Abstract:Being the most important determinants of soil quality,soil properties significantly influence land use and ecological processes.Study on spatial variability of soil properties is vital for sustainable land management.Samples of surface soils (0～20 cm) collected from 254 sampling sites all over Hengshan County,on the Loess Plateau were analyzed to study spatial variation of soil nutrients (include soil organic matter (SOM),total nitrogen (TN) and total phosphorus (TP) with land use types and topography.Finally,environment indicators.1 Significant differences were found between different land use types in soil nutrients,with the highest values in SOM and TN measured in soils from paddy field,and the highest value of TP in soils from terrace farm land.ields with slope gradients ranging in 0～3 were significantly higher than fields with higher slope gradient in SOM and TN.And little difference was found in soil nutrients between fields different in slope aspect,but a tendency was discovered that SOM and TN in fields on northern slopes was higher.Different correlations were found of soil nutrients with terrain attributes and remote sensing indices.The multivariate linear stepwise regression model was relatively precise for SOM and TN,but for TP,it was not so good.Such techniques may be applied as a first step in unmapped areas to guide soil sampling and model development.The regression-riging method can effectively reduce residuals in prediction by eliminating smoothing effect.So its predicted values are quite close to the measuresd,demonstrating that the regression-kriging method improves accuracy of prediction.

Abstract:With the aid of an electromagnetic induction gauge (EM38) and its mobile sensing system,spatial variability of soil salinity was analyzed in a field (200 hm²) typical of the Yellow River Delta for two critical seasons by using the univariate indicator Kriging procedure,and a soil salinity probability map at two different periods plotted based on the chosen criteria.Results indicate that apparent soil electrical conductivity is significantly correlated with salinity,and follows approximately the pattern of logarithmic normal distribution with some outliers in both seasons.Nested spherical models are fitted for indicator semivariance of the apparent soil electrical conductivity in both periods.Structural factors lead to isotropic spatial variability of soil salinity in autumn,while stochastic factors enhance anisotropy of soil salinity in spring,especially in the directions of north-south and eastwest.Soil salinity probability maps in different seasons show that the extent of soil salinization is generally high in the study area,and surface accumulation of soil salts during the drought season is the primary reason for this phenomenon.The joint application of the electromagnetic induction gauge and the indicator Kriging method provides a new approach to survey and quality evaluation of soil resources at different scales ranging from farms to regional levels,and reference in decision making for and management of agricultural water-soil resources.

Abstract:Distributions of soil saline ions and vegetation communities were studied in Phragmites communis land.Results indicate that spatial variation of soil saline ions was significant,with variation coefficient of the four types of cations (Na⁺、K⁺、Ca²⁺、Mg²⁺) ranging from 0.60 to 1.22,and of the four types of anion (HCO₃^-、CO₃^2-、Cl^-、SO₄^2-) from 0/35 to 1/41.Among the eight types of ions,Na⁺ was the highest in content among the four cations,and HCO₃^- among the four anions.Comparison between vegetation communities show that Puccinellia tenuiflora + Phragmites communis community was higher than Phragmites communis community in concentrations of the eight ions (p<0.05),and in soil EC,soil pH,plant height,and biomass as well (p<0.01).So with increasing soil electric conductivity and ion concentration,soil alkalinity increases,vegetation growth index decreases,and vegetation community turns from Phragmites communis community to Puccinellia tenuiflora + Phragmites communis community.

Abstract:Rational planning and utilization of land resources of the Three-Gorges Reservoir Region needs to be based on thorough investigation of the soil environment quality of the region.Field investigation using the multi-targeted geochemical method was carried out,test and mathematical statistics conducted of soil samples collected systematically from the surface layer over a large area,and standard comparison and Geoaccumulation index methods applied,to evaluate seriousness of heavy-metal contamination and environment quality of the soil in the Three-Gorges Reservoir Region.Results show that as a whole the region is quite good in soil environment quality,except for Wushan and Fengjie districts,where high Cr and Ni background values have led to existence of a certain area of Grade Ⅱ soils.Over 90% of the soils are in Grade Ⅰ in terms of As,Cu,Hg,Pb and Zn.Artificial pollution is local and limited in area.For instance,spots of Hg pollution are found only in the vicinity of residential settlements,factories and minings.In the case of Cd,the area of Grade Ⅱ soils is quite large,and they are mainly distributed along Wanzhou and Fuling.However,whether the extensive distribution of Cd Grade Ⅱ soils resulted from high natural background or human activities needs further study.The problem should deserve more attention.

