NO_3^--N/NH_4^+-N混合氮不同水平对紫花苜蓿生长特性的影响

Effects of different levels of NO_3^--N/NH_4^+-N mixed nitrogen on growth characteristics of Medicago sativa L.

以甘农3号为研究材料,采用室外防雨网室盆栽营养液砂培法,以混合氮NO_3^--N:NH_4^+-N1:1为氮源,研究了5个供氮水平0、105、210、315、420 mg/L对紫花苜蓿苗期、现蕾期和盛花期地上部分及根系生长特性的影响。研究表明:NO_3^--N/NH_4^+-N混合氮能够促进紫花苜蓿根系和地上部分的生长发育,氮素浓度为315 mg/L最能促进地上部分的生长发育,该浓度下,与对照相比,株高和地上生物量最高可分别增大169.39%和333%。根系的最适浓度在氮素浓度210 mg/L,根重、根长和根尖数最高可分别增大570.83%,161.79%和343.82%。NO_3^--N/NH_4^+-N混合氮素浓度105 mg/L处理对紫花苜蓿根系生长和株高的促进作用高于氮素浓度420 mg/L处理,对地上生物量累积的促进作用则相反。苗期供氮主要促进根系的生长发育,现蕾期供氮主要促进株高和生物量的累积。因此,对紫花苜蓿生长最适NO_3^--N/NH_4^+-N混合氮浓度为210 mg/L。

Choosing Medicago sativa L.Gannong No.3 as the material,this experiment was conducted to study the effect of five kinds of nitrogen levels（0,105,210,315,420 mg/L）of mixed nitrogen（NO_3^--N：NH_4~＋-N=1：1）on the growth characteristics of root and overground parts of Medicago sativa L.during its seedling stage,squaring stage and full-bloom stage by the method of outdoor（rain-proof screenhouse） potting nutrient solution sand culture.The result shows that NO_3^--N/NH_4~＋-N mixed nitrogen application could promote the growth and development of root and overground parts of Medicago sativa L.The concen-tration of mixed nitrogen which can facilitate the growth of overground parts the most is 315 mg/L,At this concentration,the highest of the plant height and aboveground biomass were increase of 169.39%and 333%than the CK,and 210 mg/L was the optimum mixed nitrogen concentration of root growth,the root weight,length and tips increased by570.83%,161.79%and 343.82%,repectively.The promote role of mixed nitrogen concentration 105 mg/L on root growth and the plant height of alfalfa were higher than that of 420 mg/L;the ground biomass was on the contrary.Nitrogen mainly promotes root growth in seedling and promotes the plant height and biomass accumulation in bud stage.It is suggested that the optimum mixed nitrogen concentration is 210 mg/L.