Abstract:Crop yield,N use efficiency,and environmental impact of a 14 year fertilization experiment with winter wheat and summer maize,carried out in fluvor aqutic soil in North China,were analyzed.The results show that Treatment NPK (150 kg hm^-2 chemical N fertilizer per crop plus a set rate of P and K fertilizer) has always been the highest in yield of either winter wheat or maize with the smallest annual variation.The average yield of winter wheat (over 14 years) and maize (over 13 years) was 5 261 kg hm^-2 and 7 633 kg hm^-2,respectively.Treatment 1/2OM (i.e.half of N from chemical fertilizer and the other half from organic manure) was slightly lower than Treatment NPK in average yield of the crops,but in Treatment OM (only or ganic manure applied at the same rates of N,P,K as those in Treatment NPK),the yields of winter wheat and maize on average were 22% and 16% lower than those in Treatment NPK,respectively,and varied significantly from year to year.The treatment showed a rising trend with the time in yield (p<0.05).The averaged N use efficiency was 60% for winter wheat and 61% for maize in Treatment NPK,51% and 56% in Treatment 1/2OM,and 34% and 43% in Treatment OM,respectively.Total N in the surface soil (0～20 cm) was increasing in all the above treatments,which were in the order of OM>1/2OM>NPK.The amount of N recovered by the plants plus N residue in surface soil (0～20 cm) accounted for 69%,75% and 69%,respectively in NPK,1/2OM,and OM.There was no evidence of downwards movement of NO₃^- to subsoil and the N₂O emission factors were less than 0.24% in all the three treatments.In contrast,NO₃^- content increased with the depth of soil profile to 100 cm in Treatment NK,of which the crop yields were not significantly different from those in CK (without fertilization) and the N use efficiency was almost equal to zero,but its N₂O emission factor was lower than those in Treatment NPK.These results indicate that in the investigated soil with winter wheat and maize crop in rotation,crop yields could be maintained at a high level by application of chemical N fertilizer at a rate of 150 kg hm^-2 and P and K fertilizers at a reasonable rate per crop season.In this case negative environmental impact was negligible.

Abstract:A study on distribution of soil available nutrients on the field scale is important for improving agricultural management,and for assessing effects of agriculture on environmental quality and degrees of the influence of some random factors,such as human disturbance of soil properties.However,soil nutrients are highly heterogeneous whether on a large scale or a small scale,and their heterogeneity results from many processes acting and interacting across a continuum of spatial and temporal scales.Due to nutrient loss along with serious soil erosion in hilly area of Three Gorges Reservior Area,some researchers have studied mechanism of soil nutrient loss and how to control soil nutrient loss,and others have explored variability of soil nutrients described with classical statistical methods.However,there is little information available on spatial variability and scales of soil nutrients in this area.Hence,spatial patterns of soil available microelements in tobacco soil were studied in Pengshui,using geo-statistics of ArcGIS.Results show available Cu,available Fe and available Mn took on normal distribution while the others were subjected to Asymmetric distribution;the coefficients of variation of soil available microelements ranged from available Mo of 29.47% to available Fe of 51.76%;global model and exponential model were applied to simulating them respectively;the random variance indexes of soil available microelements were all lower than their structural variance indexes and the available Fe and available Mn were characterized by relatively strong spatial correlation,while the others by weak one;available Cu,available Mn and available B tended to be lower,but available Mo,available Fe and available Zn were higher in content.

Abstract:Fluorite contents (including total fluorite,exchangeable fluorite,and water-soluble fluorite) in 400 paddy soil samples collected from the Hang-Jia-Hu Plain,Zhejiang Province,China,were determined and the guideline for evaluation offrelated environmental quality of the paddy soils in the region was studied.Results indicate that both the contents of total fluorite and exchangeable fluorite followed the normal distribution,and that of water soluble fluorite fit the logarithm normal distribution.The average content of total fluorite in the paddy soils developed from fluviatile deposit and marine deposit was 333.1mg kg^-1 and 324.3 mg kg^-1,respectively.The content of wate-rsoluble fluorite and exchangeable fluorite in the paddy soils developed from marine deposit was 1.55 mg kg^-1 and 4.03 mg kg^-1,respect ively.The content of total fluorite in the cultivated layer was higher than that in subcultivated-layer,regardless of soil types (Percogenic paddy soil,Hydrogric paddy soil,Gleyed paddy soil,and Submergic paddy soil),whereas it was the other way round with water-soluble fluorite.It is tentatively recommended that the guideline for evaluation of Frelated environmental quality of the paddy soils in the Hang-Jia-Hu Plain is 413.9 mg kg^-1 for total fluorite and 2.54 mg kg^-1 for water soluble fluorite.

