水保所知识产出(1956---)知识库

以黄土高原连续进行了 27 年的长期定位试验为对象，研究了粮-草长周期轮作、粮-豆短周期轮作、玉米连作和小麦连作
系统土壤团聚体及其碳氮分布特征，并分析了土壤碳氮分布与土壤团聚体及其碳氮含量之间的关系。结果表明：黄土高原旱作农田
土壤中<0.053 mm 团聚体含量最高，占土壤质量的 35%；长周期轮作系统 0~20 cm 和 20~40 cm 土层土壤 0.25~2 mm 团聚体含量高
于玉米连作、小麦连作和短周期轮作系统，而<0.053 mm 团聚体含量低于这 3 种轮作系统，且长周期轮作系统土壤团聚体的平均重
量直径和几何平均直径也较高。种植系统对团聚体有机碳和全氮分布的影响主要体现在 0~20 cm 土层土壤，长周期轮作系统土壤
中>2 mm 和 0.25~2 mm 团聚体有机碳含量显著高于其他种植系统，<0.25 mm 团聚体有机碳含量与其他种植系统差异不显著。长周
期轮作系统团聚体全氮含量均显著高于其他种植系统，碳氮比则呈现出相反的趋势。土壤总有机碳、氮含量与团聚体有机碳、氮含
量呈极显著正相关关系。土壤有机碳和全氮含量的变化主要取决于 0.25~2 mm 和 0.053~0.25 mm 团聚体有机碳和全氮的变化，而
且有豆科植物苜蓿长期参与的长周期轮作系统可以有效改善土壤结构，提高土壤和团聚体的有机碳和全氮含量。

In this paper, we examined the distribution of water stable aggregates and organic carbon（OC）and nitrogen（N）in soils under
different cropping systems, using a 27-year field experiment in the Loess Plateau. The relationships between OC and N contents in bulk soil
and aggregates were also analyzed. Results showed that <0.053 mm aggregates, accounting for 35%, dominated the soil mass in 0~20 and
20~40 cm soil layers in the semiarid farmland of the Loess Plateau. The percentage of 0.25~2 mm aggregates was higher, but that of <0.053
mm aggregates was lower in the grass-grain rotation system than the other cropping systems. In the grass-grain rotation system, mean weight
diameter and geometrical mean diameter of soil aggregates were also greater. The significant effects of cropping system on OC and N associ－
ated with aggregates mainly occurred in 0~20 cm layer. The OC content in >2 mm and 0.25~2 mm aggregates was significantly higher in
grass-grain rotation system than in the other systems, while OC content in 0.053~0.25 mm and <0.053 mm aggregates did not differ among  different cropping systems. The grass-grain system showed higher N content and lower C/N ratio in each aggregate compared with other sys－
tems. The OC and N content in bulk soils was positively correlated with OC and N content associated with aggregates. These results suggest
that the responses of OC and N in the bulk soil to cropping systems mainly depend on OC and N associated with 0.25~2 mm and 0.053~
0.25 mm aggregates. Additionally, grass-grain rotation system has greater potential to improve soil structure and increase the content of OC
and N associated with aggregates.