Abstract:In this paper both the absolute and relative contents of fixed NH₄⁺ in soils of soil zones except the alpine and subalpine soil zones of China are presented, the NH₄⁺ fixation capacity and the availability of fixed NH₄⁺ of major soil groups are indicated. The origin of fixed NH₄⁺,the factors affecting the content of fixed NH₄⁺ and the ability for fixing NH₄⁺ of soil, and the significance of NH₄⁺ fixation and defixation in the internal cycle of soil N are disccussed. The content of fixed NH₄⁺ in soils of yellow brown soil zone, as a whole, is the highest, being 257 mg/kg, while that of latosol zone is the lowest, being 48 mg/kg. On average about 15% of N to depth of 20cm for the cultivated soils as a whole of China was estimated to occur as fixed NH₄⁺.Of the native fixed NH₄⁺,dependent on both the kind of parent material (rock) and the degree of weathering of the soil, from 3% to 20% can be utilized by plant. The NH₄⁺ fixation capacity of soils of yellow brown soil zone is also the highest, while soils of latosol zone, lateritic red soil zone, grey brown desert soil zone and brown desert zone as well as some soils in the red soil zone are unable to fix added NH₄⁺.Based on the differences in the amount of fixed NH₄⁺ and its contribution to soil N pool, as well as in the ability for fixing NH₄⁺,soils in China except those in the alpine and subalpine soil zones are grouped into 10 soil regions.

Abstract:Fluxes of methane emission from the year-round flooded paddy field and tillage-cropping systems effects were investigated for two years from 15 May 1995 to 15 May 1997 in field in Southwest China. The results showed that fluxes of methane emission from the year-round flooded paddy field during the rice growing seasons varied from 0.47 mg/m²·h to 171.12 mg/m²·h, and averaged 33.91mg/m²·h. But, it was the most important and the most remarkable that there were 2.51~54.42mg/m²·h of methane emission fluxes, averagely 13.24mg/m²·h during the nonrice growing season from 250 days to 280 days yearly. So, the year-round flooded paddy field with 165.82g/m²·a of methane emission flux was the one of largest methane emission flux in varieties of paddy fields in the world now. The ridge culture (semilate rice) could reduce yearly methane emission fluxes in rice paddy field by 3.36% in 1995 and 33.53% in 1996 compared with the year-round flooded paddy field. The mean fluxes of methane emission in the paddy fields under the ridge culture (rice-wheat) system and under the paddy-upland (rice-wheat) rotation system during the rice growing seasons were lower than those under year round flooded paddy field, and yearly fluxes of methane emission only accounted for 36.7% and 11.96%-34.27% of those under year-round flooded paddy field at the sametime. The ridge culture (rice-wheat) system and the paddy-upland (rice-wheat) system were one of the most effective methods for reducing flux of methane emission from the year-round flooded paddy field in Southwest China.

Abstract:Effect of fertilization on active C (C_A), microbial biomass C(C_MB),mineralizable C (C_M) and C pool management index (CPMI) in different soils were examined. Results indicated that among those studied soils, soil C_A, C_MB,C_M and CPMI were the highest in paddy soil, the second in yellow brown soil, the third in red soil and the lowest in Cao soil. Effects of different treatments on C_A, CPMI, C_MB and C_M were organic manure>organic manure+NPK>reference>NPK>CK, organic manure>organic manure+NPK>NPK>reference>CK respectively. In raising C_A,C_MB,C_M and CPMI, effects of different organic fertilizer types and application were rice straw, green manure better than farmyard manure, high application better than conventional application. Compared 5-y fertilization with 10-y fertilization, CPMI in Cao soil under organic fertilizer and organic fertilizer+NPK treatments increased, while CPMI decreased under NPK and CK treatment Correlation analysis showed: CPMI was well related to total C, total N, microbial biomass C and N, available N,P and K in these soils and sensitive to agricultural measures, which indicated that it is practical to assess soil C pools under different management practices using CPMI.

Abstract:Chestnut soils formed at 6000-8000 years ago are a typical steppe soils in the alternative belt of semiarid agriculture and animal husbandry. The chestnut soils on basalt and sandy sediment have undergone accumulation and decomposition of organic mater, illuviation and leaching of carbonate, migration and enrichment of elemental oxides, as well as deposition of aeolian sand with time. Uder the influence of human activities, such as reclamation and planting crops, overgrazing, the physical and chemical properties of the soils have been getting deterioration and soil degradation occurred in the course of soil evolution since the last more than two hundred years.

Abstract:Characterization of magnetism and iron oxide minerals for Quaternary red earth was investigated by mineral magnetic measurements, X-ray powder diffraction and transmission electron microscopy. The data indicated that there were significant differences in magnetic susceptibility(χ),frequency dependent susceptibility (χ_fd), anhysteretic remanent magnetization, saturation isothermal remanent magnetization (SIRM) and demagnetization parameters between homogeneous horizon and reticular horizon for red earth.