Abstract:The study on spatio-temporal variation of soil heavy metals is of important significance in sustainable utilization of the soil and protection of the eco-environment.Soil samples were collected from vegetable fields (0~20 cm) in the preiurban areas of Hangzhou City,43 in 2001 and 74 in 2005,determined for total Pb and total Cu,and analyzed with the Morans Ⅰ,Geostatistics and the Fractal methods for their spatio-temporal variation of soil heavy metals Results show that themean content of soil Pb and Cu in creased form 38.73 mg kg^-1 and 31.20 mg kg^-1 in 2001 to 46.14 mg kg^-1 and 36.56 mg kg^-1 in 2005,respectively,demonstrating a significant increase The autocorrelated distance of soil Pb and Cu at the 0.05 significance level decreased from 3 500 m to 2 700 m and from 3 300 m to 2 800 m,respectively,showing a decreasing trend in spatial distribution of soil Pb and Cu from west to east across the study area.The accumulation of soil heavy metals might be attributed to intensified human activities.

Abstract:In order to explore potential of the variation of GSH and MDA levels in Eisenia fetida as bio-indicators in monitoring heavy metal contamination of soil,effect of copper on Eisenia fetida was studied using artificial soil and contaminated agricultural soil.Results show that the levels of GSE and MDA in E.fetida are significantly related to copper in the artificial soil,with correlation coefficients being 0.556,0.807 and 0.775 between Cu concentration and levels of GSH and 0.760,0.672 and 0.544 between Cu concentration and levels of MDA,respectively after exposure of the worms for 2,7 and 14 days.Both showed close dose-effect relationship.In natural soil,partial relationship was found between Cu content and levels of GSH and MDA in the worms with correlation coefficients being -0.830 (p< 0.001) and -0.599 (p< 0.05),respectively,and between Cd content and levels of GSH and MDA in the worms as well,with correlation coefficients being -0.697 (p< 0.05) and -0.690 (p< 0.05),respectively.Moreover,it was also found that GSH level in the worms was more sensitive than MDA level to soil heavy metals.

Abstract:Data from the expermient on arsenic adsorption by three variable charge soils show that As(Ⅲ) adsorption in creased with pH rising from 3 to 7,and the three soils followed the order: latosol > yellow soil > red soil.While,As(Ⅴ) adsorption decreased with rising pH in red soil and latoso,an opposite trend was observed in yellow soil,making the three soils in the order: yellow soil > latosol > red soil in As(Ⅴ) adsorption.These soils have greater adsorption capacity for As(Ⅴ) than for As(Ⅲ),and the adsorption of either As(Ⅴ) or As(Ⅲ) was related not only to content of the free iron oxides in the soils,but also to crystalline type of the oxides in the soils.The yellow soil showed larger adsorption capacity for As(Ⅴ) than latosol and red soil due to its high proportion of hyd rated iron oxides.Results from the binary system of As(Ⅲ) and As(Ⅴ) indicated that the two species of arsenic competed with each other for adsorption sites on variable charge soils; and As(Ⅴ) was more competitive than As (Ⅲ) under acidic condition,because the presence of As(Ⅴ) depressed the adsorption of As(Ⅲ) to a larger extent,and vice versa in red soil and latosol to a certain extent,but almost noeffect of the presence of As(Ⅲ) on As(Ⅴ) adsorption by yellow soilw as observed except with a high pH.

Abstract:Soil samples collected in paddy fields in Tianjin (TJ),Sichuan (SC),Jiangxi (JX) and Hunan (HN) provinces of China.The experiment was designed to have four levels of illumination,i.e.entire dark (D),light (L) and change from dark to light (D/L) and from light to dark (L/D) during anaerobic incubation of slurries prepared out of the paddy soil samples.Concentrations of Fe (Ⅱ) and chlorophylla (Chl a) were determined in the samples under incubation,to study effect of illumination on reduction of dissimilatory iron oxide.Results show that oxygen production of photosynthetic bacteria leads to oxidation of Fe (Ⅱ) in paddy slurry under anaerobic incubation.Light does not affect iron-reducing bacteria.Photosynthetic bacteria reproduce massively only in some paddy soils,and Chl a content increases first with illumination going on,and then levels off Anabaena sp.and Nostoc sp.of Cyanobacteria were identified respectively in TJ and SC soils,and both of these Cyanobacteria had the same Chl a absorption peak at 664nm,which suggests that oxygen production by photosynthesis Ⅱ occurred.A significant negative correlation was observed between Fe (Ⅱ) and Chl a content in the two calcareous paddy soils under anaerobic incubation.

