中文摘要：

为了解秋季刈割对紫花苜蓿根贮有机物质在越冬期间变化情况及对翌年越冬率、头茬产量的影响,本文以‘公农1号’紫花苜蓿为试验材料,测定第二次刈割后900GDD,1000GDD,1100GDD,1200GDD刈割的紫花苜蓿在2013年秋末至2014年初春越冬期间主根中非结构性碳水化合物和含氮化合物的含量。结果表明：种植翌年,第二次刈割后1000GDD刈割的紫花苜蓿越冬率及头茬产量显著高于其他刈割处理（P〈0.05）,与未刈割处理间差异不显著;整个越冬期间,紫花苜蓿根贮藏性有机物质含量呈先上升后下降的趋势。综上所述,吉林省中东部地区秋季刈割具有可行性,且在第二次刈割后1000GDD时刈割不会影响牧草翌年产量。

英文摘要：

In order to explore the fall harvest at different GDD affects roots organic reserves in alfalfa,over-winter rate and the yield at the first harvest the following year were investigated in middle-eastern section of Jilin Province from 2013 to 2014with Medicago sativa L.cv.Gongnong No.1.Fall harvest treatments were no additional fall harvest or a third fall harvest applied at 900,1000,1100,1200 growing degreedays（GDD）after the second harvest.Measured root concentrations of total nonstructural carbohydrates and N reserves during overwinter,and the results showed that the over-winter rate and the first harvest yield in the third harvest taken at 1000 GDD after the second harvest were significant higher than that of other fall harvest treatments（P〈0.05）,and no significant difference was found between no additional fall harvest treatment.During the winter,root total nonstructural carbohydrates and N reserves of alfalfa were increased initially and then reduced.In conclusion,it′s available for fall harvest in middle-eastern section of Jilin Province as long as an interval of 1000 GDD was kept between the last summer harvest and the fall harvest.