Micromorphological Characteristics Of Long-term Sewage Irrigation Farming Soil

Using the data obtained from micromorphology under the different irrigation,this paper attempts to study the soil micromorphologieal characteristics on different irrigation and research the telation of soil micromorphology and irrigation mode and accurate interpretation of micromorphology to land management for the sustainable use of soil resources to provide some basis. This paper chooses cultivated soils under sewage(LJZ) and normal(LSH) irrigation in northern Xi'an city as research objects.The paper uses the Leica—DMRX polarizing microscope to observe, analyse and describe the soil micromorphological characteristics and spatial and temporal distribution(including coarse grains characteristics and minerals assemblage,voids characteristics, microstructure,the pedofeature,etc.).High resolution digital images about typical micromorphology are colletted by ACT-1 and seamless splicing.Using SISC IAS VS.0 analyzes and measures soil micromorphological characteristics(including the length of the coarse grains,width,elongation, roundness,perimeter,area,eqdiameter,orientation and roughness,etc.).Bisides,the paper analyzes physical and chemical properties(including pH,CaCO₃,TOC,particle size,moisture,bulk density, magnetic susceptibility,etc.).By analyzing a lot of first-hand datas,conclusions drawn in the study are as follows:(1) Long-term sewage irrigation has significantly effects to soil physical and chemical properties,soil secondary-clay,weathering degree about iron-manganese,voids morphography and the pore development.But has no obvious effect to minerals assemblage about coarse grains, secondary-calcite and pore types.(2) Long-term sewage irrigation has significantly effects to soil physical and chemical properties.On the texture of soils,clay at the profile LJZ is significantly higher than at profile LSH, but silt is opposite.The profile LJZ about TOC is higher than LSH,particularly in 35-80cm outstanding.The profile LJZ about bulk density is higher than LSH,particularly in 40-80cm outstanding.The profile LJZ about water is higher than LSH.(3) Long-term sewage irrigation has no obvious effect to minerals assemblage about coarse grains.The minerals assemblage is very similar at profile LJZ and LSH.It is mainly composed of Quartz and Plagioclase and is occasionally composed of Hornblende,Mica,Eepidote,Opacite and so on.However,long-term sewage irrigation has effects to different relative proportion about minerals.(4) Comparison between the profile LJZ and LSH,long-term sewage irrigation has no obvious effect to the change of direction and degree about coarse particles at the Ap Horizon.Coarse(＞10μm) morphology is very similar and changes of index parameters including the length,width, roundness,eqdiameter,etc.is less.But has obvious effects to the change of degree about coarse particles at the B Horizon and changes of each index parameters is larger.It mainly shows parameters at the profile LJZ is larger than at the profile LSH.(5) Long-term sewage irrigation has obvious effects to morphology,quantity and spatial position about secondary-clay.Besides residual clay,there is also illuvial clay at profile LJZ,but there is some disseminated residual clay at profile LSH.Long-term sewage irrigation has on obvious effect to secondary-calcite,only there are some differences in abundances.But has obvious effects to weathering degree about iron-manganese.(6) Long-term sewage irrigation has on obvious effect to voids morphography.There are mainly composed of filling-pore,holes and channels microstructures the Ap Horizon at profile LSH and LJZ. Pore shapes are very complex,which are coarse and more regular pore and fine and irregular pore coexist.Long-term sewage irrigation has obvious effects to forms about viods and the pore development.The voids at profile LJZ have more regular and more smooth void walls comparatively, while at profile LSH the voids are more rough void walls.As far as the pore development,at profile LSH is higher at profile LJZ.The former is fine and density,the latter is large,multiple and loose. The B horizons in both profiles are characterized by the presence of a large amount of small irregular voids with rough void walls.