Abstract: In order to guide potassium management for alfalfa,the potassium characteristics in different aged alfalfas including one-,two-,three-,four-,and six-year old alfalfa were studied in 2007 using field trial and laboratory measurement.The results show that the potassium content in the aboveground part of alfalfa decreased generally along with the increasing of the growing year,especially at the first cutting time.The potassium content of different aged alfalfas at the fourth cutting was obviously lower than that at the former three cuttings.With the increasing of the growing year,the potassium content and potassium accumulation in the root were increased.The content of total and available potassium in different soil layers decreased,but the extent reduced gradually,with the planting years increasing.In 0~50 cm soil layer,the content of soil total and available potassium in different aged alfalfas showed a pattern of decrease at first and then increase along with the depth increasing of the soil layers.The content of available potassium in 20~30 cm soil layer was lower than that in the other layers.In summary,the potassium requirement at the fourth cutting time and relatively lower potassium content in the 20~30 cm soil layer should be considered when dressing of potassium fertilizer to alfalfa fields.

Key words: Alfalfa, Growing year, Potassium absorption characteristics, Soil potassium content

摘要： 2007年以播种当年、生长第2、3、4、6年紫花苜蓿(Medicago sativa L.)为试验对象,采用田间试验和实验室研究相结合的方法,对不同生长年限紫花苜蓿的吸钾特征进行研究,旨在为苜蓿钾素(K)养分管理提供理论依据.结果表明:紫花苜蓿地上部分K含量总体随着生长年限增加而降低,尤以第1茬最为明显;各生长年限苜蓿第4茬K含量明显低于前3茬;根系K含量随生长年限增加而升高,根系K积累量逐年增加;随着生长年限的延长,苜蓿地各土层土壤速效K和全K含量总体呈下降趋势,且降幅逐渐减小;在0~0cm土层内,不同生长年限紫花苜蓿地土壤速效K和全K含量均随土层深度增加呈先降后升的变化趋势,20~30cm土层K含量相对较低;苜蓿追施K肥应充分考虑第4茬苜蓿对K的需求和20~30cm土层K含量较低的特点.

关键词: 紫花苜蓿, 生长年限, 吸钾特征, 土壤钾含量