Abstract:Authors systematically collected 147 samples(at last constituting 100 samples for analysis) of Malan Loess in Loess Plateau and 54 elements were analysed for each sample.Abundance of each element was calculated by means of weighted average method.The results showed that chemical compositions of loess were very similar to each other in all parts of Loess Plateau with a good characteristic of homogenity.Moreover,the average chemical compositions of loess were very close to Clark values of crust,which are used at present.Therefore,the average chemical compositions of loess may be used to represent average chemical constituents of comtinetal upper crust.From theoritical point of view,typical eolian loess has a very large area of material sources and was also mixed homogeneously.Consequently,using it to calculate Clark values of upper cmst should be more reasonable,more representative and more substantial than previous methods.it could be a new way for investigation of Clark values of crust and a new field of loess geochemistry study in future.

Abstract:The study was carried out on the basis of a detailed scale in a 30 km² test aera by using all available site and layer data of main and mini pits with the grids of 30m by 30m or 50m by 50m.This paper describes the punctual and areal variability of the soils in the main test area by the result from;——Frequency distribution of attribute values from all the observations;——Variogram analyses of layer depth,colour,pH,available P,and K of all the topsoil samples from three subareas(Y.D.F);——Kriging iraterpolation and construction of isoline maps for the attributes of subarea Y.All the studywork was performed on a GIS system supported by a microcomputer and the softwares ARC/INFO,IDRISI,dBASE and GEOEAS.

Abstract:The research results showed that in the desertification process of the soils,silt content,organic matter,available nutrients and water-holding capacity were gradually reduced but soil temperature ane pH rose;Worsening of the soil properties resulted from decreasing of silt and clay particles and organic matter caused the coarsing of soil particles,the lowering of water-holding capacity and the loss of nutrients in the process,the danger by wind erosion of soil was more serious than that by wind deposition;and in the desertification process of farmland soils,worsening of soil physical and chemical properties had both continuity and discontinuity.

Abstract:The dynamic changes of water regime in sloping uncultivated red soil derived from Quaternary red clay distributed in Jiangxi Province were investigated during 1990-1993.Resuits show that the water regime in sloping red soil changed apparently not only in a year but also between years.The water content of red soil under high water potential is higher.However,in connection with the specific structural characteristic,the available water content in red soil is lower,which becomes an inner important factor leading crops to subject draught hazard in Summer and Autumn.The water storage in sloping red soil is richer in the first half of a year,then decreased from the beginning of July in the second half of the year.In later time a negative value of available water content appeared at soil depth of 0-50 cm.Results also shows that according to the ratio of the measured water storage of soil to the calculated rhaximum storing water capacity a certain amount of empty water storing capacity at soil depth of 0-100 cm where can accept the rainfall could be found even though in first half of a year with richer rainfall.Moreover,a richer water storage at soil depths of 100-200 cm and 200-300 cm is presented in the second half of a year with severe shortage of rainfall.Consequently,to increase the acceptance of rainfall in first half of a year and to use the richer water storage in deeper soil layers in the second half of a year are an effective way for raising the use efficiency of water resource in red soils.

Abstract:The soil adsorption model and immobile water model were established through experiments of isotherm static adsorption and dynamic adsorption,and hydrodynamic dispersion in saturated soil respectively.The numerical model of the characteristic method combined with finite element scheme (CMFE) was proposed to solve the mathematical model of solute transfer through saturated-unsaturated soil under the influence of soil adsorption and immobile water conditions.The solute transport were simulated by the CMFE method under evaporation and infiltration experiment conditions.A comparison among the mathematical models considering the following four cases respectively:(i) neglected influence of soil adsorption and immobile water,(ii) soil adsorption only,(iii) immobile water only,and (iv) both influences of soil adsorption and immobile water was done systematically.It was shown that the influences of soil adsorption and immobile water on solute transport were very large and could not be neglected in the soil water-salt control and monitoring,in the research of salinized soil,and in the accurate and quantitative research.

Abstract:This paper discusses the reversible process of ion exchange between soil and aquatic environment.On the basis of combining material balance with local ion exchange equilibrium,a mathematical model of 1-d convection,dispersian and ion exchange reaction taking place in soil column is built.Results obtained from ion exchange experiments by the authors and reported by previous literature all verified the model.As a consequence,the temporal-spacial distribution of ions A and B in two phases has been predicted.In view of current emphasis on quantitatively predicting the pollusion of soil and groundwater,this model would be helpful in practice.

Abstract:Upon the experimental study by using methods of equilibrium vapor pressure and differential thermal analysis,the distinguishing features of adsorption and desorption isotherms of the gaseous water in soil at 20℃ and 30℃ and the characteristics of desorption heat of the adsorbed water are discussed in the present paper.The results are shown as follows:1.When the relative vapor pressure reached to 72-75%,capillary moisture condensation began to appear in the tested soil.2.Besides the clay content,specific surface area and organic matter content of soil,temperature also affected the amount of gaseous water adsorbed in soil,and the amount of residual water in samples of desorption equilibrium at 30℃ was more than that at 20℃ while the moisture content of adsorption equilibrium samples at 30℃ was less than that at 20℃ in the general range of the relative vapor pressure.3.A hysteresis effect existed between the adsorption and the desorption of soil water vapor,and its extent showed a consistent order with the clay content and specific surface area of soil.The hysteresis effect also strengthened with increasing temperature.4.The partial molar desorption heat of the adsorbed water at very low soil moisture content was far higher than that at high soil moisture,suggesting that it mainly depends on chemical adsorption for dry soil to adsorb water vapor molecules at the initial stage.

