翻耕与播种间隔时间对后茬苜蓿生长的影响

Effect of the interval between ploughing and sowing on growth of continuous cropping alfalfa

紫花苜蓿（Medicago sativa）自毒作用对连作种植的苜蓿建植有不利影响，减轻自毒作用，使苜蓿的更新建植能够成功，是苜蓿生产中的一个重要问题。为此，在北京地区进行了田问试验，对生长5年紫花苜蓿土地在不同时间耕翻，间隔0、15、30、45、90d之后再播种同品种苜蓿，以研究耕翻至播种间隔时间对苜蓿苗期生长及生化特性的影响。结果表明，随着耕翻至播种间隔时间的缩短，苜蓿苗期根和苗的长度与质量均呈明显下降的趋势。与间隔30、45及90d播种的苜蓿相比，耕翻当天直接播种的苜蓿苗根系发育明显受到抑制，根长下降了10％～23％，苗长下降了16％～26％，根质量下降了58％～71％，苗质量下降了38％～62％。苗期苜蓿叶绿素含量随间隔时间变化不明显，但超氧化物歧化酶和过氧化物酶活性随间隔时间延长而降低。

Autotoxicity often causes poor establishment of continuous cropping alfalfa, therefore reducing the autotoxicity will benefit successful alfalfa regeneration in continuous cropping. A field experiment was conducted in the Beijing regions to determine effect of the interval between ploughing and reseeding on growth of continuous cropping alfalfa in 5-years field. The treatments included 0, 15, 30, 45 and 90 days of interval between ploughing and reseeding. The results of this study showed that less interval between ploughing and reseeding reduced the length of root and shoot and the weight of root and shoot of the alfalfa plants. The root length, shoot length, root weight and shoot weight in plots with 0 day interval reduced the 10%-23%, 16%-26%, 58%-71% and 38%-62% ,respectively when compared to those in plots with a interval of 15, 30, 45 and 90 days. The changes of the interval did not affect chlorophyll content while the activities of SOD and POD increased with the decrease in interval between ploughing and reseeding.