Abstract:A study was carried out to explore composition and characters of humus in coastal paddy soil.Results show that the surface soil layer was the highest in organic carbon and N content regardless of humus fractions.In tightly bonded humus relatively stable in structure and humus acids,C/N ratio fluctuated less,while in loosely bonded humus and fulvic acids,it did in a wider range.The formers showed an accumulating trend in soils with the age of paddy planting,and the highest degree of aromatization and the most complicated structure in 1000-year old paddy soil.

Abstract:Effects of earthworms on soil mineral N were studied through lab incubation and long-term field experiment.It was found that earthworm greatly influence the NH₄⁺-N,NO₃^--N and NH₄⁺-N + NO₃^--N,and promoted the soil mineralization.In field experiment,NO₃^--N and NH₄⁺-N + NO₃^--N were significantly increased by earthworm in rice season of 2001 and in wheat season of 2003.However,there were no signification effects in other harvest season.In the labincubation experiment,the role of earthworm on soil mineralization was distinct.Especially in without cornresidues treatments,NO₃^--N,NH₄⁺-N + NO₃^--N,Cumulative N Mineralization and Net Mineralization Rate were all significantly increased by earthworm incubation.

Abstract:Balance of soil N,P and K is very important to the nutrient management and agricultural sustainability.It was monitored in a small-scale vegetable farming system in the peri-urban areas of Nanjing and Wuxi,China during July 2003-July 2004,and its affecting factors studied at the same time.Results indicated that in Nanjing organic manure was the main source of nutrient supply,while in Wuxi,chemical fertilizer and organic manure were both used,with the former being the dominant one.Balancing of soil nutrients revealed that soil N and P gained,more in Nanjing than in Wuxi in the case of the former,and more in Wuxi than in Nanjing in the case of the latter,while soil K was in positive balance in Nanjing and in weak positive balance or negative balance in Wuxi,where obvious soil K deficit began to appear.This kind of soil nutrient imbalance resulted from differences in type of fertilizers used,labor input and resultant farming management between the two systems.Therefore it is necessary to develop a rational fertilization technique in light of soil nutrient balance and it's affecting factors,so as to promote sustainable development of the agriculture in the periurban areas.

Abstract:An expermient using monolith lysmieter under a paddy field irrigation-drainage system was conducted to monitor and analyze soilnutrient balance in South Jiangsu Plain.Results showed that the paddy field ecosystem consumed 890~1 320 mm irrigation water in each season,and it might purify nutrients by absorbing 10.7~12.3,6.8~9.2 and -1.2~2.0 kg hm^-2 of NH₄⁺-N,NO₃^--N and TP (total phosphorus),respectively in all fertilization treamtent,regard less of application rate.Although nutrient leaching rate in creased with the fertilization rate,the net nutrient purifying rate did not seem to be closely related to it.Application of straw had a little effect on purifying rate,while application of pigmanure weakened the purifying function sign ificantly,and could even be deemed as a "source" of phosphorus in surrounding water bodies During the rice growing period,paddy field played the role of purifying the water of NH₄⁺-N and NO₃^--N and of TP as well,except for in the treamtent of adding pig manure NO₃^--N,however,was liable to leach in the early rice growing period.

