几种土壤剖面的硝化作用及其动力学特征

NITRIFICATION AND DYNAMICS IN PROFILES OF DIFFERENTLY MANAGED SOIL TYPES

摘要:

选用陕西省六种主要耕作土壤及其剖面不同层次23个土样,在实验室培养条件下,研究其硝化作用的特点,并选用dN/dt=bN(B-N)/B方程(式中,N为硝态氮的累积量,t为试验培养时间,B为硝态氮累积量的渐进值),描述硝化作用过程中硝态氮含量随时间的用积,获得定量描述硝化作用强弱的两个指标(K_mx和t_d).结果表明耕层土壤由北向南硝化作用强度逐渐减弱,硝化作用的最大速率(K_mx)变幅为2.70～16.58mg/kg·d,陕北的黑垆土硝化作用进行最快,陕南的黄泥巴最慢。在不同土壤剖面中,硝化作用由上到下呈现减弱趋势,硝化作用的最大速率(K_mx)随上层深度增加而下降,迟缓期(t_d)随土层深度增加而延长,在粘化层和粘重土层中、硝化作用非常微弱或基本不发生硝化作用。这些不同土壤及剖面层次硝化作用的差异与土壤的物理、化学特性有关。

Abstract:

The 23 soil samples including the 6 types of managed soils were collected different regions in Shanxi Province for this research project The change of nitrate nitrogen accumulation with time was detemvned during the process of nitrification. The equation, dN/dt=bN(B-N)/B(N is the amount of NO₃^-N accumulation, t is time of incubation, and B is the asymptotic value of NO₃^-N, depending on the amount of NH₄-N added to the soil), was used to represent the accumulation of nitrate nitrogen with time. The maximal rate of nitrification (K_mx) and the delayed period (t_d) were derived from the equation and used to characterize quantitatively the nitrification process in various soil samples. The K_mx and t_d of surface soil samples were from 2.7 to 16.58 mg/kg·d and from 1.3-3.5d, respectively. The K_mx decreased and t_d increased with soil depth. Some soil properties affected the rate parameters.