Abstract:Chemical reaction in soil solution has some important effects on solute transport.Ion exchange and complexation reaction are the common chemical reactions observed in soil.An indoor leaching experiment was conducted to explore effects of the two reactions on solute transport.The traditional convection-dispersion equation (CDE) regardless of chemical reactions was simulated by CXTFIT,and a model coupled with ion exchange and complexation reaction was simulated by PHREEQC,a hydrologic geochemical software.Results show that the coupled model is more precise in simulation,which indicates that the coupled model is successful.

Abstract:A pot experiment was conducted to examine effects of earthworm (Pheretima sp.) casts on copper uptake by ryegrass (Lolium multiflorum).The experiment had three levels (200,400 and 600 Cu mg kg^-1) of Cu contamination of the soil (Orthic aquisol) prepared by adding CuSO₄#5H₂ O,two treatments of soil amendments,earthworm casts (15%) and back-ground soil (15%) and two treatments of plantation,with ryegrass and without ryegrass.Results show that earthworm casts significantly increased biomass of shoots and roots (p<0.001),and length,surface area,volume and number of tips of the root system,and the effect was the highest when Cu content of the soil was 200 mg kg^-1.It also increased copper concentration and accumulation in shoots (p<0.05),but decreased copper concentration in roots.That means earthworm casts can promote copper transportation from roots to shoots and copper accumulation in shoots.In addition,analysis of soil pH and Cu fractions (BCR sequential extraction) show that plantation of ryegrass decreased soil pH and increased content of exchangeable Cu,and these effects could be strengthened by addition of earthworm casts.It could be inferred that earthworm casts promote copper uptake of ryegrass mainly by stimulating growth and act ivity of the roots,which in turn affects the rhizosphere environment and enhances bioavailability of copper.

Abstract:Through pot experiment,effects of phytoremediation on microbial communities in soils different in nickel treatment level were studied.Two Ni hyperaccumulators and one Ni tolerant species were planted in paddy soils different in Ni concentration,ranging from Ni 100 to 1 600 mg kg^-1.After 110 days of incubation,soil microbial activities were analyzed.Results show that populations of bacteria,fungus,and actinomycetes and biomass of the microorganisms were stimulated when nickel was added at a rate of Ni 100 mg kg^-1 in nonrhizospheric soil.When the rate was over Ni 100 mg kg^-1 in the soil,adverse effects on the soils microbial communities were observed.Plantation of hyperaccumulators could increase both the population and biomass of soil microorganisms,because by absorbing nickel from the soil and excreting root exudates,the plants reduced nickel toxicity and improved the living environment of the microbial.However,different plant species had different effects on microorganisms in soil.Randomly Amplified Polymorphic DNA (RAPD) with 5 primers was used in this study in 25 soil samples of 4 types of soils.A total of 947 amplified bands were obtained,including 888 bands of polymorphic and 59 bands of nonpolymorphic.The results indicated that the composition of microbial DNA sequences had changed because of nickel addition in treated soils.Shannon-Weaver index of soil microbial DNA sequence reduced in nickel contaminated soils with increasing nickel concentration.The changes in Shannon Weaver index in the 4 types of soils ranged from 1.65 to 2.32 for A.corsicum,1.37 to 2.27 for A.murale,1.37 to 1.96 for B.juncra,and 1.19 to 1.85 for nonrhizospheric soil.With the same amount of nickel added to soils,the Shannon-Weaver index in rhizospheric soil with plant was higher than that in nonrhizospheric soil.

Abstract:Based on a 23year stationary field experiment on fertilization in red paddy soil,crop yield response to fertilization and its relationship with climate and soil fertility was probed.The experiment was designed to have six treatments,i.e.CK,N,NP,NK,NPK,and NKPM.Results show that changes in annual climate and its interaction caused significant variability of crop yield in all the six treatments,while the impact of changes in seasonal climate on crop yield varied between treatments,little in Treatments CK,NK and NPKM,but strong in Treatments N,NP and NPK.Soil fertility contributed stably to crop yield,at a rate ranging from 46.3% to 72.0%.With improvement of the fertilization recommendation,the six treatments fell into an increasing order of NPKMNPK>NK>NP>N in terms of crop response.Significant crop response to N fertilization lasted 17 years,and to Kfertilization 9 years,but no significant crop response to P fertilization was observed.Stability of the production decreased significantly in Treatments N,NP and NK.With the time going on the decline appeared in a linear curve and the three treatments were in the sequence of NP>N>NK in terms of decreasing rate.During the period from the 18th to 21years,their yields were close to or even lower than that Treatment CK.The production of rice,in both stability and yield,was raised significantly in Treatment NPK,where the crop response was more significant when organic manure was used to replace part of the N fertilizer.