Abstract:X-ray diffraction and selective chemical extraction methods were used to investigate the types of manganese minerals in iron-manganese nodules of several soils in China. The changes of relative intensity of X-ray diffraction patterns were studied before and after chemically selective extraction. It was found that lithiophorite was a common manganese mineral in all tested iron-manganese nodules with high degree of crystallinity. Todorokite, however, was predominant manganese mineral of iron-manganese nodules in cal-aquic Vertisols of Shandong province (No.5-4). The iron-manganese nodules of arp-udic Luvisols (No.2-1, No.4-1) in Hubei province contained birnessite and vernadite. Moreover, hollandite was found in iron-manganese nodules of alt udic Ferrisols in Yizhang, Hunan province (No. A), arp-udic Luvisols (No.4-1) in Zaoyang, Hubei province and cal-aquic Vertisols (No.5-1) in Shangdong province. There were a few of coronadite in iron-manganese nodules of alt udic Ferrisol in Guiyang, Hunan province (No.1-1). The types and amounts of manganese minerals in soil iron-manganese nodules were related to conditions of soil materials and environments.

Abstract:The kinetics of Hg volatilization indicated that humus (including fulvic acid, brown humic acid and grey humic acid) have either suppressing or activating effect on the volativity of mineral bound Hg. Initially the volatilization of mineral bound Hg is depressed and then is promoted, but eventually it turns into a stable state. The effect is characterized by long term and gradual change. Various kinds of humic acids have different rate and intensity to depress or promote the volatilization of mineral bound Hg. The type of mineral bound to the Hg is the internal factor that will determine the progress of the volatilization reaction.

Abstract:Measured Koc values of 592 chemicals collected from literature were used to develop a sorption coefficient estimation model based on fragment constants plus structural correction factors. The results showed that Koc of organic chemicals can be well estimated based on the fragment constant modeling. For the 592 chemicals, the coefficient of determination of the regression model was as high as 0.9696 with a mean absolute error of 0.37 log-unit.

Abstract:To predict water flow, knowledge of soil hydraulic properties is required. Horizontal infiltration of water into soil columns can be observed in order to determine hydraulic properties. Required physical and mathematical analysis of the observation is based on an integral solution of Richards'equation. The parameters of the soil water characteristic curve are estimated by the observed characteristic length of wetted zone and sorptivity. Unsaturated hydraulic conductivity is estimated from the parameters determined in the soil water characteristic curve and the measurement of saturated hydraulic conductivity. Three soils ranging from sandy loam to clay loam are included in this research. Soil water characteristic curves for the three soils estimaed by the infiltration method are in good agreement with measured soil water characteristic curves. Unsaturated hydraulic conductivity, estimated by the infiltration method for the sandy loam, also compares well with measured values. To further check the method, water content of the three soils are calculated through the numeric method and the integral method based on the calculated hydraulic parameters. The calculation results indicate that the method is accurate.

Abstract:Based on the long-term experiments of different cutting frequency of natural vegetation (Imperata cylindrica var. major), in red soils of south of Hunan Province, the changes of contents of organo-mineral complex, acidity and Fe, Al oxides were studied. The results showed that the changes of the soil acidity were not any regular, but the contents of organic matter, organo-mineral complex, exchangeable K, amorphous Fe and Al, complex Fe and value of loosely combined/tightly combined, activation degree of Fe in the soil had a tendency of increasing, whereas the contents of exchangeable Na and Ca, free Fe and Al were decreased relatively when the cutting frequency treatments from one year to 6 years.

Abstract:Based on the results of long-term (10 years) field experiments of potassium (K) application under three cropping systems including rape seed-early rice-later rice, middle rice-wheat, cotton-wheat in Hubei Province, the effect of long-term K application on the yields and profits of the crops is indicated in this paper. The influence of long-term K application on K contents and status in soil is also discussed.

Abstract:From a three-year fix-location field experiment, the research work on the Se content of paddy soil and effect of foliage spray of Se-compound on the Se content of rice in Jiashan plain, the author found that:(1) The water soluble Se of paddy soil in Jiashan plain, resulting from the low contents of the total Se of paddy soil, was below critical value (0.01μg/g). It was significantly related to parent material and geomorphological factors etc; (2) The absorption of Se by rice was restricted by low water soluble Se of paddy soil, resulting in the rice Se reduction in this region. The average of rice grain Se was lower than the normal food Se contents (0.040-0.070μg/g); (3) The above-ground organs of rice contain different amounts of Se: the Se contents in the bran and the straw were higher than those of both early and late rice grain; the Se contents in the grain, bran and straw of the early rice were lower than those of the late rice, respectivey; (4) By spraying 20μg/g Se compounds during the different rice growth stages the Se contents in the grain, bran and straw were increased, and the Se contents of the grain finally met normal standards of Se contents in food. The best time to spraying Se-compound was at the full spik stage,and effect on early rice is better than that on late rice.

