常规与有机农田土壤团聚体组成及碳氮储量研究

长期施用化肥或连作农田管理模式导致土壤质量退化及碳氮损失加剧。以常规农作大豆和转换后的有机农作大豆田土壤为研究对象，利用土壤物理分组技术，分析了土壤团聚体组成及碳氮储量变化。结果表明，常规农作大豆田转换为有机农作大豆田后，<0.053mm粉粒加黏粒比重显著降低，0.053~0.25mm较小团聚体显著增加，土壤稳定性增大，土壤及团聚体中有机碳和全氮含量都显著增加。有机农作大豆田土壤包被于较小的大团聚体(0.25~2mm)中的<0.053mm细颗粒有机质百分比显著降低，0.053~2mm粗颗粒有机质显著增加。有机农作大豆田土壤及团聚体中碳氮储量都显著高于常规农作大豆田，土壤碳汇和氮汇效应增大。有机农作大豆田土壤稳定性增加，团聚体中碳氮含量显著增加，土壤碳汇效应增强，有机农作方式可能比常规农作方式更有利于土壤碳氮资源持续利用。

Soil Aggregate Composition and Carbon and Nitrogen Storage in Conventional and Organic Farmlands

Longterm mineral fertilizer input or crop monoculture management can result in soil quality degralotion and soil carbon and nitrogen depletion.This study focused on soil physical properties during the conversion from conventional farming to organic farming of soybean field.Soil aggregate composition and carbon and nitrogen storage were analyzed by using soil physical aggregate isolation method. Results showed that<0.053 mm aggregate fraction and soil organic carbon content of<0.053 mm aggregate in microaggregates occluded water-stable macroaggregates decreased,while 0.053-0.25 mm aggregate fraction and soil organic carbon content of 0.053-2 mm in microaggregates-occluded water-stable macroaggregates increased significandy after the conversion from conventional soybean field to organic soybean field.Higher aggregate stability and carbon and nitrogen storage were detected in organic farming system.Organic farming is better than conventional farming ecosystems in conserving soil fertility and system stability.