Abstract:A model based on the physical process of water absorption by plant roots has been suggested in this paper. Data obtained from the comparison between modeling results and experimental results showed that this model is quite satisfactory for prediction of soil moisture regime. Quantitative description of water potentials in soil, plant and atmospliere. In describing the interlinked process of water transport was made in the modelling water movement process, and the characteristics for process of energy consumption and transformation in the water movement process was also investigated simultaneously. It was also showed from the results obtained that the relationship between water absorption was close related to the effective root density. Therefore, it is of most importance to promote and strengthen the development of plant roots.

Abstract:This paper presents the properties of oxide surfaces in soil colloids, including zero point of charge (ZPC), titration curves,amount of hydroxyl(OH) released, and adsorption of NH₄⁺ and Cl^- under various pH.The results showed that as compared with the properties of siloxane surface in montmo-rillonite, the oxide surfaces supplid larger amount of variable charge, the sesquioxide in soils increased the ZPC, but the permanent negative charge and organic matter decreased the ZPC of sons. As clay acids, the proton on oxide surfaces dissociated gradually, so the titration curues showed no inflexions. The density of hydroxy and hydrous group on oxide surfaces which responded to specific adsorption of ion were higher.So far as the chemical formula is concerned, the oxide surfaces in soils are commonly Si-OH, Al-OH and Fe-OH. They can coexist to one kind of soil. The Si-OH suh-surfaces of oxide with low ZPC usually supply negative variable charge, the Al-OH and Fe-OH sub-surfaces with high ZPC supply positive variable charge.

Abstract:The water-soluble decomposition products of different plant materials and soils were separated into three fractions according to their molecular weight, namely smaller than 500,500-1000 and larger than 1000, and the concentration of complexing agents and the stability constants with Fe²⁺ or Mn²⁺ ions were determined. The three fractions accounted for 31%,36% and 33% on average of the total cotnplexing agents respectively, the fraction of a larger molecular weight was higher in proportion in the decomposed materials of plants having more stems. The stability constants of Fe(Ⅱ)-and Mn(Ⅱ)-complexes for the larger molecular weight fraction were comparatively larger by an order of magnitude of 1-2. The logk values for Fe(Ⅱ)-complexes were larger than the corresponding Mn(Ⅱ)-ones.The complexing agents in the decomposition products of plant matericals carried both negatives charges and positive charges. Fe(Ⅱ)-complexes showed a high stability against air-oxidation.

Abstract:The effects of Cd, As and Pb added to paddy soil on microbes in soils were assayed in pot experiment. Values of ED₃₀ fungi, actinomycetes, bacteria and nitrifiers were estimated. The texicity of the three elements on microorganisms in soils tested is in the order of As>Cd>Pb.In pot experiment, the luminescence of Plzotoziacterium phosphoreum spp. T₃ showed strongly negative relation to the concentration of the three elements. In field investigation, it is also strongly negatively related to the concexttration of Cd, but moderately related to that of As and Pb.It was defined by pot experiment that luminescence "100%" and "80%" of the strain T₃ could be regarded as critical luminescence of two grades, and so the critical concentrations of metals added to the potted paddy soil corresponded with it was estimated.

Abstract:The results of two years field experiments with corn on cultiveted upland red earths in Zhejiang had showed that the extraction of available P with acidic extractants was better than that with alkaline extractants. In oder to farther prove this conclusion, four different experiments were conducted: (1) fractionation of soil P associated with statistical calculation, (2) determination of correlation coefficients between different forms of P and the results of different extraction methods, (3) calculation of the difference of Al-P, Fe-P and Ca-P of three soils before and after glowing a season of wheat, (4) isotopic dilution method of Dumbar and Baker. Results of the experiments showed that the principal form of available P in cultivated upland red earths is Al-P. Due to the acid soluble property of active solid Al-P, acid extractants are more satisfactory and reasonable. In this paper, the authors recommend Bray I and Mehlich Ⅲ as the most, convineant extractants for available P in cultivated upLlnd red earths in Zhejiang. Calibration scale of these two methods and critical values of P in soil for corn by five method are given in this paper.

Abstract:The Tianshan Mts. lie across Junggar and Tarim basins, spanning 1700 km from the west to the east. The main soils on the iaountain lands include mountain chernozem(1100-1700 m), mountain gray cinnamon forest soil(1700-2800 m), subalpine meadow soil(2800-3000 m) and alpine meadow soil(3000-3500 m). The contents of total and available Mn, Zn, Cr, Ni, Co, Cu and Sr in the soils were deterrnined.The results showed that the total contents of all the trace elements determined were more than the mean values of soils in China and of the world. The available contents were mostly more than the critical values.The contents of total trace elements except Sr tended increased with the increase of elevation on which the soil was located, but no horizontal variation was found. Sr content in soil and plant was higher. The distribution of the crate element was mainly related with parent matcrials and organic matter content of the soils.