Abstract:The properties of adsorption-desorption, adsorption heat, and hysteretic desorption of boron effected by temperature in brown-red soil (9701), yellow-brown soil (9702), and calcareous alluvial soil (9703) collected in Hubei Province of China have been studied. The results showed that the adsorbed boron was more in 25℃ than that in 40℃,r. e., boron adsorption reaction was exothermic. The boron adsorption heat of 9701, 9702, and 9703 calculated with equilibrium constant of the Langmuir adsorption equation in 25℃ (K₁) and 40℃ (K₂) were -16.4,-15.6, and -22.6kJ/moL, respectively. These values were within the range of chemical adsorption heat, and it was testified in thermodynamics that boron adsorption in soil is mainly a kind of chemical specific adsorption. In comparison with 25℃,that hysteretic desorption of boron in the experimental soils was higher in 40℃,the hysteretic coefficients of boron of 9701, 9702, and 9703 were enhanced to 67%, 21%, and 62%, respectively. Being corresponding with the properties of soil boron adsorption-desorption, the desorption ratio of added boron of 9701, 9702, and 9703 in the summer were lowed by 38%,19%, and 7% than in the spring, respectively. These may explain that lack of soil boron in the summer was caused by increase of boron hysteretic desoiption in soil in higher not by decrease of boron adsorption in soil.

Abstract:2-year-old potted Starkrimson/M. hupenensis Rehd. apple trees were used as materials in the experiment Effect of potassium on water use efficiency and relevant parameters of plants under conditions of different soil water status was preliminarily studied. The results showed that under the condition of adequate soil water content, stomatal conductance (Gs),photosynthetic rate (Pn) and transpiration rate (Tr) were all improved for trees applied potassium fertilizer, which resulted in the reduction of WUE because Tr was increased more than that Pn was. However, under the condition of soil drought, WUE of trees applied potassium fertilizer was apparently promoted as compared with contrast ones. WUE of trees with different potassium level was increased in the order: high K > medium K > low K For treated plants under soil drought, as a result Gs and Pn were enhanced but Tr lowered, the improvement of WUE was due to both the increase of photosynthetic rate and the decrease of transpiration rate.

Abstract:The soil composition of aggregate and its stability, in Cransu Jingtai electricirrigating area, were studied in this paper. The results showed that the content of aggregate is low and its stability is poor. When moistened, much a large portion aggregate is detached. Clay has the greatest influence upon aggregate and its stability, this means that clay currently is the most important aggregating agent the role of CaCO₃, as aggregating agent, is the second and that of organic matter is the last because of its low content. However, the influence of organic matter upon aggregate's stability is greater than that of CaCO₃. Soluble salts make the content and stability of aggregate decreased. The study of microaggregate demonstrated that nearly all of particles <0.005mm are distributed in microaggregates >0.01mm, indicating that clay <0.005mm is aggregated perfectly, and structure coefficients of nearly all soils reach one handred percent. The effect of CaCO₃ on clay's aggregation is significant but organic matter plays minor role. Soluble salts has the trend detaching clay.In point of structure state and factors affecting its stability, soil wind erosion,low organic matter content and soluble salts accumulation were main reasons responsible for structure degeneration. The improvement and reconstruction of soil structure must go on with increase in organic matter, avoiding salinization and wind erosion and the improvement of ecological surroundings.

Abstract:土壤水力性质包括土壤水分特征曲线(它表明了土壤的基质势h与土壤水分含量θ之间的关系)θ(h)、非饱和水力传导率K和扩散度D。由于土壤的这三种水力性质可以通过关系式K=Ddθ/dh联系起来,因此,它们当中只有两个是独立的。

Abstract:高黎贡山位于滇西北中缅边境的横断山地区。由于其多种多样的森林类型、生物资源,早已引起世界性的广泛关注。高黎贡山山体宏大,上半部是国家级自然保护区,分布 着多种类型的原生植被和丰富的生物资源;下部(1500m以下)有村庄分布,近10年来,由于人口激增,森林大量被砍伐、放牧和开垦成农田或人工纯林,形成片状分布的次生林,山底部的次生林基本上已被砍光。植被的破坏导致生态环境恶化,同时,也对自然保护区森林和生物资源产生了很大的威胁。

Abstract:由于重金属在土壤中的难移动性和污染危害的长期性,有关重金属在土壤中化学行为的研究受到重视^[1]。重金属铜在土壤环境中既有植物营养问题,又有土壤污染问题^[1,2]。研究土壤铜的形态区分与转化、作物吸收积累与反应规律,有利于确定土壤铜的环境容量和铜污染土壤的改良方法^[1,3]。

Abstract:矿山开发不仅直接造成大规模土地破坏,而且开发过程中产生的废弃物(尾矿砂、矿石等)需要大面积的堆置场地,从而导致矿区土地生态系统的严重破坏。因此,矿区生态恢复日益受到世界各国的广泛关注^[1-3]。由于植物生长对土壤条件有一定的要求,土壤条件现状研究就成为生态恢复工作的首要任务^[1,4,5]。