Abstract:The distribution of soils in the Yangtze delta is significantly influenced by the land forming age and the effect of new-tectonic movement.according to characteristics of the new-tectonic movement,the Yangtze delta may be divided into eight regions together with their corresponding soils,the regions are shown as follows:Ⅰ.Strongly uplifted mountain area.young soils.Ⅱ.Weakly uplifted hilly area:typical red earth and yellow brown earth.Ⅲ.Relatively stable lower hilly area:meadow yellow brown earth,light meadow soils and red earth.Ⅳ.Subsided Tai-lake depression:hnmic bog soils.Ⅴ.Subsided margins of Tai-lake depression:light meadow soils.Ⅵ.Subsided northern coastal sandy spit area:light meadow soils.Ⅶ.Strongly subsided debouchure area:light meadow soils and meadow saline soils.Ⅷ.Strongly subsided Hangzhou Bay:no sail formed.

Abstract:Field trials and micro-plot experiments using ¹⁵N-labelled ammounium sulfate were conducted on a silty clay paddy soil developed on alluvial deposits of the Fiangzhou Bay.The eaperiaients with same design for the early rice and Iate rice were laid ont segarately.in the same field for comparative investigation.

Abstract:The soil particles of the "whitish harizon" in bleached paddys were separated into seven fractions (1-0.25,0.25-0.05,0.05-0.01,0.01-005,0.005-0.002,0.002-0.001 and<0.001mm).Chemical analysis showed that the sand fraction (1-0.05mm) in which there are "iron-manganese sands" contained less SiO₂ and Fe2O3 than the silt fraction (0.05-0.002mm).The sand fraction was characterized by its very high magnetic susceptibility.Its hygrosqopic coefficient was also higher than silt fraction by 3.5-4.0%.These features of the soil are different from those of the upland sails.This implies that in addition to SiO₂,other minerals may also be present in the sand fraction.Experimental results confirmed that it was pnly the clay fraction(<0.002 mm) which could exhibit plasticity and swelling properties.The plastic index and swelling capacity of the fine clay(<0.001 mm) were higher than those of the coarse clay (0.002-0.001 mm) by 2-3 times.The compressive strength of the silt fraction was very low (0.014-0.147 Kg/cm²),but its bulls density in water was greater (1.37-1.42g/cm²).Under waterlogged csondition the silt fraction settled down as a compacted layer.The settling and compacting of the "whitish horizon" might be mainly affected by the content of coarse silt (0.05-0.01mm) and the ratio between coarse silt and fine clay.It is considered that the eribical limits for a soil to exhibit settling and compacting properties are: coarse silt content ≥40%,ratio between coarse silt and fine clay content ≥2,and the organic matter content ≤2%.

Abstract:The present paper deals with formation and reelamation of tile-like crust-solonetz in semi-arid region of China.Main characteristics of tile-like crust-solonetz are given as follows:1.There are no plant except alkali tolerant plants on this soil.2.On the surface of this soil,there are tile-like crusts of 1-2 cm in depth ;and on the crust back,there are spongy structures.3.Total salt content of the soil is sot so high in all the profile,that of the surface soil is less than 0.5% and that of the subsoil is about 0.1%.Sodium carbonate and sodium bicarbonate are predominant in salt composition The pH of the entire soil profile is above 9 and ESP is higher thaw 20%.Soil survey and the modelling test in the laboratory has proved that there are two different ways by which the crest-solonetz is formed.Firstly,in the process of alternation of accumulation and desalination,the sodium ions enter the soil adsorptive complex in the salt-affected foil containing sodium salt.Secondly,the soil is alkalized with the accumulation of sodium-carbonate and bicarbonate in soil induced by the rising of the lowly mineralized ground water.

Abstract:The present article deals with the potentiometric titration curves,differential thermal curves of acid leached soil colloids from black soil,yellow cultivated loesaial soil and red earth,and from clay minerals including bentonite,illite and kaolinite.The magnitude of buffer capacity is affected by the structural types of clay minerals in the order of montmorillonite>illite>kaolinite.The buffer capacity of different soil colloids varies with the types of soil in the prder of black soil>clayey light colored meadow soil>yellow cultivated loessial soil>red earth,the sequence seems to be related to the composition of clay minerals.

