旱地长期培肥土壤脲酶和碱性磷酸酶动力学及热力学特征研究

The dynamic and thermodynamic characteristics of soil reactions catalyzed by soil enzymes under long-term fertilization in Loess Plateau

研究了连续25年长期培肥试验条件下土壤脲酶和碱性磷酸酶酶促反应的动力学和热力学特征,从酶学角度揭示长期培肥的效应。结果表明,长期培肥增加了脲酶和碱性磷酸酶酶促反应的Vmax、Vmax/Km和k值;降低了Ea、△G、△H和△S值,说明培肥能提高酶促反应速度、减小活化自由能、加快土壤中物质的生物循环过程。酶促反应动力学参数和热力学参数与土壤性质相关分析表明,酶促反应动力学参数大多依赖于土壤化学性状,基于动力学参数的土壤肥力指标体系可评价土壤肥力水平,且U-Vmax、P-Km、P-Vmax可作为土壤肥力的重要指标。

Soil enzyme is a sensitive indicator of soil fertility condition. The dynamic and thermodynamic characteristics of soil enzymes can illustrate the enzyme catalyzed soil biochemical processes and explain the changing mechanisms of soil fertility. In this paper, the dynamic and thermodynamic parameters of soil reactions catalyzed by soil enzymes were analyzed for the soils under 25 years＇ continuous fertilization. The objective of this research was to reveal the effects of long-term fertilization on soil fertility from the aspects of soil enzymes. The results showed that long-term fertilization increased Vmax, Vmax/Km and k, but decreased Eα, △G, △H and △S, indicating that fertilization could improve the velocity of enzymatic reaction, decrease the free energy for activation, and therefore boost the cycling process of soil nitrogen and phosphorus. The correlation analysis between dynamic and thermodynamic parameters of enzymatic catalyzed reaction and soil properties suggested that dynamic and thermodynamic parameters of enzymatic catalyzed reaction mainly depended on soil chemical properties and the soil fertility evaluation index system based on dynamic and thermodynamic parameters could be used to evaluate soil fertility. The results from this study further implied that U-Vmax, P-Km and P-Vmax were important indices for the evaluation of soil fertility.