浙西丘陵区水田改旱后土壤团聚体组成与稳定性的变化

选择浙西低丘地区的黄筋泥田和红紫砂田2类土壤的水田与相应改旱不同年限的旱地、果园和茶园,比较研究了水田改旱后土壤团聚体组成及其稳定性的变化.结果表明,水田改旱后,土壤中＞5.00 mm和＞0.25 mm非水稳定性团聚体和水稳定性团聚体数量均呈现下降,土壤团聚体的水稳定性减弱,其中,水稳定性团聚体的下降比非水稳定性团聚体更为明显.水田改旱种植旱粮,土壤中＞5.00 mm和＞0.25 mm非稳定团聚体、水稳定性团聚体及团聚体的稳定呈持续下降;而当水田改旱种植果树和茶树时,初期土壤中＞5.00 mm和＞0.25 mm非稳定团聚体、水稳定性团聚体和团聚体的稳定呈明显下降,但随着时间的增加,其大团聚体逐渐恢复.改旱后土壤团聚体的变化与其有机碳和无定形氧化铁数量发生变化有关.

Changes in Composition and Stability of Soil Aggregates in Hilly Area of the Western Zhejiang after Conversion of Paddy Fields to Upland

A soil sequence with different history of land use were collected respectively from western Zhejiang Province for studying the changes in composition and stability of soil aggregates after transformation from paddy fields to upland,orchard,and tea garden.Two types of soils （paddy field on quaternary red soil and paddy field on red-purple sandstone soil）,each including four land-uses,were collected.The results showed that,several years after transformation from paddy fields to upland,contents of both mechanical stable and water-stable aggregates with sizes of ＞ 0.25 mm and ＞ 5.00 mm decreased,and stability of soil aggregates became weak.Among them,the decrease in water stability of aggregates was more obvious than that of the mechanical stability of aggregates.For planting upland crops after the transformation of paddy to dryland,contents of ＞ 0.25 mm,＞ 5.00 mm mechanical stable and water-stable aggregates and stability of soil aggregates were continuously decreased with time.For panting fruit tree or tea plants after the transformation of paddy to dryland,contents of ＞ 0.25 mm,＞ 5.00 mm mechanical stable and water-stable aggregates and stability of soil aggregates decreased at the early stage.However,stability of aggregates was restored with increasing time.The changes in composition and stability of soil aggregates after transformation from paddy fields to upland,orchard,and tea garden were related to alteration of organic and iron oxides of the soils.