Abstract:This paper deals mainly with the soil forming process and genetic properties of the allitic soils in China.(1)Investigation has shown that the genesis of the allitic soils in China is closely related with the environmental factors in tropical and subtropical regions.Allitic soils in China are developed under the interaction of the allitic and biological processes.The former is the main process of soil formation,while the latter is the premise for development of soil fertility.In addition to the geological factors,the current biological conditions,i.e.contemporary soil forming process also plays important roles on the development of the allitic soils.

Abstract:Water regime in paddy soil is one of the main factors which dominate the eluviation and muviation of mineral elements and affect the yield of rice and wheat.A preliminary study was made by modelling soil column experiment for the influence of soil water regime on the eluviation and illuviation of mineral elements in soil and their differentiation in soil profile,as well as its relation to the growth of rice and wheat.Experiment showed that the content of dissolved oxygen in soil column was restricted by the soil water condition;the more the amount of percolating water,the more the dissolved of water oxygen in soil;and the average value of Eh in soil was lowered with the decrease of percolation.

Abstract:1.In loess region,the average content of total Zn in soil is close to that of loessal parent material,but lower than that of the country and higher than that of the world.2.The relationship between the soil texture and Zn content is quite clear,the coarser the soil texture,the lower the content of Zn in soil.The content of available Zn in soil is positively correlated with the content of organic matter and negatively correlated with the content of CaCO₃ in soil.In this region,the content of organic matter is lower and the content of CaCO₃ is higher.Consequently,the soil deficient in Zn is widely distributed.and it is about more than 50% of area of this region.In addition to application of Zn fer tilizer,such measures as application of organic fertilizer,green manure,afforestation and sowing grass,sewerage irrigation,application of a great quantity of Mn fetilizer,etc.may increase the content of soil available Zn.

Abstract:Suzhou district is one of the highly productive agricultural regions of intensive farming and high fertilizer imput.In the recent years,the rate of application of nitrogen fertilizets for each rice crop season in this region has attained an average above 150 kg.of N pet hectare which is believed to be the amount required by rice plants in order to get 7500 kg.of grain per hectare.It was showed by ¹⁵N-tracing experiments with the similar fertilizer application rates that the loss of fertilizer-N during tie growing season accounted for 30% to 70% of the fertilizer-N applied in this region,and some studies revealed that deep-dresing,granulation and appropriate timing of the application for nitrogen fertilizers seemed to be effective for increasing the efficiency of fertilizer-N in the rice field.

Abstract:The present paper deals firstly with the indexes of activation of iron oxides in soil on the basis of the data from previous paper and reference literatures.It is considered that the change of activity of iron oxides in soil.may be summarized as activation and aging.Though the change is not a reversible reaction,the aged iron oxides can be activated by the ac lion of organic matter and atmospheric factor.It is also o}nsidered that mineralogical patterns can not reflect quantitatively the change of activity of iron oxides;however,it can be estimated quantitatively to a certain degree by the content of amorphous iron oxides.

Abstract:The present paper deals with a comparison of regression equations for describing arsenate adsorption by soils.Five soils including manured loessial soil,loessial soil and yellow brown earth collected from Shaanxi Province were used in experiment.The results obtatined has shown that Freundliche equation fits better for the experimental data than those and the revised ones of Temkin and Langmuir.The As adsorption curve derived from Freundliche equation is identical with the trend of variation of As adsorption measured directly,its standard deviation (S) is minimum(4.3-39.4),and the correlation coefficient (R²)is maximum(0.91-0.99).The curves derived from other equations differ greatly from their respective values measured directly.

Abstract:The present paper deals with preliminary study on the influence of hydrolyzed polyacrylonitrile on phosphate and nitrogen in loessal soils,the results obtained are summarized as follows:1.The phosphorus fixation in soil is decreased and the available phosphorus is increased with the increase of the concentration of hydrolyzed polyacrylonitrile applied phosphate.2.The ammoniacal nitrogen content and the ammoniacal nitrogen released from soil are increased with the increase of the.concentration of hydrolyzed polyacrylonitrile applied.

Abstract:With the cluster analysis method,the role of the totality of soil enzyme activities in the evaluation of the level of soil fertility is discussed.Studies on black soil,meadow black soil and brown earth show that it is rather possible and feasible to evaluate the level of soil fertility with the totality of soil enzyme activities.

Abstract:Kriging is a method of estimating values of properties at places without bias and with minimum error from observed values in the neighbourhood.The method was applied to measurements of total nitrogen in the top layers of the soils in Zhangwu County in China.After transforming the measurements to logarithms to stabilize their variances,the semi-variogram was computed from them.The semi-variogram showed spatial dependence extending to 50 bm,although it had a large non-spatial,or "nugget" component.Mathematical models were fitted,and the one giving the best fit in a least square sense was used to estimate values and their estimation variances on a fine grid(1.25km) from which isorithmic maps of the county were drawn.

Abstract:The geochemical behaviour of elements in soils is closely related to their properties and soil development,as well as the bioclimatic condetion.And the contents of the elements in soil ate also related each othw.Ten major elements in soils were used for the principal component analysis in order to group the soils geochemically.On the basis of the principal component analysis,the soils of the tropical and subtropical China were distinguished in seven.types:the ferric.alditic,siferric,siallitic,quartzose-silicic,kamagnesian and the carbonated.The equation of principal component analysis was established for distinguishing soil E;eochemical type of a unknown soil.

Abstract:The contents of Cd,Hg,As,Cu,Zn,Pb,Co,Mn,Ni,Cr,Li,Fe,Ti,Ca,Sr and Zr in 91 samples of soils developed on alluvial deposits in Tianjin region were determined by Xray fluorescence and colorimetry and their mechanical compositions were determined by gravimetry.The correlation between the rnntents of those elements and machanical compositions of the soils were studied,and the data obtained indicate that the soil particles with 0.01 mm diameter is a obvious critical limit.

Abstract:It is well-known that the charged soil clay induces a liquid-junction(diffusion) potential at the interface salt bridge-clay sediment.However,careful observations revealed that it was not necessary for the soil to directly contact the salt bridge to create such an effect.Soil mass could cause a liquid-junction potential with a thickness of several millimeters from the surface outwards,and the sign and the magnitude of the potential were closely related to.the charge of the soil.The yellow brown soil carrying a net negative charge caused a negative potential,while the potential caused by latosol carrying net positive charge wa,positive in sign.When the soil clay was mixed with silica powder to decrease the volume charge density of the soil mass,the potential decreased.This long-range effect on the liquid-junetion potential is directly in conflict with the commonly accepted concept about the electrical double layer,in which the effective thickness of the layer is visualized to be only several thousand Angstrom units.

Abstract:The organic matter content and decomposition rate of peat are two important properties in relation to the utilization of peat in production.According to organic matter content and decomposition rate,the peat of China is divided into three groups and nine types.The classification system of peat is listed in table 2.