Abstract:A study was conducted to extract relationships between terrain factors and soil properties by clustering terrain factors based on the fuzzy set theory.Similarity of each pixel to the typical ones was obtained from the classification results,with degrees of similarity referred to as fuzzy membership.Then,a continuous soil horizon thickness distribution map was drawn with the aid of ARC/in of software based on samples collected at the area with high value of fuzzy membership and population of the similarity model using the linear and additive weighting function.Comparison of the predicted value set from the map with the independently collected field sample set showed the derived soil map achieved 82% of accuracy.Further investigation showed that the model worked well in the area of low altitude,well-developed soil,thick soil horizon,stable surrounding for soil formation.The new approach was found to be higher in efficiency and accuracy of soil mapping,lower in mapping cost,and more capable of demonstrating microregional variance and accommodating higher information load for mapping.Hence,it is a feasible new method worth extrapolating in soil survey and mapping.

Abstract:Soil wind erosion refers to the process of loose soil substances being blown up and carried away by wind and de posited somewhere else,and the process of land surface being abraded by the blown up soil particles.Its essential is the process of fine soil particles and nutrient matters in the surface soil being blown away by wind.In China the total area of lands exposed to wind erosion and desertification exceeds one half of its total land area.Those lands are distributed mainly in the arid and semi arid regions in North China.The Hexi Corridor in Gansu Province is one of the areas that are subjected to most serious desertifi cation,because of its long term conventional tillage and prevalence of northwester.A wind tunnel experiment was designed to study effects of conservative tillage in winter wheat cultivation on wind blown mass,critical wind speed,wind velocity profile and roughness of land surface and their relationships.Results show that all the treatments were higher than CK (SWT,spring wheat with conventional tillage) in wind blown mass and critical wind speed.Wind blown mass showed a power function relationship with wind speed and the wind speed of 16 ms^-1 was the turning point from slight wind erosion to serious wind erosion.Within the height of 5~50 mm above the land surface,the rise of wind velocity with height in Treatment NTS (no tillage with stubble retention (NTS) and Treatment NT (no tillage with no stubble) was slower than in Treatment TIS (conventional tillage with stub ble incorporated) and Treatment T (conventional tillage),and height and wind speed formed an exponential function in all the treatments.Roughness of the land surface varied significantly between Treatments NT,NTS and SWT at 0.01 level,but it did not between Treatments TIS and SWT.Significant negative relationship was observed between wind speed and roughness,and al so between crit ical wind speed and roughness.

Abstract:The mapping of heavy metal distribution is usually associated with certain uncertainty that needs to be considered in decision making for heavy metal pollution management.The uncertainty in prediction of heavy metal contents at unsampled lo cations is part icularly important because such uncertainty can be propagated into subsequent modelling or decision making process and has fundamental impacts on ultimate results.Based on the Cu content data of a total of 547 topsoil (0~15 cm) samples in Zhangjiagang City,the sequential indicator simulation (SIS) were applied to perform a conditional stochast ic simulation in this study to quantitatively assess the uncertainty of mapping total Cu content.Results show that prediction of the spatial pattern of soil Cu fluctuated the most in the eastern and central northern parts of the study area,where intensive agriculture and metallurgic and electronic enterprises dominate and the total Cu contents were high,and the least in the southern part,where the total Cu contents were low.The pattern simulated with SIS did not show any smoothing effect.With a given threshold of Cu content,SIS can quantitatively assess both local uncertainty and spatial uncertainty of Cu content that is greater the threshold.

