Organic matters improve the physical, chemical and biological properties of soil, influence soil structure by binding mineral particles, while cultivation is an important factor influencing the content of soil organic matters. Also soil aggregates are important indicators of soil physical quality, reflecting the impact of land use and management. This study, by selecting five sampling plots with different cultivation age, was conducted to exmine the effects of conventional cultivation on soil organic carbon and aggregates in the semiarid Loess Plateau in China. The results showed that the content of water-stable macroaggregates ( ≥0.25 mm) decreased by 40.5% and 12.5% in the layers of 0 ~ 20 cm and 0 ~ 40 cm after > 70 years reclamation, respectively. Aggregates could be broken typically by reclamation. The average values of MWD and GMD in 0 ~ 20 cm were nearly 10% higher than in 20 ~ 40 cm layer, and the difference decreased with cultivation time. Organic carbon contents of > 2 mm and 0.25 ~ 0.106 mm water-stable aggregates were much higher in 0～20 cm layer, while it was not obvious in 20 ~ 40 cm layer, carbon contents of water-stable aggregates for the whole soil profiles decreased generally with cultivation time. The favorable correlation of MWD and GMD with organic carbon in soil aggregates indicated that aggregates could protect soil organic carbon from erosion.%通过野外调查取样,并结合室内实验分析,对甘肃会宁县丘陵地区不同耕作年限黄绵土耕地不同土层(0～ 20 cm,20～40 cm)土壤团聚体分布及稳定性和水稳性团聚体有机碳含量进行研究.结果表明:未经开垦土壤团聚体稳定性最好,耕作明显地破坏土壤团聚体,降低其稳定性;经过70 a以上时间开垦,0～ 20 cm和20～40 cm土层≥0.25 mm直径水稳性团聚体含量分别下降了40.5％和12.5％.耕作层水稳性团聚体平均重量直径和几何均重直径比亚表层平均大了10％,两土层之间的差异随着耕作年限变小.0～20 cm土层,＞2mm和0.25～0.106mm直径水稳性团聚体有机碳含量较高;20 ～ 40 cm土壤各直径水稳性团聚体有机碳含量差异不明显,耕作层以及亚表层水稳性团聚体有机碳含量整体表现出不断下降的趋势.平均重量直径和几何均重直径与土壤有机碳之间很好的相关性表明团聚体对于有机碳的保持作用关键.
展开▼
