Abstract:The Sanhe small watershed was divided into many slope units with the aid of GIS and its nutrient loss was assessed on the basis of the results of the study slope nutrient loss by means of simulated rainfall, using the universal soil loss equation(USLE).Results showed that the total nutrient(organic matter, TN, TP, TK) loss could be well and truly estimated by calculating sediment in the small watershed, but in estimating of the available nutrients(available nitrogen, available phosphate, available potassium), the nutrients in runoff should not be neglected.In order to accurately estimate the nutrient loss in the small watershed, a runoff distribution model of the watershed should be established and used in combination with the soil erosion model with the aid of GIS.In the Sanhe small watershed, the average quantity of soil loss per year was 5 839t and for the average quantity of nutrient loss per year, the organic matter, TN, TP and TK reached 197.9, 7.42, 3.91, and 174.0 t, respectively.

Abstract:References between the Genetic Soil Classification of China (GSCC) and the Chinese Soil Taxonomy (CST) for GSCC-Luvisols were conducted and their quantitative and spatial distribut ion characteristics within CST were studied, based on 1:1M Soil Database of China, which consists of 3 parts, 1:1M digital soil map, soils profiles attribution database and soil reference system of China.GSCC Luvisols are typical zonal soils with a total area of 1 059 757.8km², including 7 GSCC Groups, such as Dark Brown Soils (36.0%), Brown Soils (23.8%), Yellow Brown Soils (20.8%), Brown Coniferous Forest Soils (10.0%), Bleached Baijing Soils (4.3%), Yellow Cinnamon Soils (5.1%) and Bleached Podzolic Soils (0.01%), as well as 25 GSCC Subgroups.It can be sorted into 4 CST Orders, Argosols (72.8%), Cambosols (26.1%), Primosols (1.0%) and Spodosols (0.1%), and further into 25 CST Groups and 47 CST Subgroups, making the reference so complicated that there is almost no one to one reference relationship.Analysis of the area ratios and standard deviations of a certain GSCC soil classified by CST showed that the lower the unit for reference, the easier the reference would be.It is clear that Typic Dark Brown Soils can be sorted to Typic Bori-Udic Cambosols only, Bleached Yellow Brown Soils to Typic Ferri Udic Argosols, Bleached Brown Coniferous Forest Soils and Superfically Gleyed Brown Coniferous Forest Soils to Histic Permi Gelic Cambosoils, Yellow Cinnamon Like Soils to Typic Hapli-Udic Cambosols, Typic Bleached Podzolic Soils to Gelic Hapli Orthic Spodosols and Gleyed Dark Brown Soils to Gleyic Hapli-Boric Argosols.In order to make CST more practical and easier to popularize, it is essential and urgent to keep on studying and developing the CST at lower unit level to establish basic soil classification units of CST.The result of the study is of high reference value to proper reference between GSCC and CST and application and development of CST.

Abstract:Anti-erodibility refers to soil s ability to resist the dispersion and suspension caused by runoff.The study on anti-erodibility in the Beichuanhe Basin of Datong County, a national experimental site for conversion from cropland into forest land and grassland, shows that all the 12 anti-erodibility indexes can be divided into 4 categories, i.e.inorganic clay, aggregate, inorganic colloid and water-stable aggregate, capable of reflecting 85.6% of the informat ion of the eigenvalues, by means of PCA.All the plant communities in the Beichuanhe Basin can be clustered into three kinds based on the fo categories with the Hierachical Cluster Method.The first kind with good anti-erodibility mainly includes native forests, and the second kind with medium anti-erodibility is composed of artificial forests on rehabilitated lands of the early days, whereas the third with poor anti-erodibility is made up of newly established artificial forests in rehabilitated lands.The anti-erodibility of artificial forests is getting stronger and stronger as the forest ages, approaching that of native forests.It is successful to reafforest steep croplands in a natural way, and such artificial forests can play a good role in soil and water conservat ion based on anti-erodibility and other related eco-functions.

