土壤氮激发效应及其微生物机理研究进展

土壤氮激发效应是土壤养分释放、植物养分吸收过程中的关键机制。对土壤氮素激发的深入了解,不仅有助于农业生产上更加合理制定氮肥运筹,从而提高氮肥的利用率,也有利于评估和控制环境污染并提供有效的治污方法。本文在介绍土壤氮素激发效应概念和机制的基础上,评估目前土壤氮素激发效应的主流测定方法及其在实际应用中的优劣,重点阐述了外源添加物(无机氮肥、有机物料和根系分泌物)对土壤氮素激发效应的作用效果及其微生物机理。土壤氮激发模式中,外源添加物对土壤C/N比的影响可能是土壤氮激发效应作用的关键。当系统中有效C冗余时,施用无机氮肥,促进土壤有机氮的分解,从而表现正的激发效应;反之,有效C不足但有效N富集时,则表现为固氮微生物活性相对增强,从而出现负的激发效应。微生物是激发效应的推动者。本文通过共代谢理论、微生物热区理论和微生物能量与物质转化理论三个理论假说解析了微生物在土壤氮激发过程中可能的作用机制,从而深化对激发效应的认识,为进一步明确土壤激发效应的微生物机制、因素之间的互作效应及通过激发效应为提高氮肥利用效率提供有效途径。

Research Progress of Soil Nitrogen Priming Effect and Its Microbial Mechanisms

The soil nitrogen priming effect is the key mechanism in the process of soil nutrient release and plant nutrient absorption. The insight into soil priming effect will not only help make more reasonable nitrogen fertilizer operations in agricultural production, thus improving the utilization rate of nitrogen fertilizer, but also conduces to the assessment and control of environmental pollution, so as to provide effective pollution control methods. On the basis of the introduction of the concept and mechanism of soil nitrogen priming effect, we introduce the prevailing determination methods of the current nitrogen priming effect and its advantages and disadvantages of practical application. The effects of exogenous additives (inorganic nitrogen fertilizer, organic materials and root exudates) on soil nitrogen stimulation and their microbial mechanisms were emphatically expounded. The effect of exogenous additives on soil C/N ratio may be the key factor to soil nitrogen stimulation. When available C is redundant, the application of inorganic nitrogen fertilizer promotes the decomposition of soil organic nitrogen, thus showing a positive priming effect. On the contrary, when available C is insufficient but available N is enriched, the activity of nitrogen-fixing microorganisms is relatively enhanced, which results in a negative priming effect. Microorganisms are the promoters of priming effects. We also analyzed the possible mechanism of microorganisms in the process of soil nitrogen stimulation through three theoretical hypotheses: 1) co-metabolism theory; 2) microbial hotspots; 3) microbial energy and material transformation theory. Through the discussion, we can deepen the understanding of the priming effect, and provide an effective way to further clarify the microbial mechanism of the soil priming effect, the interaction effect between factors and the improvement of nitrogen use efficiency through the priming effect.