Abstract:A critical review of the historical development of soil physical chenustry in China is made. The main points are summarized as follows: 1. Chemical studies of soils: Chemical studies of soil, which is considered as the initial stage of the developwent of soil physical chemistry in China, started in the early tlyirties of this century. They mainly dealt with the chemical composition and exchangeable cations in relation to the genesis and classification of soils. Some works on quick test have also been made. Only very limited number of workers have devoted to some physico-chemical properties of soils such as amphbteric behavior, phosphate fixation and effect of pH on the color of humus. It was on this weak foundation that soil physical chemistry has been developing since the establishment of the People's Republic. 2. Studies on soil colloid: In a series of papers by Dr. Hseung Yi and his coworkers, the mineralogibal composition of the colloidal fraction of a variety of soil types was studied by means of chemical analysis, X-ray diffraction and differential thermal analysis. Some works on swelling and shrinkage, potentiometric titration curve, electrophoresis, and dispersion and flocculation of soil colloid have also been carried out.

Abstract:This article deals with the favorable influence of earthworm on soil structure formation. Investigation revealed that most of the smoothly egg-shaped, elliptic or round aggregates in sail were the products of the life activities of earthworm. Electron microscopic study showed that earthworm played an important part in the formation of organo-mineral complez in soil. Therefore, the aggregates formed by earthworms possessed a higher water-stability and the ability of nutrient supply and retentibn. It is assumed that there is possibility of using the earthworm activity as a means for the improvement of soil fertility.

Abstract:The present article deals with the patterns of soil N the uptake of soil and fertilizer N by rice plant and the fate of fertilizer N in relation to the forms and methods of placement of N fertilizer in the paddy soils of Suchow District, Jiangsu Province. Field experiment was carried out with ¹⁵N-tracer technique. The soils used for the experiment are developed from the alluvial-lacustrine deposits with a feature of clay loam.

Abstract:This paper deals with the study by plot experiments, on the relationship between soil conditions of different cut-over areas and reforestation. The results showed that the hydrothermal regime of the cut-over area where trees were removed sia years ago could possibly meet the needs of growth of regenerated seedlings. Owing to the significant variation of the hydrothermal regime of the surfac soil (0-20 cm) of cut over area nn the sunny slope at high altitude, it was necessary bo take proper sheding measures for the favorable growth of seedlings. The larger amount of carbon dioxide that was evolved from the soil surface and contained in the soil of the cut-over area as compared with that of the forest land showed that the biological activities were intensified, the decomposition of organic matter was accelerated and the contents of nitrogenous nutrients were increased. All these were conducive to the improvement of soil fertility and thereby benefical to the growth of young trees and reforestation of the cut-over area.

Abstract:During past years the status of the trace elements in soils of guzhou and Huaiyin districts of Jiangsu province were studied. The main soil type in these districts is yellow fluviogenic soil derived from the alluvium of the yellow river. Analytical results revealed that the soils of these districts are very poor in manganese, molybdenum and zinc, but rich in available boron and copper. The total content of manganese in soils of these districts varies from 262-662 ppm with an average content of 425 ppm. The exchangeable manganese can not be detected in the surface soil of forty-three percent of the analyzed samples. Forty-nine percent of the easily reducible manganese is lower than the critical value 100 ppm. The molybdenum content ranges from 0.4 to 2.6 ppm with an average of 0.8 ppm. The available molybdenum content is very low and that in the surface soil of ninety percent of the samples is below the critical value (0.15 ppm, extracted by the Grigg's solutibn). The content of boron varies from 15-72 ppm with an average of 47 ppm. The water soluble boron is very high due to the salinization. The available zinc extracted by DTPA solution is also very low. Ita content of eighty-eight percent of the analyzed samples ig lower than the critical value (0.5 ppm). The available copper extracted by DTPA solution is higher than the critical value. Field experiments were carried out in sixteen counties in coorperatibn with local agricultural institutions and people's commons. Fertilization with manganese brings about the increase im yields of wheat, cotton, sugar beet, maize, winter rape, sweet potato, soybean, pea, peanut and several leguminous green manure crops. Mo-fertilization leads to an increase in yield of leewminous crops and Zn-fertilization leads to the increase in yields of paddy and maize. Response of sugar beet and peanut to boron fertilizer is confirmed also.

Abstract:In the process of soil water movement, the soil water content in the surface layer of a sandy Boil changed firstly in the initial stage. In the duration of time, the layer in which the soil water content began to change gradually moved downward in the soil profile. After a certain time, about 12 minutes, such variation occured mainly in the middle part of the soil profile and changes either in the surface layer or in the bottom Payer of the soil profile were insignificant.The quantity and the rate of soil water movement were increased with the increase of difference in hydraulic potential. Owing to the different location of the slow permeable stratum in the soil profile, the rate of soil water movement varied significantly. The more shallow the slow permeable stratum was located in the soil profile, the less the quantity and the rate of soil water movement occured. The result of the experiment has shown that the use of radioactive isotope ¹³¹I for the study of soil water movement is a more convenient method with higher sensitivity, and its use also provides a possibility to observe the process of soil water movement continuously.