Abstract:A rapid,simple and lowcost method,based on the technology of reflectance spectroscopy,for measuring soil heavy metal contents is needed for monitoring and remedying heavy metal contaminated soils.Soil samples were collected from a Cu-Cd contaminated area in the vicinity of a copper smeltery in Guixi,Jiangxi Province,to explore relationships between visible-infrared reflectance spectra and contents of Cu,Zn,Pb,Cd,Cr,Co,Mn,Ni,and Fe in the heavy metal contaminated soil and their mechanisms.Results show that Cu (ranging from 66.7 mg kg^-1 to 387 mg kg^-1) and Cd (from 0.36 mg kg^-1 to 6.02 mg kg^-1) were highlyenriched in the soil,and reflectance spectra of the soil samples were significantly related to contents of heavy metals in the soil,with the highest correlation coefficient of Cu being-0.87,of Pb,Zn,Co,Ni and Fe being> 0.80,and of Cr,Cd and Mn being> 0.70.Derivative spectra are applicable to extraction of information of heavy metals in soils and bands combination may significantly improve their correlations.The relationship of Cu with reflectance spectra was affected by organic matter;of Zn,Pb,Co,and Ni,by silicate minerals and ferriferous-manganese oxides;and of Cr,by both organic matter and clay minerals.

Abstract:Based on elaborate analysis of pollution sources of the soil and a better understanding of the complexity of the soil pollution,an early warning system for ecoenvironment quality of farmland was established in light of the particularity of the research site (suburb).This system consists of three models,namely,evaluating model,forecasting model,and early warning model.The system monitors variation of soil pollution intensity as is influenced by the socio-environmental system and predicts trends of the variation of soil environment quality.Based on this understanding,the warning system was applied as test-run to the farmland in the suburbs of Zhengzhou city.The following findings were obtained.(1) The ecoenvironment quality of the farm-land in the suburbs of Zhengzhou has experienced a process of variation from rapid deterioration to relatively the worst and now to getting better,which implies that intensity of the stress of the socio-environment on soil environment has also followed a similar process,i.e.rising-the strongest-declining.(2) In general,the ecoenvironment quality of the farmland in the suburbs of Zhengzhou is not optimistic.It is,therefore,essential to exert overall control of all the factors that affect soil pollution,reduce external environment's stress on farmland soil environment,implement the work of early warning and prevention of soil pollution,and finally realize sustainable use of farmland soil.

Abstract:Generally,in an experiment oriented to determine soil water retention characteristics,just one soil sample is used continuously.During the experiment,the soil would not change much in organic mater content,clay mineral type and cation exchange capacity,but would in bulk density because of hydraulic and mechanical pressures in combination.Therefore a hypothesis is put forth that soil water retention characteristic should be a surface consisting of mass water content,pressure head and bulk density instead of a curve of two variables,pressure head and water content.In this study,two models to fit soil three-variable characteristic surfaces of different soils were proposed based on the Brooks-Corey soil water retention curve model.Ad-vantages,disadvantages and application conditions of the two were illuminated.In addition,soil three-variable surfaces measured for packed soil samples through centrifuging and controlling bulk density using paraffin material were used to verify the proposed models.Results show that the hypothesis of three-variable characteristic surface is reasonable.The two proposed models based on the Brooks-Corey power function fit the measured data well with determination coefficients being greater than 0.94.Although Model Ⅰ performed a bit better than Model Ⅱ,the latter Ⅱ seems to be superior in application because it contains two additional parameters with definite physical meaning.The findings of this research could be cited as a new method in verifying the effect of bulk density on soil hydraulic parameters.

Abstract:Transport behavior of applied chemicals in soil is essential for evaluating their potent ial leaching to groundwater In this study sorption of glyphosate to a sandy. Fluvo aquic soil as affected by pH was determined using batch technique and its transport behavior in the soil as affected by different application rate of phosphate investigated through a miscible displacement experiment under soil water saturated conditions and constant flux. Results show that the glyphosate sorption decreased with increasing pH,particularly when pH rose from 4 to 6 All measured breakthrough curves (BTCs) exhibited different extent of asymmetry with sharp adsorption and slow desorption fronts,the lower the glyphosate application rate,the more distinct the asym metry.Ageneral trend of phosphate application inhibiting transport of the chemical was observed,while the trend was not consis tent with the application rate of phosphate For example,when application rate of glyphosate was 500 mg L^-1,the peak glyphosate concentration in efflux was 459 8 mg L^-1 in Treatment P0,and 147 3 mg L^-1 and 373 6 mg L^-1 respectively in Treat ment P1 and P2. It is probably because application of phosphate leads to decrease in pH and phosphate occupy adsorption sites in the soil preempt ively.