Abstract:Based on field investigation of the land use, erosion distribution of an experimental forest catchment exposed to eight typical events of rainfall from 1996 to 1998 was modeled with the aid of the GIS and a number of models, which cover canopy interception, roughness of litters, SCS hydrology, sediment calculation and transferring rate of runoff plot.The results show that the event sediment of bare lands and water resource protection forest accounts for 92.47%~100% and 15.23%~7.53% of the total erosion sedimentation, respectively.Verification of the models based on the two typical events of 1997-07-31 and 1998-07-05 indicates the error of simulated runoff discharge and sediment were -3.24%, +10% and +32.3%, +39.34%, respectively.

Abstract:Experiments on infiltration from a surface point source were conducted in the laboratory.The results showed that the wetted solum appeared in the shape of a semielliptic cone and that remarkable power function relat ions were observed between horizontal and vertical wetting fronts and the infiltration time and a significant linear relationship the volume of wetted solum and the volume of water applied;When the volume of water applied was kept the same, the volume of wetted solum did not vary much with the dripping rate, which was kept in range of 2~4 L h^-1;in the process of point source infiltrat ion, the increment in soil water content had nothing to do with duration of the infiltration and the dripping rate, but appeared to a constant value being 0.326 for clay loam soil in this experiment.Based on the above-said findings, a model for empirical solution of characteristic values of wetted solum under surface drip irrigation was presented to predict horizontal and vertical wetting front and volume of wetted soil.

Abstract:Under erosion conditions, velocities and sediment concentrations in water flows running down five slopes different in gradient were measured.Results show that sediment concentration changes with velocity.The former is positively correlated to rill development.At the beginning of rill development, velocity of the flow increases gradually, and when rills come basically into shape, it decreases and then levels off.The velocity of the flow is the main factor causing production and transference of sediment.When the gradient of a slope is low, rills develop slowly and little sediment is produced.The production of sediment does not differ much when the slope varies between 10°~20°.When the gradient is at 25°, however, even less sediment is produced than 20°indicat ing a critical gradient existing between 20°and 25°.Based on the characteristics of a slope, analysis of the relationship between velocity of the flow and sediment concentration therein may help explain reasonably the critical gradient of the slope.When the gradient of a slope is bigger than the critical value, velocity of the flow increases at the beginning, bringing down sediment not less than that on the slope with gradient smaller than the critical value.In this case, a deep sink is more likely to form, thus reducing the velocity of the flow.Rills, however, complete their development within a short period of time, causing the velocity of the flow and sediment concentration therein to decline.As a result, the cumulated sediment eroded within a certain time from the slope with gradient bigger than the critical value is less.The measurement of velocity with the electrolyte pulse method explains some phenomena of the erosion process.If the spatio-temporal distribution of velocity is further measured, the study may likely go deep enough to reveal mechanism of erosion and provide more accurate parameters for establishment of a rational model for prediction of soil erosion.

Abstract:Compared with ion chromatography (IC), for inorganicion analysis capillary electrophoresis (CE) has its advantages, such as low consumption of reagent and time and low cost and its disadvantages, like low reproducibility and limited sensitivity.Analysis of soil aqueous extract for inorganic ions by CE is one of the fields that have been explored, however, so far the result of CE has not been matched to those of the popularly used methods, such as flow analysis (FA) of nitrate.This work focused on further study of parameters affecting the CE analysis of inorganic anions in soil, and comparison of its result with those of IC and FA.With the aid of the electrophoresis system using sodium chromate as the background electrolyte, cetyltrimethyl am monium bromide (CTAB) as the electroosmotic flow modifier and indirect ultraviolet detection method, length of soil extraction duration, effect of separation voltage and pH of the working buffer of capillary electrophoresis (CE) on quantification of inorganic anions were investigated.Using the chosen analytical condition, chloride, sulfate, nitrate and phosphate can be quantified in less than 5 min.Based on these results, chloride, sulfate and nitrate in soil water extract were analyzed by CE in five soil sam ples from different places in China, the results were consistent with that of IC.However, phosphate in the soil extract after extracting for 24 h without agitat ion was still under the limit of detection (LOD) of CE and IC, and the CE is relatively lower in precision compared with IC.A positive linear correlation of p< 0.10 was found between soil nitrate extracted with water, deter mined by CE and that extracted with 1 mol L KCl, determined with FA.

