亚热带土壤团聚体测定方法的比较研究

Comparative Studies on Measurement Methods for Aggregate Stability of Subtropical Soils

应用湿筛法、Emerson法、机械和化学分散法、LeBissonnaia法对亚热带第四纪红土发育的富铁土团聚体组成和稳定性进行评价,土壤团聚体数量和稳定性指标分别用>0.25mm水稳性团聚体含量(WSA)、团聚体平均重量直径(MWD)和团聚体破坏率(PAD)表示。结果表明,3种方法测定的MWD值呈极显著正相关;土壤团聚体数量和稳定性与土地利用方式密切相关,林地和园地较高,荒地和母质最低;5～2、2～1和1～0.5mm团聚体经快速湿润(FW)、慢速湿润(SW)和预湿后扰动(WS)处理后,团聚体MWD均表现为WS>SW>FW,相对消散系数(RSI)为31%～45%,表明团聚体崩解的主要物理机制是团聚体中闭塞空气引起的消散作用。3种方法具有可比性,反映土壤团聚体特性和稳定机制,可将其团聚体数量和稳定性指标作为衡量土壤质量和抗蚀性的重要指标。

The aggregate size distribution （ASD） and aggregate stability of subtropical soils developed on Quaternary red clay were measured by routine wet- sieving, Emerson modified method, mechanical shaking and chemical dispersion, and Le Bissonnais method. The amount and stability of aggregates were assessed by using the indices such as： 0.25 mm water- stable aggregate （WSA）, aggregate mean weight diameter （MWD） and percentage of aggregate destruction （PAD）. Results showed that amount of 0.25 mm WSA determined by the wet- sieving method were highly significantly correlated with the MWD values determined by the dispersion and Le Bissonnais methods. The MWD of the soils was closely related each other among three methods. When ranking soils according to MWD, forest and fruit soils showed higher MWD values than that of the other soils. The bare soil and soil- forming parent material had the lowest stability indices of aggregates. When ranking according to MWD in the three treatments of Le Bissonnais method, the order was WSSWFW, indicating that the major processes of aggregate breakdown in subtropical soils was caused by the compression of air entrapped inside aggregate during wetting. It occurred when dry aggregates were immersed in water or rapidly wetted. The amount and stability indices of aggregate determined by three methods were correlated and observed the same trend for aggregate properties of soils, which could be taken as indicators for soil quality and soil antierodibilty.