Abstract:The Huang-Huai-Hai plain is one of the largest alluvial plains and it is also an important agricultural region in China.It is mainly Formed by the flooding and sedimentation of water system of the Huang,Huai and Hai rivers.Due to the flat relief and poor drainage,there is a large area of saline soil of which the groundwater is salty in the central and eastern portion of the plain.This area belongs to the semihumid and semi-arid climatic zone.Owing to the influence of Pacific monsoon,it is dry in spring and rainy and flooding in summer and autumn.The crop yield is quite unstable.Under the specific biogeographical condition,an unique regional ecosystem is formed in the plain;and the alternation of drought,flooding,salinization and alkalination induce the extreme complication and unstability of the ecosystem in this region which seriously influences the development of agricultural production and national economy.

Abstract:Guizhou is a mountainous plateau situated in subtropical region.Desilicification and allitic processes are both occurred in soil forming process of the regional soils such as yellowbrown earth,yellow earth,red earth and latosol.The effect of parent material on the soil depends on the types and property of different parent rocks.For regional soils,parent material is the criterion for the classification of soil family level.The formation and property of regosols are affected more greatly by the parent material,while the influence of regionality is only reflected in the classification of suborder level.The influence of vegetation and cultivative activity on the soil genetic property is reflected markedly in fertility of soil and the most remarkable influence of human activity is on the paddy soil.Guizhou is a mountainous plateau situated in subtropical region.Desilicification and allitic processes are both occurred in soil forming process of the regional soils such as yellowbrown earth,yellow earth,red earth and latosol.The effect of parent material on the soil depends on the types and property of different parent rocks.For regional soils,parent material is the criterion for the classification of soil family level.The formation and property of regosols are affected more greatly by the parent material,while the influence of regionality is only reflected in the classification of suborder level.The influence of vegetation and cultivative activity on the soil genetic property is reflected markedly in fertility of soil and the most remarkable influence of human activity is on the paddy soil.

Abstract:The experiment of evaporation and movement of soil water were carried out in the tpolyniethylmethacrylate cylinders of 5 em in diameter and 120 cm high.The soil used in the experiment was a heavy loam;and CaCl₃,was used as the tracer.Four treatments were laid out on the basis different soil moisture contents,they were (a) the maximum hygroscopicity,(b) wilting percentage,(c) the moisture content of the capillary bond disruption,and (d) the minimum water-holding capacity.The experimental data showed that,under evaporation condition,the lower limit of water in the liquid form in soil is near the wilting percentage.When soil moisture content is lower than the wilting percentage,the movement of the soil water in liquid form is usually extremely weak.

Abstract:The soil-forming factors on Xizang Plateau,such as climate,vegetation,topography and hydrographical conditions have changed greatly since the end of Pliocene as the result of uplifting of the Plateau.It exerted deep influence on soil genesis and evolution in this regicn.The field investigation showed that soils bearing composite profile with paleosol layer are widely spreaded.The morphological characteristics of these composite soil profiles may indicate,to a great extent,the polygenetic processes of soils on the Plateau.To give evidence,micromorphological study of soils bearing paleosol layers has been carried out.Thin section observation indicates that the polygenetic characteristics of soils are closely related to the historical natural evolution of Xizang Plateau.

Abstract:The present paper deals with the relationship between the soil nitrogen supply and the rice yield.The pot experiment of late rice on four representative paddy suits in Zhejiang province,namely,the Bluish gray clayey soil (a stagnogley paddy soil),the Red Brume soil (a percogenic paddy soil),the Rust mottled clayey soil and the Cray clay loamy soil (periodical submergic paddy soil) was carried out with the fertilizer labelled by ¹⁵N.The vreliminarv results are summarized as follows:(1) The rice plants on the more fertile soil,such as the bluish gray clayey soil,absorbed more soil nitrogen se 1.3 times than that on the gray clay loamy soil with a lower fertility.Therefore,it seems that the fertility of soil may be considered as a very important factor which would significantly affects the absorption of the soil nitrogeh by rice plant.

Abstract:Experiment has showed that the effect of CP on the inhibition of nitrification is significant.However,the effect of CP on the decrease of N loss is varied with soil properties.The beneficial role of CP for retaining nitrogn in ammonium form in acid paddy soil may not be attained in calcareous soil,since the volatilization of NH₄-H is usually enhanced in the soil.In the present experiment,the uptake of fertilizer nitrogen by rice plant through the application of CP is increased alightly,but no response is found in crop yield.Field experiments have also proved that the good effect of CP on the rice yield is found on infertile soils on which only a small quantity of nitrogen fertilizer or manures is applied,or even on calcareous soil.

Abstract:This present paper deals with the characteristics of phosphate adsorption isotherm of soils and clay minerals.The concentration of phosphate solution was divided into nine levels of which KH₄PO₄.ranged from 15.5 to 310 P per ml,the solutions were prepared and mined with various amounts of KCl solution (as supporting electrolyte) to keep the ionic strength of solution in a constant (0.01M).The ratio of sample weight to solution volume is 1:20 for soil,1:5 for montmorillonite,1:10 for kaolinite and 1:50 for anion ezchange resin.Each sample was shaken for 1 hour and then stood for 24 houre at 35℃.The amount of P adsorbed was calculated from the difference between initial and final concentration of phosphate in solution.

Abstract:The fluvo-aquic soils widely distributed in the great plain of north China are developed on the recentalluvium under the influence of seasonal fluctuation of ground-water.Owing to the variation of tezture and water regime of soil the degree of soil development is quite different,which leads the occurrence of the different patterns of land use.The present article deals with the study on the classification of basic categoriea of fluvo-aquic soils.The soil families of fluvo-aquic soils are mainly disting uished on the basis of the tezture of alluvium on which the soils are developed,and the teztural profile may reflect the characteristics of soil formation processes,the distribution and location of genetic horizons and the hydrological conditions,and these characteristics can influence the development and utilization of the soils.

Abstract:The composition of clay minerals and the contents of K-bearing minerals and slowly available Potassium of nine samples were determined by chemieal and X-ray diffraction methods The resuits showed that the clay minerals Present in the clay fraction (<2μ) of all these samples were hydromioa,ehlorite,kaolinite and montmorillonite etc.The eontent of K-bearing minerals was very high(35%) in the soil derived from the Pruplish sliale,and followed by that in the soil derived from lacustrine deposits (25%),while those in the other soils ranged only from 14-19%.

Abstract:Interference by living plant roots is usually found in decomposition studies with no labelled plant materials carried out under field conditions.It has been found that this interference can be completely eliminated by using porous carborundum tubes with mainly of 140μ×70μ,as the containers for soil and plant material being and the hydro-thermal conditions of the soil inside the tube was identical with or approximate to that outside the tube under submerged and upland conditions respectively.