Abstract:Identification of new hyperaccumulators is of great importance to successful phytoremediation of the environment contaminated with heavy metal.A new manganese hyperaccumulator plant, Phytolacca acinosa Roxb., was found growing in Southern China through field surveys on Mn mine tailings dumps and greenhouse experiments.This species has not only remarkable tolerance to Mn, but also an extraordinary capacity for this element.With the maximum Mn concentration in the leaf reaching 19 300 mg kg^-1, the plant grew well on Xiangtan Mn tailings dump with Mn concentration being as high as 114 000 mg kg^-1.Under hydroponic conditions, the manganese concentration in the plant leaves could reach as high as 36 380 mg kg^-1 with the bioaccumulation coefficient of 55 at a Mn supply level of 12.000 mmol L^-1.P.acinosa could grow quite well hydroponically with Mn supplied at a level of 8.000 mmol L^-1, although its biomass was less than the plant's in control with Mn supplied at 0.005 mmol L^-1.With the Mn concentration in the media increasing, the manganese concentration in the shoots increased, but the bioaccumulation coefficient gradually decreased.The total Mn accumulated in the aerial parts of the plant rose first and then declined.At the Mn concentration in the solution reached 5.000 mmol L^-1, the Mn accumulation in the aerial parts of the plant was the highest (258.2 mg plant^-1).Partitioning of Mn between the aerial parts and the roots showed that 87%~95% of Mn was transported into the former in all the treatments of the experiment, demonstrating the great capacity of the plant transporting Mn from the roots to the aerial parts.P.acinosa therefore offers great potent ial for use in phytoremediation of Mn-contaminated soils and waters.

Abstract:Huainan with a 100-year coal mining history is an important coal production base of the country in East China, turning out 100 million tons of coal annually.A case study on heavy metals in soil contaminated by mining activity was conducted through the investigation of four soil sampling routes through 3 coal-mining areas different in mining history (about 100, 50 and 25 years, respectively).Soil samples were taken systematically from the lands nearby the gangue dumps.Heavy metals (Cu, Ni, Pb, Zn, Sn, Cr, Co) in the soils were analyzed by IRIS Intrepid Inductively coupled plasma-atomic emission spectrometry (ICP AES) in the Institute of Soil Science, CAS, and certified soil samples (GBW07403) from the China Geological Survey were used for analytical quality control.The results were validated with respect to accuracy and precision.The heavy metals in the soil nearby gangue dumps were mainly attributed to weathering and leaching of the coal-gangues.The results show that coal mining activities contribute greatly to heavy metal pollution of the soil and the metals accumulate.Moreover, the concentration of heavy metals decreases with the history of mining and weathering of the gangue, showing their high mobility, especially with.Co, Cu, Zn, Ni, and Pb.Their contents in some soil were higher above the first-grade criteria for soil pollution established by the SEPA.However, none of them surpass the second-grade criteria, indicating that the translocation of the heavy metals from the gangue damps to their surrounding soils is a slow process.

Abstract:Blue clayey paddy (BP) soil and red paddy soil (RP) were selected as a case study of differences in hyper-spectral and soil organic matter (SOM) spectral-parameter-models of paddy soils derived from different parent material.The results show that the reflectance of BP derived from the sediments is higher than that of RP derived from the Quaternary red earth within the studied bands as a whole, and the absorption characteristics of RP is more evident than that of BP within the absorption bands related to iron oxide.The variation of the first derivatives of reflectance of responsibility, on the whole, also tends to be more vigorous than that of BP, and it is more significant at the bands related to iron oxide and 2 200 nm especially.The number and wavelength of bands included in SOM content spectral-parameter-models differ drastically between BP and RP.The SOM content spectral-parameter-models of the paddy soils are shown to have unique characteristics related to the parent materials.