Abstract:A two-year lysimeter experiment was carried out using simulated soil profiles of three major types of Anthrosols (Paddy soil) in the Dongting Lake area on effect of conventional chemical fertilizer (CF),controlled release nitrogen fertilizer (CRNF),and addition of pig manure (OM) on N,P and K leaching loss,to explore status quo and laws of nutrient leaching loss from paddy fields under the double rice cropping system in Dongtinghu Lake area.Results show total nitrogen (TN) leaching loss accounted for 2.28%,0.66% and 1.50%,respectively,of the fertilizer-N app lied in paddy field of Typic Hapli-Stagnic Anthrosols (THS),Endogleyic Hapli-Stagnic Anthrosols (EHS) and Typic Fe-accumuli-Stagnic Anthrosols (TFS) in Treatment CF.The significantly higher amount of leachate led to distinctly greater TN loss in THS than in TFS,even though TN concentration in the leachate from THS was close to that in TFS; both the amount of leachate and the TN concentration therein from EHS were significantly lower than that from the other two soils.Among the N lost through leaching,ammonium N (NH₄⁺-N),organic nitrogen and nitrate N (NO₃^--N) accounted for 39.7%,56.8% and 3.5%,respectively.Total potassium (TK) leaching loss from THS,EHS and TFS accounted for 14.0%,4.68% and 11.5% of the fertilizer-K applied,showing a decreasing order TFS > THS > ETS.The total phosphorus (TP) leaching losses from these soils were very limited,and not much different between treatments.Among all the treatments,TN concentrations in leachate in Treatment CRNF were the highest and significantly higher than that in CK in all the soils,and those in Treatments CF and OM were relatively lower than in Treatment CRNF,but significantly higher than that in CK only in THS and TFS.TK concentrations in leachate from Treatments OM and Treatment K (potassium chloride) were distinctly higher than that in CK in all the soils.Because nutrient leaching loss is a longterm and p rogressive process,this study has been conducted continuously for only 2 years,so the difference in N and K leaching losses between N and K fertilization treatments was not significant.

Abstract:A loe Nan Yan No.1 is a new cultivar of aloe cultured out of the cultivar of aloe barbadensis Mill after sequential hyd roponic cultivation in seawater and field cultivation under seawater stress.During the year from June 2003 to June 2004,afield experiment was conducted to make comparison in growth between Nan Yan No.1 and aloe barbadensis Mill irrigated with seawater in Yuedong,Hainan Province.Results show that 1) the two cultivars were more or less the same in yield when irrigated with freshwater,but Nan Yan No.1 was significantly higher than the other when irrigated with 30% and 60% seawater; 2) their responses to seawater stress varied between cultivars,i.e.Nan Yan No.1 cultivar did not change much in yield whether irrigated with 30% seawater or fresh water,but the other dropped significantly when fresh water was replaced with 30% seawater in irrigation; 3) irrigated with seawater the two cultivars were also significantly different in morphology or growth characteristics,e.g.Nan Yan No.1 was much taller than the other,but they were more or less the same in length,width and thickness of leaves; its root/shoot ratio increased with concentration of seawater in irrigation,while that of the other decreased a littlebit when it was irrigated with 30% seawater; when seawater concentration in irrigation was 30%,Nan Yan No.1 still showed orderly arrayed cells on the surface of leaves and distinct teats on the surface of cells,while the other began to lose its clear cell boundary and teats; when seawater concentration in irrigation was 60%; cell boundaries and stomatal structure were still quite clear with Nan Yan No.1,whereas only blurred cell boundary and damaged stomatal structure were found with the other; and 4) the two cultivar of aloe varied significantly in salt to lerant coefficient,and Nan Yan No.1 was awlays higher than the other when irrigated with seawater,regardless seawater concentration.

Abstract:Investigations were made of soil fauna community in relation to vegetation succession alongside roads in typical semiaridity grassland zone.It was found that when the original soil-vegetation system was completely destroyed,the soil macrofauna therein were extincted while soil meso-microfauna could be found surving in the new system because they depend less than soil macrofauna.Soil fauna increased obviously in diversity and density at the initial stage of vegetation restoration and varied from habitat to habitat at the climax stage.The difference of diversity indexes of soil fauna was not significant at the stage of vegetation climax and restoration.Coleop tera showed a trend similar to that other soil animals did in diversity index and they could be cited as indicators at different stages of vegetation restoration.The grey relevant coefficients of diversity of soil fauna community were high with soil pH value,total P,total K and soil natural moisture,suggesting that these soil factors are closely related to variation of soil fauna diversity.