Abstract:A study on movement and redistribution of water and salt in soil in relation to emitter discharge rate was conducted through indoor simulation tests in soil columns.Results show that depending on emitter discharge rate,the wetted front at the meeting interface of waters from two emitters appeared to be either elliptical or circular.High emitter discharge rates accelerated horizontal movement of the water,resulting in greater horizontal dispersion rate than vertical infiltration rate.With decreased emitter discharge rate,the distance of horizontal infiltration approached to that of vertical infiltration-Wetted soil volume was related to total quantity of the irrigation water rather than emitter discharge rate.Based on the rules of wetted front movement,a proper emitter discharge rate was suggested for field practice.At the end of drip irrigation,water and salt had experienced important redistribution processes.The movement of water and salt to deeper soil layers promoted desalination of the upper soil layer.The effect was markedly better with low emitter discharge rates than high emitter discharge rates.The movement of salt was the most active onthe first three days of redistribution.A proper water volume per emitter that satisfies both the demand of a crop for growth and the need of the soil for salt leaching was worked out through the experiment,whichis sure of certain practical significance.

Abstract:The dynamics of soil organic carbon (SOC) plays an important role in the global C cycle,while decomposition rate of SOC is essential to understanding of soil C dynamics.The objective of this study was to explore how the natural ¹³C abundance method can be used to determine decomposition rates of organic carbon in whole soil and heavy faction of red soils using a laboratory incubation experiment.The soil samples used in the test were collected in March 2003 from a longterm field experiment at Yingtan State Key Agro-Ecological Experimental Stations in China and incubated aerobically at 30℃ in the dark for 180 days.Organic C contents and stable C isotope ratios of the whole soil and its heavy fraction were determined with an elemental analyzer and an isotope ratio mass spectrometer.Results show that the decomposition rates of native organic carbon in the whole soil ranged from 8.2×10^-4d^-1 to 22.0×10^-4d^-1,and in the heavy fraction from 4.0×10^-4d^-1 to 15.6×10^-4d^-1 for red soil incorporated with maize stalks.They were faster in soils incorporated with maize stalks than in soils without maize stalks,which suggests maize stalk incorporation may obviously stimulate the turnover of native organic carbon.Moreover,they were faster when the maize stalk application rate was 10% than when it was 5%,indicating that decomposition rate was related to amount of fresh organic carbon supplied by maize stalks incorporated into the soil.The findings will serve as a foundation for further studies to investigate turnover of SOC fractions using the natural ¹³C abundance method.

Abstract:Diurnal variation of soil respiration affected by fertilization at various growth stages of maize in black soil was in-vestigated with the static dark chamber method and gas chromatograph technique at the Hailun Agricultural Ecology Station.Results show that during the growth stages of maize,soil respiration rate displayed an obvious seasonal curve,with peaks occurring on the 23th,37th,50th,63th,87th and 110th days after seedling emergence,and the highest on the 87 th day,and a downward trend till the crop was harvested.Respiration rate of the rhizospheric soil followed a curve similar to that of the soil,while respiration rate of bulk soil was mainly affected by air temperature.The corn growing in the soil significantly affected soil respiration rate,which rose when the plant grew and decline when it got snile,showing a similar curve.Fertilization also significantly affected the respiration rates of soil and rhizospheric soil,but little of the bulk soil.Based on the entire growth period of maize,Treatment NPKOM was the highest in soil respiration rate and rhizospheric respiration rate,ranging in C 27.5～474 mg m^-2h^-1;Treatments NPK and NP were quite close,varying in the range of C 25.9～339 mg m^-2h^-1 and 29.5～358 mg m^-2h^-1,respectively;and Treatments NK and CK in the range of C 28.4～208 mg m^-2h^-1 and C 22.1～184 mg m^-2h^-1,respectively.In terms of the effect of fertilization,the treatments followed an order of NPKOM>NPK>NP>CK>NK.Through the whole growth period of maize,cumulative soil respiration peaked at the elongating-booting stage and milkyriping stage,following a doublet curve,whereas the cumulative respiration of bulk soil showed a peak at the elongating-booting stage,following a parabolic curve,and that of rhizospheric soil was the lowest at the seedling stage,peaked at the milkyriping stage,and decline afterwards.