Abstract:Particulate organic matter (POM), as an active pool of soil organic carbon, play an important role in C sequestration in cultivated soil.Formation of POM is related to aggregate format ion and sensitive to land use and soil management.The objectives of this study are (1) to determine effects of fertilization on POM content in paddy soil;(2) to determine effect of fertilization on formation and stability of aggregates;and (3) to clarify relationship between POM and aggregate stability.Soil samples were collected from the experiment fields of the long-term fertilization experiment station treated separately with CK (without fertilization), NPK (chemical N, P, K fert ilizers), NPK(=) (double the dose in Treatment NPK) and NPK + OM (NPK plus farmyard organic manure).The results showed that fertilization increased significantly the content of POM in the soil.In Treatments NPK, NPK(=) and NPK+ OM, it increased by 1.1~1.3, 1.2~1.4 and 1.5~1.9 t imes over that in CK and in Treatment NPK+ OM it was 37%~71% higher than that in Treatments NPK and NPK(=).The C/N ratio decreased with the increase in aggregate size, suggesting that the POM in smaller aggregates was older than in larger ones.In terms of aggregate stability, the treatments were in a decreasing order of NPK+ OM> NPK(=) > NPK> CK.The aggregate stability had a very significant linear correlation with POM (r = 0.98, p < 0.01).These results suggest that fertilization increased POM level due to increased input of organic materials into soil, thus enhancing soil aggregation.

Abstract:Nitrogen stress compromises realization of yield potential in cereal crops more than any other single factor.For rice is the world s most important crop species, nitrogen adsorpt ion and utilization efficiency by rice is an important issue in agricultural production.Due to inhibited nitrification in the bulk soil of lowland rice field, researches on nitrogen nutrition of rice focus much more on ammonium (NH₄⁺) than on nitrate (NO₃^-).Much evidence has shown that rice can take up not only NH₄⁺-N but also NO₃^--N.The capacity varies with its genotype.The responses of rice to different forms of nitrogen and their physiological effects are poorly understood.The kinetics of NH₄⁺ and NO₃^- uptake by rice plants of different genetypes were studied in nutrient solutions containing either one or both N forms.The results showed that rice plants of both genotypes grew the best in the nutrient solution of mixed N forms though Indica rice had higher N uptake capacity than Japonica rice.Using solution containing a single form of N, the K_m of NO₃^- uptake was higher than that of NH₄⁺ uptake, indicating that the affinity for NH₄⁺ was greater than that for NO₃^-.The V_max of NH₄⁺ uptake was higher than that of NO₃^- in japonica rice while remained the same in Indica rice.When both NH₄⁺ and NO₃^- were present, the NO₃^- uptake was largely inhibited by NH₄⁺, the V_max of NO₃^- uptake in japonica and Iindica rice decreased by half and two-thirds, respectively.The NH₄⁺ uptake was slightly inhibited by NO₃^- in Indica rice while maintained in Japonica rice.

Abstract:Effects of rewetting of air-dried red soil on soil biota composition, nitrogen mineralization and nitrification were studied in the laboratory.Four treatments were designed: (1) rewetting of air-dried upland red soil (RU);(2) fresh upland red soil (FU);(3) rewetting of air-dried nursery red soil (RN);(4) fresh nursery red soil (FN).The results indicate: the populations of soil microorganisms including bacteria, fungi, actinomycetes in the rewetted red soil increased obviously after 5 days incubation when compared with those in the fresh red soil, especially the population of bacteria, which were 6.26 and 6.84 times as large as that in the fresh of upland and nursery soil, respectively.As a result of the increase in soil microbes, the soil microbial biomass C (SMBC) and soil microbial biomass N (SMBN) increased in the rewetted air-dried red soil treatments.The increasing population of soil microbes after 28 days.incubation leveled off and was still somewhat equal to or a bit smaller than that after 5 days's preincubation of all the treatments.However, the population of microbes in the rewetted air-dried red soil was still larger than that in the fresh red soil after 28 days.incubat ion.With the increase in microbe population and biomass, nitrogen mineralization was sped up, which led to increase in NH₄⁺-N concentration.After 28 days.incubation, the NH₄⁺-N concentrations in the rewetted ai-rdried soils increased in comparison with those after 5 days.preincubation and obviously higher than in the fresh soils.At the same time, NO₃^--N concentrations also increased, but they were significantly higher in the fresh soils than in the rewetted red soil.The experiment also shows that after 28 days.incubation, the population of freeliving nematodes in the treatments of rewett ing air-dried upland and nursery red soil of could hardly recover, being 16.0% and 30.1% of that in the fresh red soil, respectively.After 28 days.incubation of the rewetted air-dried red soil, the net mineralization and mineralization rate increased significantly (p < 0.05), but the net nitrification and the net nitrification rate decreased significantly (p < 0.05), when compared with that in the fresh red soil.The possible reason was that the populations of ammonium oxidi-zers and nitrite oxidizers, which play a key role in the process of nitrification, could hardly get recovered from the damage of air-drying.

