不同NH_4^+-N和NO_3^-—N水平对大豆苗期生长的影响

Effects of NH_4^+-N and NO_3^-—N levels on growth of soybean in seedling stage

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。

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 concentration 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 20mg·L^-1.