Abstract:The data obtained from the crperiment of continuous liming for three years under triple cropping system of rice-rice-barley on the paddy soil derived from Quaternary red clay indieated that liming increased the yield of barley in 2-3 times, but the respond of rice to liming was not obvious. The increase of yield of barley may be mainly related to the raising of pH value of acid soil, the elimination of Al-toxicity, the improvement of growing environment and availability of P-fertilizer as well as markedly promoting of the absorption of P and K by barley. However, due to strong of rice adaptability to soil acidity, liming will depress P-absorption of rice under submerged condition. Therefore, the lime should only be applied to some upland crops as barley. It is suggested that the amount of lime far barley should be applied to neutralize soil pH at about 6.0. In any case, excesively liming is undesirable.

Abstract:This paper deals with the physical, chemical, micromorphological, and mineralogical properties of thirteen profiles of soils developed in the southern subtropical region and the central subtropical region in Fujian. The dcgree of allitic weathering, selection of indices for dividing soil groups, and classification of these soils are discussed. These soils are all in the moderate allitic stage, but with more or less different degrees of development. As for the allitic soils which have not yet deeply weathered, kaolinization can reflect the soil development degree to a great extent. Thus, the average kaolinite contents of clays in B horizons have been chosen as the main index for dividing soil groups, and the average silica-alumina ratios of clays in these horizons as the accessory index. All the soils have been divided into two groups. The first is the group of lateritic red earths, of which the average kaolinite contents of clays in B horizons are more than 70%, or the average silica-alumina ratios of clays in B horizons are less than 2.10 when the kaolinite contents are between 60% and 70%. The second is the group of red earths, of which the average kaolinite contents of clays in B horizons are less than 60%, or the average silica-alumina ratios of clays in B horizons are more than 2.10 when the kaolinite contents are between 60% and 70%. The distribution of the two groups soils does nor entirely conform with the zonality.

Abstract:Migration of Cu and Zn in soils derived from basalt in Zhejiang Province occurs in their soil forming process. The amount of migration of Cu is larger than that of Zn. However the influence of the migration of these elements on their total contents is less than that of the geochemical difference of parent riaterials. Cu and Zn contents in the surface soil are higher than those in subsoil, and those in the soils with a higher altitute are higher than those in the soils with a lower altitute. The effect of pH is insignificant.The ratio of amorphous Cu to total Cu in the soils with similar allitic process increases with the increase of the altitute at which the soils are located, i.e. there is significant difference in the ratio among the red earths, yellow-red earths and yellow earth. However, the content of amorphous Cu tends to be decreased with the intensification of weathering and eluviation proceses. All these may be used as factors for soil classification and evaluation of soil fertility.

Abstract:The paper deals with the genetic characteristics of lime concretion black soil and albic soil in North Jiangsu Plain, the features of association of the soils and their relation to ecological environment. This work was made through studying formation of lime and Fe-Mn concretions in the two soils. The results showed that the genesis of the two soils were deeply influenced by ancient ecological environment. It was a common characteristic of the two soils that periodical alternation of oxidation-reduction resulted in the leaching of Fe and Mn and the formation of Fe-Mn concretions. The formation mechanism of the small Fe-Mn concretions (less than 2-3 mm) was different from that of large ones(greater than 5-7 mm). Lime concretions originated from the ground water were the result of regional geochemical sediutenration. So, they occured not only in the two soils but also in the buried palesols of the Quaterary deposits in the region. Finally, the soil association existed in this region was affected by both recent and ancient enmronments.

Abstract:This paper deals mainly with the genetic characteristics and vertical distribution of the sort of Mt. Jiuhua which is located in Qingyang County of Anhui Province. The basic belt of soil in the region of Mt. Jiuhua is that of red earth, the soil sequence from the mountain foot going upwards is in the order of red earth-mountain yellow browns arth-mountain acid brown earth-mountain shrubby meadow soil.

Abstract:在半干旱地区,水是制约农作物生产的最重要的因素之一。研究土壤水分动态,掌握土壤水分变化规律是在这一地区蓄水保墒提高水分利用效率的前提条件。对土壤水分动态的研究,国内外学者已做了许多工作,但以计算机作为工具来研究农田土壤水分动态的报道还不多见。

Abstract:宜昌地区位于湖北省西南部,地跨江汉平原和鄂西山地,过渡性的位置和复杂的自然条件,导致土壤有效锌含量变化很大。在全区430万亩耕地中,严重缺锌土壤达208万亩,占总耕地面积48%,是粮食生产上新台阶的限制因素之一。