Abstract:Effect of Bacillus megaterium P17 strain on solubilization of different phosphate rocks was evaluated.Through shaking flask experiment and SEM photos, optimum phosphate rocks for P-solubilizing bacillus P17 strain were screened out.Results showed that bacillus P17 strain could dissolve phosphate rock powders of different sources, especially those from Huangmailing and Huangjinkahuang mines of diagenetic metamorphism phosphorits.After 70 days of culture and 10 times of inoculation, about 81.02% and 78.97% of the total phosphorus in the Huangmailing and Huangjinkahuang phosphate rock powders was solubilized, respectively.Results of the experiment showed that P17 strain could improve the continuous exploitation rate of some phosphate rocks.In addition, after 7 days of culturing, 3.10 mmol L^-1 volatile organic acids and 40.5 mmol L^-1 and 51.1 mmol L^-1 non-volatile organic acids were detected in the medium with Huangmailing and Huangjinkahuang phosphate rock powders as its single phosphorus source, separately;Gas chromatography revealed that bacillus P17 could also generate organic acids, such as lactic, succinic, malic, citric and acetic acids, which can chelate metal ions, thus releasing P from phos-phate rocks.P-solubilization mechanism of bacteria P17 was discussed in this article.

Abstract:Total sulphur and available sulphur in the 305 samples of toplayer soils collected from thirteen main types of soil in Shaanxi Province were extracted by 0.01 mol L^-1 Ca(H₂PO₄)₂ and determined.Results indicated that the contents of total sulphur and available sulphur in these soils ranged from 33 to 769 mg kg^-1(av.360 mg kg^-1) and from 4.6 to 157 mg kg^-1(av.29.3 mg kg^-1), respectively.Heilutu soil (Cumulic Haplustolls, ST/1996) and Mianshatu soil (Udipsamment, ST/1996) had the lowest content of available sulphur among these soil types.The ranges of spatial correlation was determined through semivariance analysis of these data and were found to be 531 km for soil total sulphur, and 34 km for soil available sulphur, respectively.Spatial variability for soil total sulphur and available sulphur exhibited a gradual changing tendency, and spatial variation developed in large scale for total sulphur, and in small scale for available sulphur.Soil available sulphur in 13.9% of the total land in Shaanxi Province was lower than the critical value, 18.5 mg kg^-1, for soil sulphur deficiency, implying approx-imately 0.537 millions hm² of cultivated land could be sulphur-deficient in this province.In central Shaanxi Province, especially the west part of Yan'an city, the risk of soil sulphur deficiency is great.

Abstract:Bacillus megaterium A6(gusA) colonization in roots of rapeseed in rhizosphere microcosms was investigated by means of gene labeling technique and traditional technique.Rape seeds were inoculated with A6(gusA), an effective strain of bacteria in promoting growth of rape seedlings.Results indicated that A6(gusA) population decreased with the roots going down-wards and with the time after inoculation.Populations of A6(gusA) were not detectable on roots more than 8 cm apart from the hypocotyl base.The population density of A6(gusA) on roots reached the maximum of 87×10⁵cfug^-1 root 3 days after sowing, and then declined rapidly till 30 days when it leveled off at 22×10²cfug^-1 root in rhizosphere microcosms.The result showed A6(gusA) could increased dry weight of the plant and content of total N, total P and total K in the plant.

Abstract:Soil nutrient status, microflora and their biochemical act ivities and enzyme activity in the rhizospheric soil and non-rhizospheric soil under Rhododendron fortunei in 3 different types of forests were investigated.The results showed that the number of soil bacteria functional colonies were closely related to soil nutrients and soil enzyme activities.Under good sun-light and aeration, the rhizospheric effect was significant in the Guiyundong Rhododendron fortunei community (R/S value) as compared with that of the other two.However, because of high vegetation coverage and low soil porosity, the activities of catalase and peroxidase were low, the soil capacity of transforming toxin was weak and the process of humification was slow in rhizosphere of the Rhododendron fortunei communities in Huangjingdong and Yongziting.Besides the populations of fungi and actinomyces in the soil increased significantly.These are clear indicators of degradation of the soil properties.All the results indicate that degeneration of Rhododendron fortunei could be prevented by pruning canopies of the surroundings arboreal trees and cleaning out Indocalamus latifolius.

