Abstract:The horizontal two-dimensional flow and vertical two-dimensional flow were tested in the laboratory and their mathematical models were developed respectively. The recults obtained from numerical calculation F with the finite difference method well agreed with those obtained from experiment. This shows that the mathematical models are applibable.The two-dimensional unsaturated flow in the soil under subsurface irrigation was simulated with the model under different conditions such as various initial water content in soil, varipus kinds of soil, different com.paction and water supply pipes with difterent diameters. On the basis of the data from calculation, the influences of various factors on two-dimensional unsaturated flow of the soil under subsurface irrigation are analyzed and some views about reasonable management of subsurface irrigation are recommended.

Abstract:The properties of fertilizer appeared under the interaction behaviors between nitrogen fertilizer applied in soil and components of soil such as adsorption by soil,leaching and volatilization from soil as well as nitrification and denitrification of nifertilizer are regarded as its agrochemical properties.Although ammonium bicarbonate is easy to decompose and volatilize and inconvenient to store, transport and apply, laboratory simulating experiments have showed that ammonium bicarbonate is more easily adsorbed by soil, less leached from soil, as compared with ammonium sulphate and urea;and its volatilization sharply decreases after incorporating with soil;only the rate of nitrification is similar to that of ammonium sulphate and urea. There fore, if the method of deep application is adopted, its effect on crops in fields can also be similar to that of ammonium sulphate or urea.The volatilization process of ammonium bicarbonate, ammonium sulphate and urea can be simulated by power regression equation Y=Ax^b, and the correlation between the initial volatilization amount (mgN/h) and regression constant A is significant. Their nitrification process on different Boils can be simulated by exponential equation Y=Ae^bx their initial nitrification rate(%) and regression constants A and B are approximate on the same soil but very different on different soils, which indicates that nitrification rate of nitrogen fertilizer after it being applied in soil depends mainly on the soil properties.

Abstract:This paper is to study a theoretical equation used to calculate field moisture capscity instead of complicated measurement in situ. It is considered that this moisture coostant includes two parts, i.e. that held by the attractive force of soil particles and that held by water surface energy. The farmer is calculated by 1.5 times of maximum hygroecopicity(Wm),i.e.% of Fnoisture at wilting point (KWm);the latter is obtained by a simplified spoil model in ideal arrangement of ball particles. It is assumed that the number of soil pores is equal to the number of soil particles.

Abstract:Simulated study in green horse on the effect of applied rates and methods of organic materials on soil structure was conducted for 4 years. The organic materials used in eaperiment were dry rice straw+dry milk vetch, rice straw, milk vetch and waterlogged compost of rice straw. Same physical conditions during the period of incubation were controlled. Results showed that the soil structure and porosity were markedly improved and the rupture modulus of soil core were decreased by application of organic materials in clayey soil. The stability of soil aggregates was positively correlated with the content of organic matter, heavy fractional organic matter, amorphous iron oxide and activity of iron oxides (Fe_n/Fe_t),while the rupture modulus of soil core were negatively correlated with the parameters mentioned above. It sees that the amorphous iron oxide may be used as an indirect index for the evaluation of high yield paddy soils with good structure. The macropore apace of the soils applying organic materials was increased significantly during the dehydration of soil, which is beneficial for the growth of upland crops on clayey paddy soils after harvest of rice. The effect of direct application of rice straw on the improvement of soil structure was much better than that of application of waterlogged compost of rice straw or mixed application of rice straw and milk vetch. Therefore, it is necessary to apply a certain quantity of rice straw for the improvement of soil structure, while sowing area of green manure crops are reduced recently.

Abstract:The purplish soils with the different properties and fertility had obvious influence on nodulation and nitrogen fixation of the alder. More nodule numbers and higher N₂-fixing capacity occurred on two Shaqimiao purplish soils and Penlaizhing calcium light loam, but less nodule numbers and lower Ns-fixing capacity was found on the heavy loam with high calcium content. and the strongly acid soils. The soil temperature in the range From 20°-32℃ was more suitable to N₂-fixing activity. It was obvious that the activity declined gradually with decreasing of temperature below 20℃. Deficiency or excess of water in the soil could cause the tremendous decline of the nitrogenase activity. Planting the alder on various purplish soils may increase soil nitrogen and be beneficial to soil amelioration.