Abstract:Uptake of aged and current residual p,p'-DDT and its metabo lites DDD,DDE,DDMU and DDMS (DDX for short) in soil by paddy rice (Oryza sativa) was researched with pot expermients in greenhouse.The total growth period of rice was 126 days.Resu lts reveal that recently applied DDT degraded much faster than aged DDT residues in paddy soil and its dominating metabolite formed was DDD.Subordinate metabolites DDMS and DDMU were identified by GC/MS.Paddyrice could absorb both forms,the aged and current DDX residues from soil,and tran sport them to aerial compartments; so that the bioavailability of lower leveled aged DDX shouldnt be underestimate.Despite a high concentration of DDD (900 ng g^-1) absorbed by paddy roots in soil treated with DDT recently,the tran smission of DDX from root to edible part of the plant was limited.Concentration of DDX in roots is not a good indicator of the status of DDX in brown rice.It was worthy noting that the root concentration factors (RCFs) for DDMS or DDMU were about 3 times as high as for DDD or DDE.The data illuminated more prominent bioava ilability of DDMS and DDMU than their maternal compounds.Regardless of the contents and forms of DDX residues in soil,similar contents of DDX were observed in brown rice from different treatments.Distribution of DDX changed obviously with DDX transporting to edible part from root.The reasons are: first,motilities of DDT and its metab olites from root to aerial are different,and second,farther degradation of DDX would occur in rice plant.

Abstract:An experiment was conducted in lab by inoculating cypermethrin-contaminated soil,separately,with cypermethrin,3-Phenoxybenzoic acid (3-PBA)-degrading bacteria CDT3 (Rhodoccus sp.) and PBM11 (Pesudomonas sp.) to study their effects on microbial remediation of the contaminated soil and soil microbial communities.Samples were collected from the inoculated soils and CK (uninoculated) on D0,D3,D7,D15,and D30 for analysis of residues of cypermethrin and 3-Phenoxybenzoic acid (3-PBA) in the soil as well as monitoring of dynamics of the microbial communities in the soil,using the plate counting method and denaturing gradientgel electrophoresis(DGGE) method.The analysis results show that the cooperation of CDT3 and PBM11 promoted the degradation of cypermethrin and its metabolite 3-PBA in the soil.As cypermethrin inhibits significantly native edaphon in soil,inoculation of these degrading-bacteria could eliminate the inhibitive effect of cypermethrin on edaphon,thus promoting restoration of indigenous microbial population and communities.But it could not be expected that the damage cypermethrin brings to the soil microbial structure could be removed within a short period of time.

Abstract:Degradation dynamics of carbendazim in soil and its effects on community diversity of soil m icroorganism s were investigated in a m icrocosm m im icking soil ecosystem.Half 2 life of carbendazim in soil was measured to be 8.6 and 6.8 datlevels of 2.0 mg kg^-1 and 4.0 mg kg^-1,respectively.Values of average well color development (AWCD) of soil microorganisms were significantly inhibited within the initial periods after treatments of carbendazim at levels of 2.0 mg kg^-1 and 4.0 mg kg^-1 soil.Meanwhile,significant reduction in the richness,evenness and superiority of soil microorganisms was also observed,which indicated that the inhibitory effect of carbendazim on soil microorganisms was increased with its concentration in soil.After the initial variation,soil microorganisms adapted gradually to carbendazim and recovered to levels similar to that in the control without carbendazim.

Abstract:The ability of rhizobia to symbiotically fix nitrogen from the atmosphere when forming nodules on their host plant roots requires signal transduction pathways LuxR/LuxI family proteins are a unique quorum-sensing system,found in many bacteria,LuxR is a regulatory prote in which regulates LuxI-type proteins in synthesizing autoinducer (AI) In this study,sequence analysis was conducted finding a LuxI type synthase gene,mrtI,and a regulatory gene mrtR present in Mtian shanense,which are homologic to the LuxR/LuxI type of protein.Using gene knock-out,mrtR was found regulating the expression of mrtI.Furthermore,and using lacZ transcriptional fusion,AHL molecule demonstrating a key role in mrtR expression,which proves that mrtR is autoregu lated.The root hair adherence experiment showed that mtR affected plant bacteria interaction.These data show that it is necessary to have MrtR bonded with AHLs for mrtI expression and the gene plays a key role in regulating the quorum sensing system of M.tianshanense.

