叶面施氮对棉花根系吸收硝态氮的影响

Effects of Foliar Nitrogen Applications on the Absorption of Nitrate Nitrogen by Cotton Roots

【目的】探讨叶面施用不同形态氮素的肥料对棉花根系吸收硝态氮及棉株生长的影响。【方法】采用营养液培养法,利用15N同位素示踪技术开展氮素吸收研究,设置叶面施用同等氮浓度的铵态氮、硝态氮和酰胺态氮及清水(对照)4个处理。【结果】叶面施氮处理6 d后,叶面施氮处理棉株地上部氮含量和整株氮含量显著高于对照;棉株地上部、根及整株氮素积累量以叶面施用铵态氮处理最高,但各处理间没有显著差异。同位素示踪结果显示,铵态氮处理棉株地上部和根系中15N积累量分别为0.794 mg·株-1和0.318 mg·株-1,高于对照和酰胺态氮处理,且显著高于硝态氮处理;叶面施氮后,铵态氮处理棉株积累通过根系吸收的氮素约为11.35mg·株-1,较对照吸收氮素效率约提升28.0%,酰胺态氮和硝态氮处理较对照分别降低9.5%和20.5%。但是叶面施氮类型没有影响棉株对根系吸收硝态氮的分配,各处理棉株地上部和根系中分配根系吸收氮素的比例约为7∶3。【结论】在本试验条件下,叶面施用铵态氮能够促进棉苗根系对硝态氮的吸收利用。

[Objective]The purpose of this study was to explore the effects of foliar nitrogen application on nitrate nitrogen uptake and cotton growth.[Method]The experiment was carried out using the 15N isotopic tracer technique in a greenhouse hydroponic culture experiment.Four foliar treatments were applied;ammonium nitrogen,nitrate nitrogen,amide nitrogen treatments(all with the same concentration of nitrogen applied),and a water control treatment.[Result]Compared to the water control treatment,the nitrogen contents of the cotton shoots and the whole plant were significantly higher in plants with foliar nitrogen treatments 6 d after application.The nitrogen accumulation in the shoots,roots,and total plants was higher with the ammonium nitrogen treatment,but there was no significant difference among treatments.The isotopic tracer results showed that 15N accumulation in the shoot and root was 0.794 mg·plant-1 and 0.318 mg·plant-1 with the ammonium nitrogen treatment,respectively.These values were higher than the 15N accumulation with the water control treatment and the amide nitrogen treatment and significantly higher than the nitrate treatment.After foliar application,the plant accumulation of nitrogen via root uptake was approximately 11.35 mg with the ammonium nitrogen treatment.Compared with the water control treatment,the nitrogen uptake efficiency increased by 28.0%with the ammonium nitrogen treatment and reduced by 9.5%and 20.5%with the amide nitrogen treatment and the nitrate treatment,respectively.The proportion of nitrogen from root uptake was about 7:3 between the shoots and the roots with each treatment,indicating that the form of foliar-applied nitrogen did not affect the distribution of nitrate nitrogen via root uptake.[Conclusion]Foliar application of ammonium nitrogen could,therefore,promote nitrate nitrogen uptake by cotton seedling roots.