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.

Distribution of Soil Nitrification within Soil Aggregates and the Effects of Tillage on It