Abstract:The kinetics of axed ammonium release from plough layer of manured loessial soil (expressed as S₁₁,)and the soil where organic matter (OM.)was destroyed by oxidation (as S₁₂) in Shaanxi Province of China were investigated using aerobic incubation-intermittent leaching method.The incubation was lasted up to 20 weeks to reach the maximum NH₄⁺ release.The kinetics of fixed NH₄⁺ release were evaluated using the Elovich,parabolic diffusion law,first-order diffusion and zero-order equations.The first-order equation described the NH₄⁺-elease kinetics best as evidenced by the highest correlation coefficient (r) and the lowest valise of the standard error of the estimate (SE).The parabolic diffusion law also described the data satisfactorily,indicating that fixed NH₄⁺ release was a diffusion-controlled process.Although the Elovich equation was also suitable to fit the NH₄⁺-release,the zero-order one was not as good as above ones,as shown by higher SE values than those found with the other equations.fixed NH₄⁺-release rate coefficient (k_r) was 0.1097/week and 0.08834/week,and maximum NH₄⁺-release amount 98.42mgN/kg soil and 85.25mgN/kg soil as well as the half time values of NH₄⁺-release (t_1/2)6.32 weeks and 7.85 weeks for S₁₁ and S₁₂ respectively.Both nitrification and soil organic matter affected fixed-NH₄⁺ release.

Abstract:To elucidate the chronological characteristics of the Xuancheng profile in Anhui Province,the ESR ages of 10 samples were determined.The results indicated that the ESR age increased with the increase of stratum depth and followed the stratigraphic sequence.If taking the Brunhes-Matuyama boundary (B/M) (730ka) between early and middle Pleistocene,based on previcus researches and our ESR dating results,the gravel layer and the upper silt layer could be assigned to the later stage of early Pleistocene epoch(1000-730ka),Plinthitic red earth layers and-brown-yellow eolian sediment layers (from the 15th layer to the 6th) to the early stage of middle Pleistocene epoch (730-400ka),and the isotropic red earth (from the 5th layer to the 3rd) to the later stage of middle Pleistocene epoch (400-100ka).

Abstract:P avAllability of water-soluble phosphate fertilizer decreased with time in calcareous soil.During a short time(two months),about two thirds of fertilizer turned into inextractable phosphates with 0.5mo1/L NaHC0₃.The fractions of the phosphates were primarily Ca-P,Al-P and Fe-P.Under conditions of corn growth,22.6-27.8% of fertilizer-P was transformed into Ca₂-P,27.5-30.6% into Ca₈-P,9.1-10.0% into Al-P,10.5-15.6% into Fe-P,while 11.3-18.8% was absorbed by the corn plants.Ca₂-P,Ca₈-P,Al-P and Fe-P phosphates in calcareous soil were avAllable for corn.The DWPP (dry weight of corn plant produced by 100mg supplied phosphorus of the four phosphate-types) in a decreasing order:Ca₂-P>Al-P>Ca₈-P>Fe-P.Ca₁₀-P phosphase was unavAllable for corn.

Abstract:A field experiment was carried out to study P absorption by hybrid rice and P supply by soil as well as the effect of P on the growth and physiological effect of hybridied rice.Results showed that for hybrid rice with a high yield of more than 1000kg,the P requirement of early rice was more than that of general cultivar,while that of late hybrid rice was less than that of general cultivar.The amount of P absorbed by hybrid rice during the middle growing stage was over half of the total P absorbed during its whole growing period.However,the P supply by soil was less at the middle growing stage of rice.When rice plant suffered from phosphorus deficiency,it grew with short,small leaves and few tillers.Phosphorus fertilization could make rice grow normally,ripen early and get high yield.With the increasing of phosphorus applied the contents of Pin rice leaves and seeds as well as shoots ail increased.In the case of insufficient supply of phosphorus protein and nitrogen contents in the leaves of rice decreased.Fertilization of P enhanced the rate of photosynthesis of leaves,raised the grain yield and shortened the growth period of rice plant.It was found that the decrease of phosphorus content in leaves of rice was accompanied by an increase of starch accumulation and a decline of sucrose:Lack of phosphorus would decrease the efficiency of nitrogen and potassium applied,while phosphorus application could enhance the absorption and use of nitrogen and potassium by hybrid rice.

Abstract:绿肥牧草从改变复垦层生态环境的速度与作用看来,与其它作物相比,确实可称为土壤改良之先锋植物^[1]。七年的复垦试验表明,只要采取适当措施,绿肥牧草无论在有无覆盖的研石山风化物上均可正常生长。它对于歼石山的利用改造有着重要的作用,可改善歼石山的生态环境,产生良好的社会效益和一定的经济效益^[2]。

Abstract:长江三峡工程是当今世界上最大的水利工程,具有防洪、发电、航运等巨大的综合效益。金属材料的土壤腐蚀是该工程建设中不可忽视的一个方面。因此三峡坝区土壤对钢铁的腐蚀性的研究是一个有意义的课题。