Abstract: In order to explore the nitrogen utilization characteristics of alfalfa with different nitrogen efficiency in different growth periods,we conducted an outdoor nutrient liquid sand-culture experiment with four alfalfa varieties ("LW6010" "Gannong No.3" "Gannong No.7" and "Longdong") grown under 2 nitrogen levels (21 and 210 mg·L^-1) in four growth periods. The growth characteristics,root characteristics,nodulation characteristics,nitrogen metabolism enzyme activities and nitrogen accumulation were measured in each growth period. The results showed that with the plant growth,root characteristics and nitrogen accumulation reached the maximum in the mature period. Nodulation characteristics reached the maximum during pod setting stage,and nitrogen metabolism enzyme activity reached a maximum during blooming stage. Under low nitrogen level,the growth characteristics,root characteristics,nodulation characteristics and enzyme activities of "LW6010" and "Gannong 7" are higher than those of "Gannong 3" and "Longdong" alfalfa. Under high nitrogen level,the growth characteristics,root characteristics,nodulation characteristics and enzyme activity of "LW6010" and "Gannong 3" are higher than those of "Gannong 7" and "Longdong Alfalfa". In summary,the nitrogen-efficient alfalfa variety "LW6010" has a higher capability of nitrogen fixation,absorption and transformation than the low nitrogen-efficiency variety "Longdong" alfalfa.

Key words: Alfalfa, Nitrogen efficiency, Growth periods, Nitrogen utilization characteristics

摘要： 为探讨不同氮效率紫花苜蓿各生育期氮利用特征，本研究采用室外营养液砂培试验，选取4种不同氮效率类型的紫花苜蓿品种（"LW6010""甘农3号""甘农7号"和"陇东苜蓿"），设2个氮水平（210 mg·L^-1和21 mg·L^-1），以研究其在各生育期的生长特性、根系特性、结瘤特性、氮代谢酶活性及氮积累量。结果表明：随着生育期的推进，生长特性、根系特性和氮积累量在成熟期达到最大，结瘤特性在结荚期达到最大，氮代谢酶活性在盛花期达到最大；低氮处理，"LW6010"和"甘农7号"的生长特性、根系特性、结瘤特性、酶活性及氮积累量高于"甘农3号"和"陇东苜蓿"；高氮处理，"LW6010"和"甘农3号"的生长特性、根系特性、结瘤特性、酶活性及氮积累量高于"甘农7号"和"陇东苜蓿"。综上，氮高效型紫花苜蓿品种"LW6010"对氮素的固定、吸收及转化能力高于氮低效型"陇东苜蓿"。

关键词: 紫花苜蓿, 氮效率, 生育期, 氮利用特征