Abstract:The paper deals with distribution, some genetic characteristics and taxonomic classification of main Vertisols in China. Eleven profiles from main areas of Vertisols in China were studied. The research content included: (1) morphological features, physical and chemical properties, abundances of macro-elements and trace-elements, iron and manganese oxides and clay minerals of main soil genetic horizons; (2) chemical and mineralogical composition of iron-manganese concretions and calcareous concretions etc.The results show that Vertisols and Vertisol-type soils in China are distributed widely front tropical zone, subtropical zone to warm temperate zone, which could be roughly divided into three areas: (Ⅰ) tropical Udic Vertisol area, including two pell clay soil regions in depressed lowlands of basalt tablelands of the northern Hainan Island and Leizhou Peninsula; (Ⅱ) sub-tropical Udic Vertisols area, including three pellic and chromic clay soil regions in lowlands, basins and river terraces of southern China, Yunnan-Guizhou Pleteau and Sichuan basin; and (Ⅲ) warm temperate zone Aquic Vertisol area, including three black clay soil regions in low-lands of Huaibei Plain, Shandong Peninsula Plain and Nanyang Basin. Their soil-forming factors are characterized by the alternation of wet and dry climate, low and flat terrain, parent material with abundant bases and heavy texture. The area of the soils was estimated at about one percent of the total land area of China.

Abstract:The micromorphology of six Vertisols (two black clay soils from Xincai of Henan Province, two pell clay soils from Zhangpu of Fujian Province and two chrom clay soils from Guangxi Zhuang Autonomous Region) and two other related soils from Fengqiou of Henan Province and Zhangpu of Fujian Province were studied.The voids, peds, optically oriented clays and plasimic fabrics in the Vertisols are markedly related with clay contents, clay mineralogy and shrink-swell potential, according to the macro-, micro- and submicromorphological studies and the wetting-drying and shrink-swell experiment. All the six Vertisols have granular and fine angular blocky structures in surface layers, and have medium and coarse angular blocky structures in the "vertic horizons", of which the secondary and tertiary peds are well developed, especially in the pell clay soils. The voids in thin sections of all the six Vertisols are mainly the fissures and hairline cracks ranging from 0.005 to 5 mm in width, especially in the "vertic horizons". The fibrous form of optieally oriented clays are formed in all horizons of pell clay soils and in the surface and sub-surface "black" layers of black clay soils. However, they are not found in the chrom clay soils and in the lower horizons of black clay soils, as the high content of carbonates could confine山e rearrangement of clays in place. The higher the content of clays, and the more the expansive clays and the greater the shrink-swell potential are in the Vertisols, the more and better developed the fissures, structures and oriented clays have been formed.

Abstract:Effects of ionic strength of electrolyte solution and narrue of canon on phosphate desorption in some variable-charge clay minerals and soils were studied. It was observed that Ca²⁺-saturated montmorillonite, kaolinite and clay colloid from red soil sorbed more Phosphate than Na⁺-saturated samples, but much less phosphate than Al³⁺-saturated samples. Such differenct was more significant for montmorillonite than kaolinite or soil clay, suggesting that cation bridge mechanism was in action. The bonding strength of formed surface complex depended on the ability of canon to neutralize the negative change on the solid surface and its chemical affinity for phosphate ion. With increasing valence of the canons from Na⁺ through Ca²⁺ to Al³⁺, decreasing phosphate was desorbed at the same adsorption saturation for all tested samples, especially for montmorillonite, due to stronger electrostatic attraction of the cation for both negatively charged surface and phosphate ion.

Abstract:The experimental apparatus which is applied to study the swelling of clay has been designed and made. The experimental apparatus is mainly composed of five parts which are(1)nitrogen tank, (2) gas valve, (3) pressure gauge, (4) temperature control box, and (5) pressure membrane system. The fifth part is made of polymethyl methacrylate and consists of two chambers, i.e.,upper chamber and lower chamber in which two Ag-AgCl electrode are respectively installed to indicate the equilibrium.The swelling of clay in the upton montmorillonite clay system with overlapping electric double layer was studied at 25℃ by using the method of Ag-AgCl electrod to set the equilibrium. The clay suspensions with different electrolyte concentrations were made up by montmorillonite and NaCl solution of given concentration. When the experiment began, the given pressure was applied to the clay suspension surface in upper chamber by nitrogen gas. When the difference of millivolt between two Ag-AgCl electrode did not vary with time, the equilibrium had been obtained. The experimental data, such as swelling pressure, P, distance between two clay plates, λ, Cl^- concentration is clay cake of the upper chamber and in the bulk solution of lower chamber were measured. The experimental results shown that the swelling pressure, P, was the exponential function of the distance between two clay plates, λ, and the variation of swelling pressure with the distance between two clay plates could be described by erapirical equation.

