不同NO_3^--N/NH_4^+-N配比对紫花苜蓿盛花期生长及结瘤固氮的影响

Effects of the ratios of NO_3^--N/NH_4^+-N on growth,nodulation and nitrogen-fixation of alfalfa at flowering stage

在完全营养液条件下,采用砂培法,研究了NO3--N与NH4+-N两种氮素形态的7种配比(氮素水平210mg/L)对紫花苜蓿盛花期生长及结瘤固氮的影响。结果表明:各形态配比下紫花苜蓿的株高、生物量、根瘤数、根瘤重及固氮酶活性均随NO3--N/NH4+-N增大呈先增大后减小的趋势;且NO3--N/NH4+-N比例为5/3时,紫花苜蓿的株高、生物量、根瘤数、根瘤重及固氮酶活性均取得最大值,而地上部和地下部全氮含量则在5/5时最高。综合分析,当氮素水平在210mg/L时,5/3处理下紫花苜蓿生长较好,自身固氮能力较强。

Under the condition of complete nutrient solution,the effect of 7 ratios of NO3 --N/NH4 ＋-N （the nitrogen level was 210 mg/L）on growth,nodulation and nitrogen-fixation of alfalfa were studied at flowering stage by sand culture method.The results showed that along with the increase of NO3 --N/NH 4 ＋-N ratio,plant height,biomass,nodule number,nodule weight and nitrogenase activity showed a trend of increasing first and then decreasing under different ratios of NO3 --N/NH 4 ＋-N.The plant height,biomass,nodule number,nodule weight and nitrogenase activity of alfalfa achieved the maximum at 5/3,while the total nitrogen content of aboveground and underground were highest at 5/5.Under the nitrogen level of 210 mg/L,alfalfa performed best under 5/3 treatment and the nitrogen-fixing ability was the strongest as well.