土壤硝化作用在团聚体中的分布以及耕作的影响

土壤团聚体是最重要的一种土壤结构体.在西南大学国家紫色土肥力定位监测点,研究了长期(18 a)垄作免耕和常规轮作两种不同耕作方式下,不同大小土壤团聚体中硝化细菌及硝化作用强度的分布模式.结果表明,不同团聚体中土壤硝化作用分布不同,耕作方式对其在团聚体中分布无明显影响.＞0.053 mm各粒级中,土壤硝化作用强度随团聚体粒径的减小而减小,而＜0.053 mm的粉砂与粘粒组分中也表现出较高强度;大团聚体(2.0～0.25 mm)中的硝化细菌数量明显高于微团聚体(0.25～0.023 mm),＜0.053 mm粒级硝化细菌也呈现出较高数量;团聚体中无机氮素(NH_4~+-N和NO_3~-N)和pH对土壤硝化作用影响较小,无明显相关规律.同时,垄作免耕有利于大团聚体形成,土壤结构好,且比常规轮作具有更强的硝化能力.

Abstract：

Soil aggregates are the most important structures of soil. This paper reports a study of the distribution patterns of nitrobacteria and nitrifying intensity in soil aggregates under conventional tillage (CT)and ridge tillage (RT) in an 18-year long- term field experiment. The result indicates that nitrification distribution patterns vary in different soil aggregates whereas tillage methods have no obvious effect on aggregates. For aggregates with a diameter ＞0. 053 mm, soil nitrifying capacity reduces with the reduction of the particle size, but the nitrification of silt and the clay (＜0. 053 mm) component is also fairly strong.The nitrobacteria content of large-sized aggregates (2.0～0. 25 mm) is higher than that of the microaggregates (0.25～0. 023 mm) and the number of nitrobacteria is also fairly great for the particle size ＜0. 053 mm. Nitrogen (NH_4~+-N and NO_3~--N) and pH have no significant influence on nitrification within aggregates and no distinct regularities can be detected. Ridging with no-tillage is advantageous to big aggregate formation, improves soil structure, and shows greater nitrification ability than convention tillage.