Abstract:Forest growth in relation to variation of soil properties variety in Chinese fir forest soils derived from granite with different preceding vegetation in Lishui region of Zhejiang Province.Research results show that no matter what kinds of preceding vegetation the Chinese fir forest had, such as masson pine, broad-leaved forest or shrub, the first rotation of Chinese fir grew faster than the second rotation of Chinese fir.And five years later, the difference in growth became very obvious.The soil under Chinese fir of a second rotation was the lowest in population of bacteria, fungi and azotobacters, but not in that of actinomycete.Compared with other soils different in preceding vegetation, it was lower in activities of invertase and urease.Its content of available P was significantly lower than the others, and so were its contents of calcium and magnesium.Stepwise regression analyses results show that tree growth was positively correlated with invertase activity, available N, available K, and Mg²⁺ contents and negatively with soil organic matter, urease activity, catalase activity in the Chinese fir forest soils different in preceding forest stand.

Abstract:The farmland resource management information system of Yongji City in Shanxi Province was established based on the Geographic Information System (GIS) technology.The system manages spatial database and attributive database with MapGis, and data input, application model analysis and statistics database with FoxPro, and overlays the current landuse map with the basic farmland protection map and the soil map, forming 6 782 patches, which are used as the basic management and evaluation cells of the spatial database, thus conforming land and soil type in every evaluation cell.The model of Analytical Hier archy Process (AHP) and fuzzy comprehensive appraisement were developed with Visual C++ language.Aimed at the actual conditions of Yongji City, it was decided through discussion among the expert group that 15 indexes were chosen out of 64 indexes for investigation of farmland productivity and evaluation of land quality.The 15 indexes were used to calculate the comprehensive evaluation index of each cell, which can be used as a basis for evaluation of farmland quality.The results of the evaluation show that the city is facing a series of problems, with its farmland, such as unreasonable fertilization structure, increasing acreage of low and moderate yield farmlands, neglected salt affected soil and Lutu soil.On such a basis, countermeasures were put forth with the aid of the system, it is easy for the city to gain full knowledge of productivity and quality of its farmlands and lay down a solid basis for building up soil fertility and soil amelioration.

Abstract:载体法是指利用适宜的高分子材料包埋或吸收肥料养分而形成的供肥体系,这是控制肥料养分释放的重要方法之一.利用高分子聚合物来阻滞肥料中养分释放的研究已开展得较多,并取得了较好的进展^[1];Henderson和Hensley^[2]利用淀粉接枝的聚丙酰胺盐及聚丙酰胺共聚物作为阻滞剂,土壤淋溶试验表明,铵态氮利用率由对照的25%提高到85%,但对硝态氮没有任何作用;Smith和Harrison^[3]利用聚烯烃类及淀粉类多聚物和肥料做室内培养试验,与对照相比,尽管大多数氮在一周内就释放出来,但多聚物能相对延迟养分的释放和扩散;Magalhaes等^[4]利用聚乙烯醇和丙烯酰胺共聚物作为氮的载体做淋洗试验,发现该聚合物对铵离子有很强的阻滞作用,但对硝态氮没有影响.

Abstract:非饱和土壤的水分运动对于污染物迁移有非常重要的影响.特别是对于一些建造于非饱和带中的放射性废物处置库中的放射性核素,由于其对环境潜在的巨大的危害性,一旦工程屏障失效,作为天然屏障,非饱和土壤将对核素迁移起决定作用,因此,研究非饱和土壤的水力学特征、特别是非饱和导水率的确定是核废物处置安全评价工作的重要内容.从土壤水分滞留曲线来计算非饱和导水率是实际土壤水动力学计算中常用的手段^[1].描述土壤水分滞留曲线有多种经验公式,其中van Genuchten方程由于其曲线形状与实测结果十分接近,近年来已被大量用于土壤水分运动的研究工作^[2~4].