Abstract:With reference to the recent data on neoteetonic movement in Sony-Liao Plain, the author suggests that the genetic differences between the cultivated black soil and the light chernozem are mainly determined by their parent. materials and age of soil formation. The former is derived from the sediments of middle Pleistocene on the undulating or rolling terraces and characterized by abundant humus and non-calcareous reaction;and the latter is developed on alluviumof late Pleistocene or recent alluvial deposits in the central flat part of the plain and characterized by less organic matter and strongly calcareous reactioa. The latter is much more infant than the former, and it has been formed along a sequance of swamp-meadow soil-meadew light ehernozem-light chernozem.Under the present climatic conditions, the genetic direction of the meadow soil types is constrained by their vegetative cover. Once their vegetative covers are destroyed by either natural or artifical causes, with the evaporation being intensified the soda solonchak or solonetz will be formed even under the condition of slightly mineralized ground-water. From the viewpoint of soil formation, the principle of rational use of alkaline grassland and reclamation of soda solonchak should be the protection and restoration of vegetative covers of the soils.

Abstract:The purpose of this paper is to answer the question how to transform the computer-classified maps into corresponding soil maps.The first step, i.e. the key step, is to establish the exact relationship between the machine-divided categories and the real soil categoreies. The tables for expressing their relationship were listed on the basis of the internal sequence, cluster denddrogram and the band-radiation curves of the machine-divided spectral categories and the geographical control system (cf. the author's article in ACTA PEDOLOGICA SINICA, Vol.21, No. 2).Then, on the computer printouts, the geographical control lines are drawn on basis of the geographical control system and according tv the boundaries of some spectral categorles in their internal sequence. Among the control lines, the most important are the boundaries of the various geographical control regions. The third step is to delineate the soil boundaries according to the geographical controt lines and the tabular relationship between spectral and soil categories. The final step is to adjust the crosswise and lengthwise scales of the delineated computer printouts and to transfer them to the formal soil maps with Zoom Transfer Scope. It is found that the soil map of unsupervised classification is quite consistent with that of supervised classification, and the latter is better, A comparison has been made between two computer venerated soil maps and the conventional soil map. It is shown that they are very similar, and the machine-made maps are more detailed and accurate.

Abstract:The statistical values of various properties of the soils developed on pluvial-alluvial and alluvial plains in South Xinjiang were obtained by analytical method of synthetic value (AMSV) on the basis of large amounts of data of soil properties, which is helpful for comprehension of the characteristics of the soils in the region. Simultanously, the principal composition equation, scattered point graph a.nd indexes of interclass delimitation of soils in the region were obtained, which provides the possibility for correction of the existing soil classification system of the region. Results from 32 profiles showed that the results obtained from this approach could be used as the reference for the classification of the soils in the region.This classification has also been proved advantageous not only to discriminate the soils from the data of field survey or remote sensing, but also to determine the poAssibility of soil improvement. It was showed from the results obtxined that all residual saline soil was not suitable for reclamation.In addition, the indexes of interclass delimitation for saline and salinized soils in the region are discussed. Five factors including salts in whole profile (0-100 cm),Na⁺, salts in surface soil (0-30 em),Cl^- and salts in subsoil (31-100 cm)were used as the indexes in which salts in whole profile, Na⁺ and salts in surface soil are oonsidered as the more important indexes.

Abstract:A modification is proposed for Montgomery's procedure of the colorimetric deterurination of organic acids in the soil extraets. According to the equilibrium relationship in the chemical reactions, the soil extracts are dried on a boiling water bath before the esterification proceeded. As the extract is concentrated, the determination is free from the influence of aliquot volume and the organic acid concentration of the extracts. The factors including temperature, time and pH which affect the reactions in the procedars were tested. The recovery rate of acetic acid and butyric acid were 99% and 102% respectively. Acetic acid of several organic manure incubated under waterlogged condition for 10 days determined by the gas chromatography was 86% of that determined by the procedure suggested by the authors. This indicates that the results obtained by the modified method can better reflect the actual organic acid content in soil.

Abstract:为了阐明植物养分的实际有效性,研究土/根界面的化学性质的微域差异是十分重要的^[1,3]。我们以前的工作已经证明^[2],用钾离子选择电极原位测定水稻根际微区中钾离子的分布,与用Nye的数学模型预期者基本相吻合,说明可以用离子选择电极技术研究土/根界面的离子状况。本工作继续用钙离子选择电极与Nye的模型对水稻根际钙离子状况进行研究。

Abstract:土壤水早被人类所利用。由于它具有本身的特征,对它的研究无论从理论上还是测试技术方面,都还远远落后于其他水体资源,如地表水以及地下水等开发利用的研究。自从五十年代核反应堆能提供中子源以来,中子测水方法得到了应用,并获得迅速发展。在今天,中子水分仪测量土壤水分已被认为是最好的测试方法,它具有简便、快速、准确等诸优点。随着研究的深入,势必更加完善。