Abstract:The study on protection of grounding grids from corrosion in soil is of great significance to safe operation of power networks Soil samples were collected from the grounding grid sites of 21 transformer substations in Cangzhou region as research objects Corrosive factors in the soil samples were determined and measured on the spots and in the lab,and the data were analyzed using the principal component analysis method for statistics Results show that chloride,total salinity and electrical resisti vity were the key corrosive factors in grounding grid soils Based on the indexes of chloride content and total salinity in the soil,the soil samples were sorted into three groups:coastal moderate/severely salinized soil,slightly salinized fluvo aquic soil and flu vo aquic soil When key corrosive factors and soil types were cited as evaluation indexes,corrosiveness of the soil samples was divided into three grades,that is,very strong,strong and moderate The Gangcheng Transformer Station and 3 others in the coastal region stand in soils,very strong in corrosiveness,the Liliubao station and 9 others in soils,strong in corrosiveness,and the Hancun station and 8 others in soils,moderate in corrosiveness.

Abstract:Thermodynamic characteristics of urease in four Shaanxi soils (Hapstagnic Anthrosds,Cal-Ustic Luvisols and Eum-Orthic Anthrosols) were systematically studied based on the relationship between kinetic parameters of soil urease and temperature,and classical enzymological theory.Results show that enzyme-catalyzed reaction could be divided into two steps,namely,formation of enzyme-substance complex (ES) and dissociation of the ES,of which the thermodynamic functions could thus be calculated,separately,and more information obtained of the mechanism of the enzyme-catalyzed reaction.The four soil samples differed significantly in temperature coefficient Q₁₀,activation energy Ea,enthalpy of activation ΔH,activation entropy ΔS and activation free energy ΔG,in the two steps.Q₁₀ of the soil urease ranged between 0.83 to 2.48,lower than the Q₁₀ in normal chemical reactions.The values of Ea,ΔH₁,ΔH₂ and ΔS of the soil urease in both steps were all positive except for in some individual treatments,suggesting more confusion and less ordering of the reaction,which means that more external energy is needed to complete the enzyme catalyzed reaction.The ΔG₁ in the step of ES formation and the ΔG and ΔH of the enzyme reaction were all negative,indicating that ES formation and the entire enzyme catalyzed reaction is a spontaneous,heatreleasing process.The ΔG₂ of ES dissociation was positive with no difference between samples,which means that type and fertility of the soils had minor influence on this reaction.It was also verified that the ES dissociation was a ratelimiting step of the reaction.This work provides a better understanding of the subtle differences in mechanisms of the enzyme-catalyzed reactions between different soils.

Abstract:Biochemical responses of earthworm (Eisenia fetida) to fluoranthene were studied and cited as biomarkers for monitoring PAHs-contamination of sublethal concentration in the soil.Earthworms were exposed to soils contaminated with different concentrations of fluoranthene (60,120,240,480,960μg kg^-1 and CK).After exposure for 1,3,7 and 14 days,earth-worms were collected for analysis of contents of total cytochrome P450 and MDA and the activities of glutathione-Stransferase(GST),superoxide dismutase (SOD),peroxidase (POD) and catalase (CAT) in the guts.Results indicate that within the range of concentrations in the test,fluoranthene triggered varying responses from biochemical enzymes in the guts of the earthworms,particularly from P450 in content,and from SOD and POD in activity but not as significantly from GST,CAT and MDA.The research also revealed that the effect of duration of the exposure was stronger than that of dosage limited within the range of sublethal concentrations on the biochemical responses.As biochemical sensitivity to the pollutant varies from enzyme to enzyme,it is necessary to use a combined multitime multi-index diagnostic method in diagnosing ecotoxicity of the pollutant in soil,with special stress on sensitivity and effectiveness of the indicators of exposure to the pollutant.

