外源供氮水平对大豆生物固氮效率的影响

Biological Nitrogen Fixation Efficiency in Soybean under Different Levels of Nitrogen Supply

采用稳定性同位素15N自然丰度（15N natural abundance）技术,以小麦为参照植物,研究了盆栽条件下,在外源供氮0、0.8、2.0、4.0 mmol·L^-1水平下大豆的生物固氮百分率以及生物固氮数量对植物氮的贡献.结果显示：（1）0-2.0 mmol·L^-1外源供氮可显著提高大豆的生物量和固氮百分率,且于2.0 mmol·L^-1处理下地上生物量最高,达104 g·m^-2,比CK增加了48%;（2）在0.8 mmol·L^-1的供氮水平下大豆生物固氮量最高,为1.318 g·m^-2,占大豆植株总吸氮量的70.4%,而在4.0 mmol·L^-1供氮水平下生物固氮量仅占植株总吸氮量的44%;随供氮水平的升高,大豆生物固氮量占总吸氮量的比重下降,说明在高水平外源氮下,大豆生物固氮能力受到抑制;（3）大豆生物固氮百分率、固氮数量及吸氮数量与地上生物量间均呈显著正相关关系.结果表明,应用稳定性15N同位素技术可以定量大豆的生物固氮效率,根瘤菌接种配合低浓度外源氮有利于大豆生物固氮潜能的释放,对提高大豆产量、减少化肥投入有积极的指导意义.

A pot experiment was conducted to determine the BNF （biological nitrogen fixation） ability of soybean [Glycinemax （Linn.） Merr.] under 0,0.8,2.0,4.0 mmol N · L^-1 levels nitrogen supply. The percentage nitrogen fixation rate （% Ndfa） was tested by MAS isotope spectrometer. Spring wheat was used as reference plant. The results showed that soybean biomass was significantly increased with the supplied N level at range 0 to 2.0 mmol · L^-1. The aboveground biomass at 2.0 mmol · L^-1 nitrogen supplied was up to 104 g · m^-2 ,48% increase than that of CK;The N2 fixation amount in soybean was the highest when the supplied N concentration was at 0.8 mmol · L^- 1 ,some 1. 318 g · m^-2 was fixed, amounted to 70% of total soybean N uptake,BNF ability was shown to be restricted at supplied N levels above 4.0 mmol · L^-1. Significantly positive linear relationships among % Ndfa, amount of N fixed, plant N uptake and aboveground biomass were found. It conclude that N2 fixation amount in soybean can be assessed using 1aN natural abundance method,the BNF ability was weaken when additional N supply increased.