Abstract:Stability constants of zinc-humic acid complexes separated from soils,compost,peat and weathered coals were determined by ion exchange equilibrium method.Humic substances studied varied markedly in average molecular weight,content of carboxyl and phenolic hydroxyl group,degree of dissociation of carboxyl group and aromaticity.The results showed that the stability constants of Zn-humic acid complexes varied with the different origins of the humic substances,with the highest logK of 7.85 for a weathered coal and the lowest value of 3.52 for the albic horizon of a albic brown forest soil.The log K was correlated significantly with the content of undissociated (Ar weakly dissociated) carboxyl group,but not with the content of total carbonyl group pr phenolic hydroxyl group,average molecular weight,or aromaticity of Mimic substances.

Abstract:The mineralogical composition of the sol colloids separated from black soil,loessial soil,yellow brown earth,red earth and laterite have been quantitatively analysed by the systematic method of Alexiades and Jackson.In order to have the determination of the mineralogical composition of soil colloid more suitable for the actual conditions of these soils,the analytical methods of kaolinite and illite have been modified.The content of kaolinite was determined by NH₄Cl retention measurement instead of selective dissolution analysis.For estimating the content of illite,5% of K₂O extracted by 1 N HNO₃ regarded as a parameter.The content of mica was calculated by means of 10% of the amount of total K₂O substracted K₂O extracted by 1 N HNO₃.The composition of the clay minerals of the five soils varies greatly.The highest content of montmorillonite is found in black soil,and it is getting decreased gradually from the north to the south.While the content of kaolinate tends to increase gradually from the north to the south.Vermiculite and transitional minerals of 14Å are found in the soils of subtropical China.

Abstract:Numerical classification and delimitation of eroded soils in Guyuan county,Ningxia autonomous region were studied by means of the principal components and stepwise discriminatory analysis based on the data from the field observation and nemerical coding.In this study,84 different eroded soil samples were collected and analysed and four important factors which Rnfluenced soil erpsion were used as variables for calculation.On the basis of grouping of intensities of the erosion factors,the intensity values for every eroded foil were used as observable values of the variables.Through stepwise discriminatory analysis,the types of 17 soils among 84 eroded soils are adjusted,furthermore the discriminatory equations are established.The key of eroded soil types is compiled based on the data calculated from the equations.The types of eroded soils can be discriminated and development tendency of soil erosion can be predicted with the add of the key.The study on eroded soils by means,of principal components reveals the relationship between eroded soil types and principal erosion factore;and on the basis of this study a delimitation scheme of eroded soil regions is suggested.

Abstract:Micromorphalogical characteristics of black soils,planosols and soda-solonchaks of various levels of fertility were investigated by means of structure analysis,optical microscopy and scanning electron microscopy.The results are summarized as fallows:1.With large amount of humic substances,black soils are well aggregated and highly stable in structure.The content of microaggregates(>0.05 mm) in black soils is about 30-70%,that in planosols is less than 30%,that in unimproved soda-solonchak is 20%,and that in ameliorated soda-solonchak is 46%.The water-stable aggregates (>0.25 mm) are distributed with the same tendency of the microaggregates(>0.05 mm) in the soils.2.Under microscope,the degree of aggregation and the size of soil microaggregates,as well as soil porosity can be observed precisely.Black soils have a spongy fabric.Soil particles are cemented by gel-like substances to form porous soil structure.Planosols show a loose bound agglomeratic fabric with lower porosity.Unimproved sodasolonchaks belong to a porphyropeptic fabric in which almost no aggregates can be found.The ameliorated soda-solonchaks have a pluctoamictic fabric in which microaggregates are formed by the gel-like subatances and mineral grains.3.The variation of the organo-anineral complexes in soils is also observed by scanning electron microscope.In fertile black soils the organo-mineral complexes are agglutinated by the gel-like substances to fbrm a loose and soft soil structure.In unimproved soda-solonchaks and planosols the particles are merely accumulated together without any evidence of eementation.While in ameliorated soda-solonchaks some gel-like substances appear on the particle surface,which means organo-mineral complexes are formed.

Abstract:用透射电子显微镜对膨润土形貌的观察,并用它来鉴别膨润土类型的方法早已被人们采用^[1,2,5]。一般认为钙膨润土的蒙脱石颗粒不易分散成薄片,而且聚集成大小不同,厚度不等的团块或花絮状集团,轮廓清楚,边缘常呈突刺状或涡旋状,而钠膨润土的蒙脱石薄片极薄,横向延续极大,边界勉强可辨^[2]。近年来,随着扫描电子显微镜在各个领域的广泛应用,也有人开始用它来观察膨润土的形貌¹⁾,研究膨润土对型砂的粘结机理同,但是还没有人用它对膨润土类型做过详细的形貌鉴别。从1978年开始,我们陆续对国内外几十种不同类型的膨润土做了扫描电镜观察。本文从膨润土类型与扫描电镜形貌关系方面作一简单介绍。