Abstract:The aim of the present work is to study effect of flavonoid on pre-symbiotic growth of arbuscular mycorrhizal fungi cultured in vitro.Effects of flavonoid compounds (quercetin,naringin,rutin,umbelliferon,biochanin A,zeatin riboside,flavanon,apigenin,genistein and formononetin) on spore germ ination,hyphal growth and hyphal differenatiation of arbuscular mycorrhizal fungi Gigaspora margarita and Glomus geosporum were examined.Results show that quercetin and rutin stimulated spore germination and hyphal development of Gi.margarita,and quercetin,ranging between 0.5 μmol L^-1 and 8 μmol L^-1,significantly promoted hyphal growth,hyphal branching and formation of clusters of auxiliary cells,increasing hyphal length,number of hyphal branches and clusters of auxiliary cells by two or three times as compared with the control group,while the other types of flavonoids showed little effect on presymbiotic growth of Gi.margarita.Appropriate in concentration,formononetin,genistein and naringin,stimulated had positive effect on spore germination,hyphal growth and hyphal branching of Gl.geosporum,and apigenin,flavanon and naringin didformation of secondary spores.Biochanin Amerely had some stimulating effect on spore germination of Gl.Geosporum.Variation of the effect of flavonoids on development of arbuscular mycorrhizal spores depends on type and concentration of flavonoid compounds involved,and different flavonoids play different roles in promoting spore germination,hyphal growth and hyphal branching and formation of secondary spores at presymbiotic growth stage of the AM fungi.To study mechanism of flavonoids influencing presymbiotic development of AM fungi will help understand interactions between microbe and Plant.

Abstract:Rape (Brassica napus L.) is sensitive to boron deficiency and usually gets depressed in production when it becomes severe.Boron deficiency restrains reproductive growth more than vegetative growth of rape.Yellow-seeded rape (Brassica napus L.) is characterized by thinner seed coat and lower hullpercentage,which is correlated with higher oil,high prote in,and lower crude fiber contents as is compared with black seeded rape.Therefore,breeding of yellow seeded rape has become one of the main objectives in rapeseed production.To realize that target,it is important to explore physiological characteristics of yellow seeded rape in soils low in boron content at the flowering stage,and differences between yellow seeded and black seeded rapes.Two isogenic genotypes of rapes,yellow seeded and black seeded rapes (Brassica napus L.) were used in a field experiment for that purpose.Results show that in soils low in boron content,black seeded rape was more capable than yellow seeded rape of redistributing N,P and K in bottom leaves of the plants.Low soil boron content led to reduction of size and dry weight of floral organs,of either yellow seeded or b lack seeded rape,affected.the length s of p istil and stam en m ore of yellow seeded rape than of b lack seeded rape,and dulled the viability of pollens of both rape genotypes,but the effect was more obvious on yellow seeded rape than on black seeded rape.Besides,low soil boron content lowered the contents of soluble sugar,starch,free proline and soluble protein in the stamen and pistils of both rape genotypes,but the effect was more significant on yellow seeded rape than black seeded one.Compared to black seeded rape,yellow seeded rape was more sensitive to boron deficiency.

Abstract:土壤环境中的污染物积累及其在食物链中的迁移转化是影响食品安全的重大科学问题。重金属污染因滞留持久、高富集等特性,易于通过食物链进入农产品中,影响农产品质量安全,危害人类健康^[1,2]。因此,针对农田土壤中的重金属累积状况进行调查和评价,已是国内外广泛关注的问题。近年来,前人分别从不同的角度对土壤重金属空间分布特征进行了研究。

Abstract:土壤表面电荷特性是土壤十分重要的表面特性参数,其不但与土壤溶液中阴阳离子的吸附与解吸具有直接的关系,同时土壤中的离子扩散、土壤有机-无机复合体的形成以及土壤的水分性状在不同程度上也均受到土壤胶体表面电荷性质的影响。近年来国内外开始研究应用阳离子型表面活性剂对黏土矿物或土壤进行修饰,以增大对土壤中有机污染物的吸附能力^[1,2],由于采用表面活性剂能够使得土壤的表面疏水性增加而亲水性减弱,其表面电荷性质也必然发生相应的变化,而这种变化对土壤中有机、重金属污染物的吸附固定将会产生本质的影响^[3~7]。

Abstract:锰是一种常见的变价元素,其在土壤中的有效性主要依赖于土壤总锰量、pH、有机质含量、通气状况及微生物活性等,其中,最直接的是土壤通气状况和pH。自20世纪50年代以来,渍水土壤中锰的化学行为及移动性就引起了人们的关注^[1~7]。在自然状态下,锰以多种氧化物形式存在,Mn(Ⅲ)和Mn(Ⅳ)发生在氧化环境中,Mn2+主要存在于还原条件下,土壤体系中的氧化还原状况显著地影响着土壤锰的溶出和生物有效性。

