不同NH_4~+-N和NO_3~-—N水平对大豆苗期生长的影响

试验以东农47为材料,利用砂培方法研究了不同NH4+-N和NO3--N水平对大豆苗期生长的影响。结果表明,大豆总生物量和地上部生物量随氮素水平增加呈单峰曲线,NH4+-N水平对大豆苗期生长影响大于NO3--N。以NH4+-N做为氮源时,氮素浓度125 mg·L-1时总生物量和地上部生物量达最大值;以NO3--N做为氮源,氮素浓度在275 mg·L-1时总生物量、地上部生物量较高,500 mg.L-1时较低。氮素浓度大于20 mg·L-1时,以NH4+-N做为氮源总生物量、地上部生物量明显大于以NO3--N为氮源。氮素水平对苗期根系生物量影响不大,当氮素浓度为500 mg·L-1时,两种氮素形态根系生物量均较低,其它水平之间相差不大。根冠比随氮素浓度的增大呈降低趋势,当氮素浓度高于125 mg·L-1时根冠比变化较小。当氮素浓度为20 mg.L-1时,两种氮素形态之间根冠比没有明显差异,当氮素浓度大于20 mg·L-1时,以NO3--N做为氮源根冠比明显大于NH4+-N。

Effects of NH4+-N and NO3-N levels on growth of soybean in seedling stage

This work was conducted using DN47 which was cultivated by sand culture to study the effects of NH4+-N and NO3-—N levels on the growth of soybean at seedling stage.The results were shown as follows: total biomass and the shoot biomass changed with the increase of the nitrogen level and showed a sigle peak curve,the effect of NH4+-N was more than that of NO3-—N.Total biomass and the shoot biomass reached the peak when the concentration of NH4+-N was 125 mg·L-1,reached another peak when the concentration of NO3-—N was 275 mg·L-1,lowered when it was 500 mg·L-1,total biomass and the shoot biomass of NH4+-N were bigger than that of NO3-—N when the nitrogen concentration was above 20 mg·L-1.The biomass of root was lower when the nitrogen con-centration of two nitrogen forms were 500 mg·L-1 than that of other concentration,and there was no significant difference between other nitrogen levels.The root/shoot ratio decreased with the increase of nitrogen level,and hardly changed when it was 125 mg·L-1.When the nitrogen concentration was 20 mg·L-1,the root/shoot ratio of two nitrogen forms was similar,but NO3-—N was bigger than that of NH4+-N when the nitrogen concentration was above 20 mg·L-1.