Abstract:A total of 74 soil samples were collected from three major types of soils,garden soil,paddy soil and natural soil in the Pearl River Delta,for quantitative analysis of residues of cischlordane (CC) and trans-chlordane (TC),and for enantiomeric ratios of those two chiral organochlorine pesticides.Results indicate that the concentrations of TC and CC were in the range of <0.01～13.70 and <0.01～15.70 ngg^-1,respectively,and appeared to be lognormally distributed.And of above 80 percent of the samples,concentrations were in the range of 0.1～1.0ng g^-1.The special high levels of chlordane in soils might be attributed to the use of the substance in the vicinity.Pesticide residues were not proportional to soil organic carbon content.

Abstract:A study was carried out with the upriver region of the Taihu Basin as a subject.Land use information about the area was acquired by means of TM/ETM image interpretation,and the upriver region was divided into small catchments with the aid of the IDRISI software.Field monitoring was performed in some selected catchments for analysis of relationships between the land use and river water quality in the catchments,and estimation of total concentration of the nonpoint source nitrogen in runoff from forest land and farmland.Based on the analysis and estimation,a cellbased model for simulating nonpoint source pollution is developed by combining the distributed hydrological model with measured values of the typical catchment.The model is well calibrated and validated with the monthly runoff data in the period from 1980 to 2000 and then used to simulate spatial distribution and flux of nonpoint source nitrogen to the Taihu Lake.Results show that the mean concentration of total nitrogen is 0.778 mg L^-1 in runoff from forest land,and 2.518 mg L^-1 from farm land.The modeled runoff volume and total nitrogen fluxes match well the observed ones,respectively,in the validation area.The average error value is 13% for the former,and 11.6% for the latter.The nonpoint source total nitrogen flux from the upriver region to Taihu Lake is 7 632 t a^-1,contributing about 40.8% to the total nitrogen flux of the entire basin.The flux varies with the type of land use.For farm land,the total nitrogen flux is 4 289 t a^-1,accounting for about 24.22% of the total nonpoint source nitrogen output,and for forest land and builtup land,the total nitrogen flux is 1 849 t a^-1 and 1 270 t a^-1,for about 24.22% and 16.64%,respectively.

Abstract:In order to evaluate nitrogen loss with runoff from paddy field and its affecting factors in the rice season,field experiments were carried out for three years in succession in the Taihu Lake region.When heavy rain shower brought water table of the flooded water 7 cm above the land overflow was piped to a runoff pooling pond.Results of the experiments show that dissolved N (DN) was the main form of N lost with runoff.Among the DN concentration of NH₄⁺-N was lower than that of NO₃^--N in general,and the former was correlated with N fertilization rate but the latter was not.Seasonal TN loads in runoff ranged between 1.0 and 17.9 kg hm^-2 during the rice seasons,accounting for 0.3%～5.8% of the applied N.N loss with runoff differed greatly between rice seasons and increased with the N rate in the same rice season.The relationship between TN loads in runoff and N concentrations in surface water before runoff could be expressed by equation y=ax+b.The risk of N losses through runoff in the rice season could be minimized by reducing fertilization rate,avoiding fertilization just before heavy rainfall and heightening the ridges of the paddy field.

