施氮对不同水分条件下紫花苜蓿氮素吸收及根系固氮酶活性的影响

doi:10.11686/cyxb2019268

摘要/Abstract

摘要： 氮肥施用可以调控不同水分条件下紫花苜蓿的生长,而其内在机制尚不明确。采用盆栽试验,通过设置3个水分梯度(田间最大持水量的30%、50%以及70%,分别用W₁、W₂、W₃表示)及4个氮素水平(0、0.02、0.04、0.06 g·kg^-1,分别用N₁、N₂、N₃、N₄表示),研究了不同水分条件下紫花苜蓿对氮素的需求规律及其与氮素吸收及根系固氮酶活性的关系。研究结果表明:1)W₁水分条件下,氮肥施用可以显著提高紫花苜蓿生物量,而在W₂及W₃水分条件下,均以N₃处理紫花苜蓿生物量最大;2)W₁及W₂水分条件下,N₄处理植株氮素积累量最高,而在W₃水分条件下,以N₃处理氮素吸收量最高,植株氮素积累量与生物量间存在显著正相关关系;3)根系固氮酶活性随土壤水分有效性的增加而增加,随氮素供应量的增加而降低,在N₄条件下,W₄处理固氮酶活性与W₃处理无显著性差异。因此,在低土壤水分条件下,氮素供应可以保证植株对氮素的需求并提高其生物量;在高土壤水分条件下,适宜供氮量可以促进紫花苜蓿的生长,但过高氮肥供应会显著抑制根系固氮酶活性并最终导致氮素吸收及生物量不再进一步增加。本研究结果可为紫花苜蓿生产系统中的水氮管理提供理论依据。

关键词: 紫花苜蓿, 氮肥施用, 土壤水分, 固氮酶活性, 氮素积累

Abstract: The underlying mechanisms related to the impact of nitrogen fertilizer on alfalfa (Medicago sativa) growth at different soil water contents remain unclear. A pot experiment with three soil water levels (30%, 50% and 70% of the field water-holding capacity; W₁, W₂ and W₃), and four nitrogen application rates (0, 0.02, 0.04 and 0.06 g N·kg^-1; N₁, N₂, N₃ and N₄) was conducted to study the utilization of nitrogen fertilizer by alfalfa under different soil water regimes, and the relationships with nitrogen accumulation and root nitrogenase activity. The results indicated that: 1) for W₁, alfalfa biomass increased significantly with increase in nitrogen application rate, while for W₂ and W₃, the highest biomass values were observed in N₃ treatment; 2) for W₁ and W₂, the highest nitrogen accumulation was obtained in the N₄ treatment, while for W₃, the N₃ treatment had the highest nitrogen accumulation. A positive relationship between the amount of nitrogen applied and alfalfa biomass was therefore concluded; 3) the root nitrogenase activity was increased with increase in soil water availability, but decreased with increase in nitrogen rate. No significant difference in root nitrogenase activity was observed between W₃ and W₄ with N₄ application. Therefore, it was concluded from these results that under lower soil water content, nitrogen application was essential for meeting nitrogen demand and would promote alfalfa growth, and under higher soil water content, moderate nitrogen fertilizer application was advantageous for alfalfa growth, while higher rates of nitrogen fertilizer application inhibited root nitrogenase activity, and therefore no significant differences in nitrogen accumulation and biomass were found. The results of the present study provide a theoretical basis for determining water and nitrogen management in alfalfa production systems.

Key words: alfalfa, nitrogen application, soil water, nitrogenase activity, nitrogen accumulation

高丽敏, 苏晶, 田倩, 沈益新. 施氮对不同水分条件下紫花苜蓿氮素吸收及根系固氮酶活性的影响[J]. 草业学报, 2020, 29(3): 130-136.

GAO Li-min, SU Jing, TIAN Qian, SHEN Yi-xin. Effects of nitrogen application on nitrogen accumulation and root nitrogenase activity in Medicago sativa at different soil water contents[J]. Acta Prataculturae Sinica, 2020, 29(3): 130-136.

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