Abstract:The effect of soil compaction and clod distribution of two clayey soils on the growth of rice in southern Jiangsu province was studied. The distribution of soil clods in the plough layer under different ploughing methods was also investigated. The results obtained denoted that the compaction and the proportion of soil clod and fine soil particles influenced the growth of rice markedly. The effect of soil compaction on the growth of rice was produced by the mechanical resistance of soil to the penetration of roots, the inhibition of nutrient transformation and the unfavorable physical properties of soil moisture. The mineralization of soil nutrients might be mainly affected by soil clodding. Grinding the soil in water might promote the release of NH₄-N. The release of NH₄-N was obviously less in clod >1 cm in diameter. Therefore, it is suggested that the quantity of soil clod <1 cm in diameter in the plough layer may be taken as an important index for the evaluation of spring ploughing.

Abstract:The moisture retention of several important soils in China have been measured with the pressure membrane apparatus. These soils are the laterite, the red soil (parent material), the loess, the purple soil and the light meadow soil of different textures, namely sandy loam, light loam and medium loam. The results obtained showed that the finer the soil texture, the higher the soil moisture capacity is in a higher soil suction range;whereas in the lower soil suction range, the moisture capacity might not be related to soil texture. The field capacity and wilting percentage of the light meadow soils with the three textures mentioned above in North China Plain were compared with those of the same soils under the soil suction of 0.1-0.3 and 15 bars respectively. Results showed that the wilting percentage of all these soils of the three textures approximated to that under the soil suction of 15 bars. The soil moisture retention and the availability of soil moisture under different soil suction are discussed with the concept of specific water capacity. It is indicated that specific water capacity was decreased rapidly with the increase of soil suction, i.e., the water released from soil to the plant would rapidly decrease. Thus, the availability of soil moisture would decrease too. The calculated results showed that the specific tvater capacity of moit under soil suction of 10-15 bars was about 100 times less than that under soil suction of 0.1-0.3 bars.

Abstract:Highly weathered coal debris and peats were pulverized into fine powders. They contain humic acid ranging from 30-50%. Effects of the rate of mobilizing phosphorus from rock phosphate powders by these humified materials were studied in incubated culture, pot experiments and field experiments. Results obtained are summarized as follows. 1. The acidity of pure humic acid was adjusted to pH 4.2-7.1. The humic acid solutions were mixed with powdered rock phosphate in culture dishes and incubated at 29±1℃ for two weeks. Rate of liberation of phosphorus from Kai-yang rock phosphate, a fluor-apatite containing 35% P₂O₅, was about 6-17% of the theoretical value of the hydroxyl group of humic acids. It increased with the increase of acidity of the humic acids. Powdered rock phosphates were also cultured with coal powders. In this regard, the rate of liberation of phosphorus from the rock depends upon the content of humia acid in the weathered coals.

Abstract:Investigation and field experiment on the water and salt regime of paddy soils were carried out in the depression area along the Yellow River in Fengqiu county, Honan Province. The results obtained are as follows: 1. Because of the light texture of the soils from sandy loam to loam, salt injury was resulted from the high capillary conductivity of soil water and the readily accumulation of salts in the surface soil, even under the condition of low concentration of ground water. The submerged water in rice field could wash the salt downward, and was also conducive to the desalination of the ground water.2. Secondary salinati}on of the soils around the rice field was caused mainly by the rise of ground-water level due to the irrigation of the rice field. The outward spreading of secondary salivation of soils was induced by the high ground-water level of this adjacent area as compared with that of outer area, i.e., by the occurrence of a hydraulic potential gradient in the surrounding soils of rice field. The water and salts in soil moved from the place adjacent to the rice field with higher hydraulic potential to places far from the rice field with lower hydraulic potential, and were accumulated there.

Abstract:This paper deals with the regularity of annual change of soil moisture in the plain of the Songhua River and the Nen River. The conclusions are as follows: 1. The characteristics of the soil moisture change in the seasonal frozen region are:In the winter, in the area of high ground water table, large quantity of water is transported from the ground water to the frozen layer. In the spring, following the thawing of frozen layer, a water layer lying over the frozen layer is formed and becomes main source of the soil moisture. This process, therefore, deeply influences pedogenesis. 2. The soil water lying over the seasonal frozen layer is, in fact, ground water in the surface soil. The underlying frozen layer is impermeable. The soil water is supplied continously by melting snow, rainfall, irrigation water and water from the thawing frozen layer;it is lost through horizontal run off and evapotranspiration. 3. In the rainy spring; the presence of the seasonal frozen layer is one of the main factor of waterlogging. The salt accumulation in soil is related with the high concentration of salts in the soil water lying over the frozen layer which is near the ground surface. It has no concern with the ground water.

Abstract:The physico-chemical properties of four samples of bentonite collected from Jiutai in Jilin Province, Changwei in Shandong Province and Nanjing in Jiangsu Province were studied. X-ray diffraction and chemical analysis of these samples were made and their particle size distribution, viscosity and cation exchange capacity were determined. Results obtained showed that all these bentonitea were Ca-Mg clays. The sample eollteted from Nanjing had a higher exchange capacity and that from Jiutai contained more exchangeable sodium.

Abstract:The determination of total fluorine in lacustrine sediments using a fluorine ion-selective electrode was studied. The sample was brought into solution by fusion with sodium hydroxide or sodium peroxide and sodium carbonate. It is found that same results were obtained with the two fluxes, but sodium hydroxide was preferable,owing to its ready removal from crucible. The interference of Al, Fe and other metal ions might be eliminated by the addition of mixed solution of complexing agents—CDTA(0.05M),sodium citrate (1 M) and sodium chloride (1 M).The proportion of the mixed solution to the test solution used in this methed was 4:6. It hex been shown that Gran's graphucal method is simpler and more accurate than other methods for the calculation of the fluorine content determinated by the ion selective electrode.