亚热带地区不同种植年限果园土壤团聚体结构及有机碳、氮分布特征

研究不同种植年限果园土壤团聚体结构变化规律,探究各粒级团聚体有机碳、全氮分布变化特征,旨在为亚热带地区果园土壤肥力形成和变化规律等相关研究提供参考。以林地土壤(0 a)和不同种植年限(2、10、20、30 a)果园土壤为研究对象,分析种植年限与土壤团聚体结构及其有机碳和全氮含量的关系。结果表明:与林地土壤相比,开垦为果园后的土壤中2 mm团聚体含量显著增加;果园土壤团聚体含量随粒级减小而降低,其中2 mm和0.25～2 mm粒级分别占40.1%～64.9%和30.6%～46.4%;不同种植年限果园土壤各粒级团聚体含量无显著差异。各粒级团聚体有机碳和全氮含量随着种植年限的延长呈增加趋势,但C/N值呈下降趋势。相关分析表明,随种植年限延长而增加的土壤有机碳或全氮主要分布于0.25～2 mm粒级团聚体。亚热带地区林地开垦为果园可增加土壤大团聚体含量,但开垦为果园后种植年限对土壤团聚体各粒级的分布无显著影响。虽然随着种植年限延长可显著提高各粒径下有机质和全氮含量,但C/N降低,建议果园管理过程中应适当减施氮肥、增施有机肥,提高土壤养分有效性。

Characteristics of soil aggregate structure and organic carbon and nitrogen distribution in orchards of different planting age in subtropical areas

To investigate the relationship between planting age and soil aggregate structure as well as the distribution characteristics of organic carbon and nitrogen, soils from a woodland(0 a)and orchards of different planting age(2, 10, 20, 30 a)were collected and analyzed in this study. The results showed that the content of soil aggregates with size >2 mm increased after conversion from woodland to orchard. In orchard lands, the soil aggregate content decreased with its size and was dominated by the particle size classes of >2 mm and 0.25~2 mm, which were 40.1%~64.9% and 30.6%~46.4% of all size classes, respectively. However, there were no significant differences in soil aggregate structure among the different planting ages. The soil organic carbon and total nitrogen contents increased within each aggregate size class with planting age, whereas the C/N ratio decreased. The increased soil organic carbon and total nitrogen contents were mainly distributed in the soil aggregates with sizes of 0.25~2 mm. These results indicated that soil macroaggregate content(>2 mm)increased after conversion from woodland to orchard, whereas there were no significant differences among soils from orchards of different planting age. The contents of organic carbon and total nitrogen improved with planting age. However, the C/N ratio decreased and should be adjusted in orchards via reduced nitrogen fertilizer application and increased organic fertilizer application.