Abstract:The weathering degree of feldspar in 3 sets of profiles of red and yellow soils was studied. In <2 micron fractin of red soils derived from basalt, the content of feldspar is <6g kg^-1. In 2-10 micron fraction, Xuwen laterite and Zhangpu lateritic red earth contain<4 g kg^-1 feldspar; however, Chengxian red earth contains<7g kg^-1 Ca feldspar, and other feldspars are 18-51g kg^-1. In 10-50 micron fraction, besides Chengxian red earth still contains more feldspar, K and Na feldspars in surface horizon of Zhangpu lateritic red earth are> 29g kg^-1. For red soils derived from granite, the contents of feldspars in <2 micron fraction are similar to that of red soils derived from basalt In 2-10 micron fraction, Guangzhou lateritic red earth contains <2g kg^-1 K and Na feldspars, Qianshan red earth 27-49g kg^-1, Huangshan red earth 42-84g kg^-1, but the content of Ca feldspar for all the soils is less than 8g kg^-1. The contents of feldspars in 10-50 micron fraction are similar to that in 2-10 micron fraction, but the amounts of K and Na feldspars in Qianshan and Huangshan red earths are higher. In<2 micron fraction of mountain yellow soils derived from granite, K and Ca feldspars are less than 5g kg^-1 and Na feldspar is usually more than 10g kg^-1; in 2-10 micron fraction, Ca feldspar is less than 7g kg^-1, but K and Na feldspars are 5-100g kg^-1; in 10-50 micron fraction, Ca feldspar is less than 9g kg^-1, K feldspar varies greatly between 14-217, and Na feldspar changes from 31 to 170g kg^-1.

Abstract:Mangshan is a granitic mountainous region which is located at 24°54'-25°03' north latitude and 112°43'-113°20' east longitude. The altitude of the highest mountain peak is 1902 meters. The examined soil samples were collected fron different altitudes. The layer-silicate minerals and the oxides of clay-size minerals of fifteen soil samples in five soil profiles on the north slop of the Mangshan Mountains in Hunan Province were studied by X-ray dif fraction analysis and chemical selective solvent extraction analysis respectively.

Abstract:In this study, direct current (DC) conductivities in the system which was composed of ahe clay fraction(<2 p) of variable charge soil and electrolyte solution with a concentration of 0.35×10^-4-1.3×10^-4 mol/L were measured within the range of 5-50℃. The results showed that heated conductivity dispersion could be used for investigating interactions between ions and the clay fraction of soils. The temperatures at turning points on DC conductivity-temperature curves varied with the content of water, kind of electrolytes, and type of soils. At the same content of water, the temperatures at turning points for the sysrem of red earth containing different electrolytes were in the sequence of CaCl₂ > Na₂SO₄ > KCl > Ca(NO₃)₂ > NaNO₃. The temperatures at turning points for latosol system were apparently higher than chose for red earth system. The difference in temperatures at turning points is interpreted in terms of the strength of the interaction between the ion and the clay particle.

Abstract:Investigation on the soil humus under different forest types indicated that: (1) In those years both litter and C/N ratio of surface soil were the highest in the pines tabulaeformis forest lands, but the lowest' in the Hippophae rhamnoides lands. The C/N ratio of surface soil was positively correlated with the age of forest and the C/N ratio of litter, but negalively correlated with the ash content of litter. (2) The average contents of humic acid, humin, fulvic acid in the soil profiles decreased in the following sequence: Betula platyphallo forest land>Quercu Liaotungensis land>Quercu Liaotungensis+Popular davidiana forest land>Populus davidiana forest land>Hippophae rhamnoides forest land>Pines tabulae-formis forest land, i.e. broad-leaved arbon forest land>shrub forest land>coniferous forest land; but the average content of humin was in an opposite order. (3) The aromaticity of surface soil of the Ziwu Mountains declined in the following order: Betula platy phalla forest land>Quercur Liaoturtgensis forest land>Quercu Liaotungensis+Populus daviana forest land>populus daviana forest land>Pines tabulaeformis forest land>Hippophae rhamrtoides forest land; whereas that of the Liupan Mountain was in the order of Populus davidiatta forest land>Quercus Liaotungensis forest land. The profile humic acid aromaticity of the Ziwu Mountains and the Liupan Mountain decreased in the following sequence: three layer>two layer>one layer.