Abstract:Relationship was explored of N loss through ammonia volatilization,runoff and soil leaching (at the depth of 1 m in the soil profile) with nitrogen (urea) application rate in red soil planted with Smooth Crabgrass (Digitaria ischaemum).Results show that N lost through ammonia volatilization in Treatments N 90,N 160 and N 230 (kg hm^-2) reached 0.67,1.24 and5.16 kg hm^-2,respectively,accounting for 0.74%,0.77% and 2.24% of the total N applied,showing a rising exponential relationship between the total amount of N lost through ammonia volatilization (y) and the N application rate (x) (y=0.156 3e 0.014 6 x).The amount of N lost through runoff was N 1.05,0.88 and 1.01 kg hm^-2,accounting for 1.17%,0.55% and 0.44% of the total N applied,respectively,in the three N treatments.There was no significant relationship between the total amount of N lost through runoff and the N application rate during the growth stage of Smooth Crabgrass.In this experiment,the amount of N lost through leaching was 2.05,2.86 and 4.09 kg hm^-2,which accounted for 0.91%,1.02% and 1.24% of N applied,respectively,showing an approximate linear relationship between the total amount of N lost through soil leaching (y) and the amount of N applied (x) (y=0.012 2 x+1.0877).

Abstract:It has been proved that there are two types of corn growing soils,balanced or unbalanced in soil nutrient supply. Therefore it is necessary to recommend proper nutrient ratios to achieve high yield of corn. A field experiment was carried out on calcareous drab soil,which is balanced in nutrient supply,in Shanxi to explore maximum fertilization rate and optimal fer tilization ratio forhigh yield of corn N and P application rates were set in two ways,with fixed N/P ratio or with N rate varying with P rate Results show that in the treatment with fixed N/P ratio,the maximum N application rate was 235 4 kg hm^-2,the highest corn yield 10 213 kg hm^-2,the optimum N application rate as 207 1 kg hm^-2,its corresponding yield 10 163 kg hm^-2,46 kg hm^-2,738 kg hm^-2,39 kg hm^-2 and 723 kg hm^-2 higher respectively than in the other,showing every additional kilogram of N could bring about an additional yield of 18 5 kg. The experiment demonstrated that N/P ratio of fertilization is the most important factor affecting maximum N rate and economic benefits. Through increasing N and P application rates while keeping them at a fixed rat io an optimal fertilization rate could be obtained.

Abstract:Tissue analysis of fluecured tobacco plants with different degrees of calcium deficiency sampled from the tobacco production base located in Southwest China show that the symptom of calcium deficiency on tobacco plants was mitigated with increasing Ca concentration in the leaves,but aggravated with increasing SO₄^2- and PO₄^3- concentrations in the leaves.Results of the hydroponic experiment indicated that high PO₄^3- concentration in the solution could induce symptom of calcium deficiency on tobacco plants.The greater the PO₄^3- concentration in the solution,the earlier the occurrence of the symptom,and the more serious the symptom.These findings revealed that serious calcium deficiency of tobacco plants in the production base resulted from application of the commercial organic manure containing high concentrations of SO₄^2- and PO₄^3-,which reduced solubility of Ca in the rhizosphere,thus hindering uptake and transport of Ca²⁺ by the plants.

Abstract:The midsubtropical low mountain and hilly region in middle Hunan is warm and humid in climate,covered with flourishing vegetation that has an abundant resource of soil animals in the soils underneath.A total of 36 018 animal samples were gathered from sampling sites during soil animal investigation in the hilly mountains of Middle-Hunan Province.They could be sorted into 31 groups,with Acarina,Collembola and Nematoda,being the dominant groups,which occupied 9233% of the total samples,and formed the main body of the forest soil animal community.The others were common groups and rare groups,accounting for 5.28% and 2.39%,separately.Soil animal intensity (10 ⁴ ind m ^-3) was affected by a number of factors,and vegetation and drywet alternation of soil are the main limiting factors.The findings at 4 sample sites showed the zonal evergreen broad-leaved forest and bushes-weeds were the highest in average density of soil animal,reaching up to 78.41 (10 ⁴ ind m ^-3) and 75.33 (10 ⁴ ind m ^-3),respectively,and the artificial coniferous forest the lowest,being only 56.41 (10 ⁴ ind m ^-3).The vertical distribution of soil animals in the soil was closely related with the surface accumulation of organic matter and the vertical variation of soil physiochemical characteristics.The results show the soil animals are mainly distributed in litter and humus layers,showing an obvious phenomenon of surface accumulation,and a downward decreasing trend.

