant high(HP) were significantly increased(P < 0.05), and under the conditions of natural snowfall reached the maximum. Under the condition of snow covering, Concept BS was the highest176.66, reindeer of HP was the highest 73.67 cm; snow covered, Magna551 BS was the highest 270.31, HP86.67 cm.7. The order of the yield of each fall dormancy alfalfa was: first cut yield>second cut yield >third cut yield>fourth cut yield. The yield of the same fall dormancy alfalfa varieties with different snow cover thickness is natural snow>15 cm snow depth>10 cm snow depth >0 cm snow depth. 0 cm snow depth, giant Magna551 grass yield the highest 923.61kg/667m2; with the increase of thickness of the overlying snow,different fall dormancy alfalfa grass yield were under the conditions of natural snowfall reached maximum,Magna551 in the snow covered with grass yield were the highest.