施氮水平对基础肥力不同的玉米田土壤有机碳组分数量的影响

Effect of Nitrogen Applied Levels on the Amounts of Organic C Components from Corn Field Soils with Different Basic Fertilities

以玉米长期定位施肥试验地为供试对象,采用化学分析法,比较不同施氮水平（不施氮、70%×优化施氮、优化施氮、130%×优化施氮和农民习惯性施氮）对不同肥力土壤0-20 cm耕层有机碳组分数量的差异影响。结果表明,施氮水平对高、中、低3种基础肥力土壤有机碳（SOC）含量的影响规律不同,在低肥力区域,较高施氮水平会加剧土壤退化;适宜氮素用量（0-240 kg/hm2）更有利于高肥力土壤易氧化有机碳（ROC）的积累。低肥力土壤难氧化有机碳（DOC）抵御外源氮素干扰的能力较差,施氮能加速该组分的矿化,大幅降低SOC的氧化稳定性,不利于肥力保蓄;施氮可同时减少高肥力地块轻组有机碳、重组有机碳的含量,优化施氮更有利于SOC的年轻化,使其活性增高。在中、低肥力区域,重组有机碳均呈先增后减的规律变化,低肥力更有利于其含量的提升。

The method of chemical analysis was adopt to compare the differenc systematically among the ef-fects of different N applied levels（no N, 70%×optimized N, optimized N, 130%×optimized N, habitual N of ordinaryfarmers） on the amounts of organic C components in the farmland surface soil（0-20 cm） with different basic fertili-ties. The results showed that, the influenced rules of N levels applied in the soils with three different basic fertilitieson their soil organic C（SOC） contents were different. In the area with low fertility, the increasing level of N applica-tion could speed up the trend of soil degeneration. The appropriate scope of N in the range of 0-240 kg/ha could in-crease the amount of readily oxidizable organic C（ROC） of soil with high fertility. The ability of difficultly oxidizableorganic C（DOC） from the low fertility soil resisting the exogenous N interference was poor. The N application couldaccelerate the mineralization of DOC and then reduce the oxidation stability of SOC greatly, which was negative forthe soil fertility maintenance. The N application could reduce the organic C contents of light and heavy fractions si-multaneously, the optimized N application could make the SOC of plot with high fertility newer and the activity en-hanced. In the soils with medium and low fertility, both of the organic C in the heavy fractions experienced a similarrule that DOC was increased first and then decreased, in which the N application was more helpful to accumulatethe DOC contents of low fertility soil.