Abstract:吸附行为是土壤中最常见、最重要的物理、化学现象之一.已有研究主要涉及土壤及不同组分对离子吸附容量的大小、吸附形态、吸附动力学等.由于测试手段的限制,关于被吸附态离子在土壤固相表面的形貌少有报道.随着表面测试技术及纳米技术的发展,原子力显微镜(AFM)被应用到土壤学领域.此技术是通过测量物体表面和挠性针尖之间的原子力来绘出表面图像.AFM是扫描隧道电镜(STM)的主要拓展,但与STM不同,AFM不仅能观测导体与非导体物质表面结构,还可研究物质表面微观的反应过程^[1,2].

Abstract:农药作为外来化合物,必然参与环境中物质循环和代谢,并影响环境的能量和物质循环.近年来,越来越多的新化合物进入农业环境,给农业生态系统带来了极大的压力,同时给人们提出了如何消除这种压力的问题.农药的迁移、吸附、代谢、富集等环境行为及其所产生的生态效应,尤其是有机污染物在环境中的降解问题备受关注.生物降解是环境中有机污染物分解的重要途径之一^[1],土壤微生物对外源污染物具有多种重要的代谢和转化作用,研究土壤微生物对农药在土壤中环境行为的影响,对预测其在环境中的变化趋势和防止农药对环境的污染有重要意义^[2].

Abstract:淡水资源的不足和大量耗竭将严重影响农业的可持续发展,因此,人们对消耗我国农业用水80%左右的传统水稻栽培提出了挑战^[1],水稻旱作也就越来越多地受到关注.其中,地膜覆盖旱作和利用半腐解秸秆替代地膜的覆盖旱作都受到了广泛的重视^[2~3].目前,旱作水稻的研究往往是以移栽后旱种的方式为主^[1~3],这不仅耗时费力,而且与水作相比,移栽旱作还存在活棵所需时间长、成活率低等问题.本试验采用旱直播地膜覆盖育苗技术,克服了上述缺陷,但在这种栽培方式下水稻对氮素的吸收利用情况尚不清楚.

Abstract:随着化学氮肥的大量施用,氮素的渗漏(淋溶)损失及其对地下水的影响以及由此造成的环境问题越来越受到重视^[1～3].但有关土壤动物活动,尤其是蚯蚓活动对氮素渗漏影响的研究少有报道.蚯蚓是陆地生态系统中最为重要的大型土壤动物,能影响土壤的形成发育,改变土壤的理化性质^[4～7],加速土壤养分的循环^[8～10],促进有机物的分解矿化^[11～13].蚯蚓的活动可能通过改变土壤物理性质、参与氮素的转化进而影响氮素的渗漏损失.

Abstract:作物生长所需的养分主要来源于土壤,因而土壤作为作物生长的营养库,其养分的变异必然会引起作物生长的变异.北方旱地土壤氮素形态一般以硝态氮为主,所以开展土壤NO₃^--N含量空间变异性研究对于科学合理地制定农田施肥方案,提高氮肥利用率,促进变量施肥技术的发展,实现精确施肥具有重要意义^[1～3].灌区田间实际情况表明,在土壤质地相同的区域内,土壤特性(物理、化学及生物性质)在同一时刻,各个空间位置上的量值并不相同^[4].喷灌是一种节水效果十分显著,适应性较强的灌水方式,相比传统灌溉其湿润层要浅,对硝态氮的淋洗以及对环境的影响必然也较传统灌溉不同.

Abstract:河流、湖泊的富营养化是当今水质管理面临的最大问题之一.地表水体的富营养化一般与养分年输入量增加有关^[1],因此控制地表径流和地下排水中养分(特别是磷)的输出被认为是降低富营养化风险最有效的途径^[2,3].以往的研究表明,地表径流中可溶性磷的浓度与土壤测试磷有关^[4～8],因过量施用肥料引起的高水平磷积累的土壤常是径流中磷的主要来源^[4].长期以来,土壤测试磷一直被用于评价土壤中植物有效磷的数量,并为确定获得预期的作物产量所需要的化肥用量提供依据.近年来,土壤磷的测试已被一些国家考虑作为保护水质识别哪些土壤应该禁止使用化肥和粪肥的依据^[9～11].