Soil Aggregate Stability And Influencing Factors Under Different Land Uses In Guangdong Province

Soil aggregate is the basic unit of soil structure,and its stability is an important indicator to evaluate soil fertility.It is of great significance to reveal the influencing factors of soil aggregate stability for guiding soil management.In this paper,the topsoil of forest land,paddy field and upland derived from Quaternary red earth,sand shale and granite was collected in Guangdong Province.The distribution of different size aggregates in soil was measured,the content of organic carbon and its fractions,free iron,crystal iron,complex iron and amorphous iron in soil aggregates were analyzed,and the aggregate stabilities in soils under different land uses were evaluated.The dominated factors affecting soil aggregate stability were analyzed by principal component analysis and multiple stepwise regression.The main results are as follows:(1)The soil aggregate was dominated by > 2mm aggregate in forest land,accounting for 43.1% ～ 80.0%;and dominated by 2-0.25 mm aggregate in paddy field and upland,accounting for 33.2% ～ 65.2% and 50.3% ～ 62.4% respectively.Mean weight diameter(MWD)and geometric mean diameter(GMD)of aggregates in soils derived from the Quaternary red earth and sand shale were in the order of forest land > paddy field > upland,and in soil derived from granite was in the order of forest land > upland > paddy field,the soil aggregates stability of forest land was the highest.(2)The contents of organic carbon,humus,humic acid and fulvic acid in soil were in the order of forest land > paddy field > upland.The organic carbon,humus,humic acid and fulvic acid in forest soil was the highest in >0.25 mm aggregates,and was the highest in <0.25 mm aggregates in paddy field and upland derived from Quaternary red earth and sand shale.The content of organic carbon,humus and humic acid in forest soil was the highest in >2mm aggregates,and was the highest in <0.053 mm aggregate in paddy field and upland derived from granite.(3)The content of free iron,crystal iron and complex iron in forest soil was significantly higher than those in paddy and upland soil.The free iron,crystal iron and complex iron of soil aggregate are mainly concentrated in <0.053 mm aggregate.The amorphous iron in forest soil was mainly concentrated in >0.25 mm aggregate,and mainly concentrated in <0.053 mm aggregate in paddy field and upland.(4)Soil organic carbon,humus,humic acid,fulvic acid,free iron,crystal iron,complex iron were significant correlated with index of soil aggregate stability(MWD,GMD),and Fulvic acid contributed the most to soil aggregate stability;organic carbon,humus,humic acid,fulvic acid,free iron,crystal iron,complex iron in >2mm aggregates were significantly correlated with MWD and GMD,which affected soil aggregate stability...