Abstract:Out of 13 dominant species of plants growing in saline alkaline soil in Inner Mongolia,3 genera,26 species of AM fungi were isolated.Among them 3 species of Acaulospora,1 species of Archaeospora and 22 species of Glomus were identified,and Glomus geosporum and Glomus versiforme were the dominant ones in the region.All the 13 species of plants were susceptible to infection of AM fungi,and Zae mays and Iris lactea were the highest in AM fungal colonization rate,reaching 100%;AM fungal spore density of rhizosphere soil ranged from 29 to 182 ind g^-1 dry soil,and among the 13 species,Oryza sativa was the highest (182 ind g^-1 dry soil).Furthermore,AM fungal colonization rate of the dominant plants varied with soil types,showing an decreasing order of meadow solonchak>alkalized solonchak>salined meadow soil>alkalized meadow soil,but in terms of AM fungal spore density,alkalized meadow soil was the highest (101 ind g^-1 dry soil),followed by alkalized solonchak,meadow solonchak and salined meadow soil.No significant correlation was detected between AM fungal spore density and colonization rate

Abstract:To explore the resources of selenium enriching forest vegetables,an experiment was carried out of cultivating four species of wild forest vegetables,i e. Matteuccia struthiopteris Todaro,Aegopodium alpestre,Taraxacum mongolicum and Allium macrostemon in Dark Brown Forest Soil,using Na₂SeO₃ for fertilization,varying in application rate from Se 0.10 to 10.00mg kg_-1,directly into the top 15 cm soil layer Soil and plant samples were collected and Secontents were determined one year (a full growth cycle) after the application Results show that Typic Dark Brown Forest Soil displayed a high capacity of adsorbing and reserving around 90%~70% of the applied Se,from low to high application rate,in the top 15 cm soil layer of the total soil Se,about 6.03%~3.78% was water soluble Se and 19.36%~37.54% KH₂PO₄ extractable Se,they were all linearly re lated to the initial. Se application rate All the four species of wild vegetables tested were found capable of accumulating Se ex traordinarily from soils with strengthened soil selenium supply And the Se contents in these plants were 1.7~158.9 times as high as that in the plants in control (CK),varying with the application rate. The four species of plants were very different from each other in Se accumulation capacity and in variation pattern of Se accumulation with increasing Se application rate. On the whole,plant Se content was non linearly related to Se application rate,but when the application rate was low,a linear relation ship was found and varying in range from species to species It was also found that plant Se content was also significantly,posi tively but nonlinearly related to the contents of soil total Se,KH₂PO₄ extractable Se and water soluble Se,and linearly related when the application rate was low It is hence concluded that properly controlled soil Na₂SeO₃ application in Typic Dark Brown Forest Soil would be an effective way to cult ivate Se rich forest vegetables and to exploit Se rich vegetable resources under the quasi natural conditions of the forest region,except heavily perturbed coarse textured soil.

Abstract:A new concept of soil polarization was presented and defined as the non equilibrium or polarizing tendency of soil development that deviated from its original status of equilibrium due to long-term or continuous growth of the same single specie of trees,which was thought to be the fundamental obstacle to continuous growing of planted pure forest Based on this principle,both single and comprehensive index models were established,and criteria for gradation and a system for classification of soil polarization were also planned out In addition,these models were applied to a case study of planted pure forest of black locust (Robinia pseudoacacia L) in a gullied area,south in the Loess Plateau Results show that the soil therein falls in the po larization category of aridification plus sterilization.