Abstract:土壤侵蚀是当今世界最严重的生态环境问题,不仅严重制约着农业生产,而且也威胁着人类赖以生存的自然环境^[1,2]。黄土高原由于强烈的土壤侵蚀,土壤有机质流失量可达216 kg hm^-2a^-1,土壤全氮流失118 kg hm^-2a^-1,全磷流失255 kg hm^-2a^-1,土壤养分含量低已经成为限制该区农作物产量提高的主要因子^[3]。土壤有机碳来源于动、植物残体,经过一系列生物化学作用逐渐形成^[4]。在土壤中,有机碳主要存在于细小颗粒,而以小于2μm黏粒中有机碳含量较高^[5]。

Abstract:随着我国畜禽养殖业的发展,畜禽排泄物产量不断增加,从1980年的6.9亿t增加至2002年的41亿t,2002年的畜禽粪便产生量是工业有机污染物的4.1倍,成为农业氮磷面源污染的主要来源^[1,2]。农田土壤硝酸盐的淋失是我国地下水硝酸盐污染的一个重要原因^[3]。国内外在化肥氮素淋失方面开展了大量的研究。在施用有机肥的氮素淋失方面,国外主要利用试验和模型研究不同管理措施对养殖场、牧场和农田的氮素迁移的影响^[4~8],提出有机肥的区域管理措施和对策^[9~10]。

Abstract:烤烟是我国重要的经济作物,氮素营养对烟草的产量和质量起着重要的作用。烟碱含量是评价烟叶质量的关键指标之一,有许多因素影响烟叶中烟碱含量。比如降雨^[1]、外界温度、光照^[2~4]、土壤特性^[1]和栽培措施^[5~11]。在可控制因素中,氮素营养对调控烟碱含量显得尤为重要^[8,12~15]。肥料氮和土壤氮作为烤烟氮素的两种主要来源,其对烤烟氮素营养和烟碱合成影响如何?关于这方面的研究甚少。

Abstract:在对大田海水灌溉试验的基础上^[1,2],进行海水灌溉下的肥料试验。库拉索芦荟(Aloe vera)是一种CAM光合碳同化途径的多年生旱生经济植物,具有一定的耐盐性^[3,4]。在国外,芦荟研究的成果被广泛应用在医药、保健、食品等行业,已形成一大产业。最近的研究报告表明,与其他植物一样,盐分胁迫造成芦荟体内盐分积累、营养元素缺失,破坏了离子平衡,通过施用磷肥增加植株含磷量能够提高植物耐盐性^[5]。

Abstract:大量研究表明,盐碱土中存在着丰富的泡囊-丛枝(Vesicular Arbuscular;VA)菌根真菌^[1,2],但其丰富程度受多种因素的影响,如宿主植物种类、土壤因子和环境因子等等^[3]。近年来,国外一些学者初步探索了盐碱土中土壤因子与VA菌根真菌生长和发育间的关系^[4],其中以A liasgharzadeh等^[5]的研究较为系统,他们发现大不里士(伊朗西北部城市)盐碱土中VA菌根真菌孢子密度与土壤中砂粒的百分含量呈显著正相关,与Mg²⁺、Ca²⁺、Na⁺、Cl^-、土壤黏粒和速效磷含量呈显著负相关;VA菌根真菌侵染率与土壤中砂粒的百分含量呈显著正相关,与EC(电导率)、盐度及Mg²⁺、Ca²⁺、Na⁺、Cl^-、SO₄^2-和速效磷含量呈显著负相关。

Abstract:脂肪酶是用来催化酯类化合物的分解、合成和酯交换的酶,具有高度的化学选择性和立体异构性,可广泛应用于轻纺、皮革、化妆品、洗涤剂、医药以及食品等领域^[1]。随着研究的深入,脂肪酶还被应用于石油污染土壤的生物修复^[2]、柴油替代品的合成、旧报纸的脱墨、含油污水的处理^[3]等方面,可见脂肪酶在环保领域也具有良好的应用前景。由于微生物脂肪酶具有广泛的作用pH、作用温度范围和对底物的专一性,使其在酶学理论研究及实际应用中具有非常重要的意义。