Abstract:Field and sand culture experiments were conducted to study varietal difference of rice plants in response to N levels and its physiological mechanisms. The results obtained show that at low N (mediately deficiency) and high N (sufficient) levels the biomass of the top and grain yield of the varieties tested at main growth stages decreased in the order: Shanyou 64 > Shsnyou 6 > Zheli 1 > Xiushui 48. The greatest difference was found between the hybrids and the conventional varieties, especially at a low N level. The results also show that the rice variety which could obtain higher yield at a low N rate had a greater potential of absorbing and utilizing N from the soil with following characteristics: 1) a well developed and vital root system with a greater root volume and distribution density, and a higher affinity to NH₄⁺, i.e. with a smaller Ko value; 2) greater activities cf the key enzymes involved in the assimilation of NO₃^- and NH₃ and photosynthesis in the leaves. All these physiological characteristics may be used as the indices for identifying and selecting N-efficient variety or genotype.

Abstract:This paper deals with sixteen typical calcareous soils (pH 8.09-8.69 and CaCO₃, content 2.95-15.8%), i.e. sierozem, chestnut soil, dark loessial soil, yellow cultivated loessial aoil, old manaial loessial soil, black loessial soil, and yellow fluvoaquic soil sampled, respectively, from Gansu, Shanxi, and Henan provinces of China. The scheme developed by Jiang Baifan and Gu Yichu was employed for inorganic-P fractionation and the results show that the total amount of inorganic-P in the calcaerous soils tested is 550 ppm on average, in which Ca₂-P, Ca₈-P, Al-P, Fo-P, O-P, and Ca₁₀-P account for 1.34%, 9.91%, 4.27%, 4.40%, 10.9% and 69.1% respectively. The regression analyses between different forms of inorganic-P and P uptaken by plants indicate that the availability of Ca₂-P is surely recognized, and the P uptaken by plants is mainly Ca₂-P; Ca₈-P, Al-P, and Fe-P are also available forms of inorganic-P; while Ca₁₀-P is unavailable.

Abstract:This article present a brief review on liming of paddy soils. It covers the effects of liming and process of waterlogging-drainage. on pH, Eh and reducing materials of paddy soils; and the effects of Liming on soil microbe, orkanic matter, nitrogen, phosphorus, potassium, microe-lements transformation, properties of soil physics and the growth of upland crops (such as barley, wheat) and rice in daddy field.From above, it could be concluded that litne is not necessary for rice production when soil pH is over 5.6, but when below 5.5 lime may be applied in comuination with apolication of organci manures before transplantation with consideration of soil buffer capacity. It's best to apply lime to upland crops in the rotation of paddy field.

Abstract:Water and soil losses bore a close relationship with the rainfall and the soil moisture before raining. The critical rainfall intensity for sloping field to produce surface erosion was 4 mm/10 min, and the critical rainfall 12.5 mm. The soil loss doubled as the rain-type rose one level from moderate rain to cloudburst soil erosion appeared.notably in direct proportion to erosive rainfall. The amount of runoff was in direct proportion but the quantity of soil loss in inverse proportion to 0-30 cm soil moisture factor before raining.

Abstract:土壤的一切生物化学过程,都是在酶的参与下进行。许多研究表明,土壤酶能积极参与陆地生态系统中的物质循环及能量转化,是表征土壤肥力的重要指标之一^[4-6]。因而,研究土壤酶活性的季节动态变化,对于了解不同混交林林地土壤的生物活性及肥力状况,有着重要意义。

Abstract:发育在冲积平原上的土壤,土体中夹有粘土层是很普通的现象。1987年在滨海平原110个土壤剖面调查中,发现粘土层以不同厚度和层位存在时,土壤表现出不同的盐渍状况,该地区粘土层表居很普遍。我们曾对粘土层在浅、中、深三个层位的5、15、30厘米三个厚度对水盐运动的影响作过研究,结果是枯土层对水盐运动的抑制作用随粘土层厚度 钓增加、层位的升高而加强^[2-5]。但是实际调查使我们感到有必要进一步研究土体中粘土层对水盐运动的影响规律,通过毛管水的上行运动的研究,了解粘土层的作用实质。