Abstract:Food safety has aroused worldwide concern.In our country food safety is closely related to the issues of improving people's life quantity,safeguarding people's health,maintaining social stability,establishing a harmonious society,etc..It can be said in some degree that to safeguard food safety is to maintain ecological safety,economy safety,and national safety.Currently,the country is confronted with the following questions in the aspect of food safety:1) Insufficient food supply and low up-to-standard rate;2) High residue of poisonous and harmful materials in food and increased food poisoning accidents;3) Prominence of resource,ecology and environment problems,and latent threats to sustainable food production capability;and 4) Incomplete legislation for food safety,and inadequacy in law enforcement and management.Ecological agriculture is an important orientation for agricultural to develop in the current society,because of its significant functions of boosting production,increasing income,improving efficiency and protecting the environment,and its great contribution to improvement and optimization of agricultural ecoenvironment and production of healthy quality safe food.It can be said that ecological agriculture will play an important irreplaceable role in resolving a number of problems China is confronted with in the aspects of food supply,quality and safety,and sustainable development of food production.In order to guarantee safety food in the new century,China must make more efforts in developing ecological agriculture,adopting the following measures:To improve the awareness of ecological agriculture;to popularize ecoagricultural knowledge;to expand and apply ecoagricultural knowledge countrywide;to intensify scientific research on ecological agriculture and to attach more importance to industrialization of ecological agriculture.

Abstract:土壤持水曲线是研究土壤水动力学性质必不可少的重要参数。在已经建立的众多数学模型中,van Genuchten模型以其与实测数据拟合程度好而得到广泛的应用,而运用该模型的关键是如何获得其中的4个参数。

Abstract:新疆是我国最干旱、盐渍化土壤分布面积最广、土壤积盐最重的地区^[1]。这里特定的自然环境条件下发育着丰富的盐生植物,是中国盐生植物种类最多、分布最广的区域^[2]。1995年,Breckle将盐生植物分成三个类型:泌盐盐生植物、稀盐盐生植物(肉质化盐生植物)和拒盐盐生植物(假盐生植物)^[3]。这三种类型的盐生植物在干旱区盐生荒漠上均有广泛的分布。根际是土壤一植物生态系统物质交换的活跃界面^[4]。

Abstract:土壤酶主要源于土壤微生物代谢过程,以及土壤动物、植物根系分泌及残体分解^[1,2],土壤酶活性反映土壤生物活性和土壤生化反应强度^[3]。土壤酶活性与土壤物理特征(土壤水分、土壤温度、土壤空气、土壤团聚体)、有机质、pH、土壤微生物及土壤类型等关系密切[4]。环境因子如温度和湿度的变化、酸雨和臭氧等污染对土壤酶活性的影响也很大^[5,6],因而土壤酶活性也可作为监测环境变化和污染对土壤质量影响的生物活性指标。此外,由于土壤酶活性与土壤碳、氮循环密切相关^[7],因此土壤酶活性的研究常常还与全球气候变化相联系。目前土壤酶研究多集中在耕作土壤、草原土壤和森林土壤^[8~11]。

Abstract:花生是我国主要油料作物之一,是油脂加工业和副食品工业以及医疗等行业的重要原料,在国民经济中占有重要地位^[1~3]。近年来,我国花生的种植面积一般在400万hm2左右,居世界第一位^[1~3]。研究如何提高我国花生的产量和品质成为世界花生生产重要内容。日本20世纪90年代就有21%的花生直接用于食用,目前欧洲国家食用花生占80%,印度尼西亚食用花生达84%,我国也有食用花生的传统^[2,3,5]。花生成为国内外重要的保健食品^[2,4],食用花生的品质的研究越来越受到重视^[2,3]。花生是硼中度敏感作物,缺硼可导致花生空荚率高,特别是糖分含量降低^[5~7,9],从而影响花生的产量和食用品质。