南亚热带不同母质发育土壤团聚体特征及其稳定性

团聚体是土壤的基本结构单位,其稳定性是评价土壤质量的重要指标。以南亚热带地区不同母质(石灰岩、第四纪红黏土、砂页岩)发育的土壤作为研究对象,采用湿筛法和LB法测定不同母质发育土壤团聚体稳定性特征。结果表明:(1)随着土层深度的增加,土壤容重呈上升趋势,而孔隙度、有机质和游离氧化铁含量呈下降趋势。砂页岩母质发育的土壤有机质含量最高,为22.44～42.97 g/kg。石灰岩和第四纪红黏土母质发育的土壤以黏粒(40.93%,42.51%)和粉粒(41.69%,42.31%)为主,砂页岩母质发育的土壤黏粒含量最低,为33.79%。(2)经湿筛法处理后,石灰岩母质发育土壤水稳性团聚体含量为91.58%～92.31%,第四纪红黏土母质发育土壤水稳性团聚体含量为76.45%～90.80%,砂页岩母质发育土壤水稳性团聚体含量为79.18%～86.67%,3种土壤团聚体的稳定性都随着土层深度增加而降低。(3)LB法处理后土壤团聚体MWD值均表现为慢速湿润处理预湿润振荡处理快速湿润处理,砂页岩母质发育的40—60 cm土层对消散和机械破碎作用最为敏感,其相对消散指数RSI和相对机械破碎指数RMI分别为0.78和0.42。不同母质土壤团聚体稳定性均与黏粒、有机质、游离态铁含量呈正相关。

Characteristics and Stability of Soil Aggregates Developed from Different Parent Materials in the South Subtropical Region

Aggregate is the basic structural unit of soil, and its stability is an important index to evaluate soil quality. In this paper, the stability of soil aggregates developed from different parent materials (Limestone, Quaternary laterite, Sand shale) in the south subtropical region was determined by wet-sieving method and Le bissonnais method. The results showed that:(1) With the increase of soil depth, soil bulk density increased gradually, while porosity, organic matter and free iron oxide content decreased. The highest content of organic matter was 22.44~42.97 g/kg. The clay (40.93% and 42.51%) and silt (41.69% and 42.31%) were the main parent materials of Limestone soil and Quaternary laterite soil, while clay content of Sand shale soil was the lowest, 33.79%. (2) After wet-sieving, the contents of water stable aggregates in Limestone soil, Quaternary Red soil and Sand Shale soil were 91.58%~92.31%, 76.45%~90.80%, and 79.18%~86.67%, respectively. The stability of aggregates in soils decreased with the increase of soil depth. (3) The MWD values of soil aggregates of the three parent materials were slow-wetting treatment > pre-wetting shock treatment > rapid-wetting treatment, The 40-60 cm soil layer developed from Sand shale was most sensitive to dissipation and mechanical crushing, and its relative dissipation index RSI and relative mechanical crushing index RMI were 0.78 and 0.42, respectively. The stability of soil aggregates was positively correlated with clay, organic matter and free iron content.