Abstract:Humic substance (HS) can be divided into humic acid (HA),fulvic acid (FA) and humin (HM) according to solubility in alkali or acid solution.HM is a fraction tightly combined with soil minerals and hardly extracted.In recent years,researchers have conducted a series of research on HM and advanced some means of separating,fractionating and purifying the substance.Among them the Pallo method is quite complicated to operate,but capable of fractionating HM into ironlinked HM (HMi),claycombined HM (HMc),inherited HM(IH) and highly developed HM (DH).As the fraction of inherited HM is very limited in quantity,it was ruled into the fraction of highly developed HM,which was then called insoluble humin residues (HMr) in this paper.In the experiment,samples of cultivated black soil and meadow soil were collected from the Jilin Agricultural University Campus (N43°48',E125°23'),and samples of Aeolian sandy soil from the Yaojingzi Grassland Research Station (N44°45',E123°45'),Northeast Normal University,Jilin Province,China.The above samples were all taken from 0～20 cm topsoil layers,except the samples of black subsoil,which was collected from the soil layer,70～100 cm in depth in the tableland.The black subsoil (2 mm mesh) was mixed with powdered corn stalks (0.42 mm mesh) and some bacteria of normal soil bacterial groups.Then the mixture was put under incubation at 25℃ for 90 days.Results show that HMr is the dominant fraction of humin,accounting for 30%～60% of the total organic carbon(TOC) in quantity,and followed by HMi and HMc,accounting for 3.1%～5.5% and 1.5%～4.1%,respectively.The content of HMi is a little bit higher than that of HMc in all the soils,except in the incubated soil.The E₄/E₆ and ΔLogK of HMi is higher than that of HMc in all the soils.The IR of HMi is almost the same as that of HMc regardless of difference in soil,but the new-formed HMi in the incubated soil showed stronger aliphatic CH vibration (2 920 cm^-1).In terms of 2 920/1 620 ratio of both HMi and HMc,a decreasing order of incubated soil> Aeolian Sandy soil> black soil> meadow soil is found.From the above results,it can be concluded that HMi is simpler and more aliphatic than HMc in molecular structure,and HMi and HMc are simpler and more aliphatic in the incubated soil than in the normal soils.

Abstract:Accumulation of organic acids and their phytotoxicity in paddy rice fields incorporated with crop straws have been widely concerned.Laboratory incubation was conducted to investigate the accumulation of organic acids,including formic,acetic,propionic and butyric acid in soil solution under flooded conditions and the effects of C N ratios of straw materials and N application.Results showed that the concentration of organic acids in soil solution increased with the rate of straws incorporated.The overall accumulation of organic acids (especially propionic acid) was significantly higher in soil incorporated with wheat straws than with rice straws,while NH₄⁺ concentration in the soil solution was the other way round due to wider C N ratio in wheat straw.Addition of urea significantly reduced concentration of organic acids in soil solution and enhanced CH₄ flux but had no obvious influence on CO₂ flux in the wheat straw treatment,while in the rice straw treatment,the concentration of organic acids and CH₄ flux were less sensitive to N addition.Results obtained in this study indicated that wider C N ratio of wheat straw enhanced the immobilization of inorganic N and inhibited the transformation of organic acids to CH₄ whichled to higher accumulation of organic acids.N application can serve as one of the effective ways to reduce the accumulation of organic acids in rice fields incorporated with wheat straw,but may enhance CH₄ emission

Abstract:A potexperiment was conducted to study fate of ¹⁵N-labelled ammonium sulfate incorporated into soil under the rice-wheat rotation system for 5 seasons of cropping.Residue fertilizer N from previous crops would accumulate as the cropping and fertilization practices continued.Assuming that the cropping system and soil management did not change and the total soil nitrogen content remained constant,the replacement rates of soil nitrogen by fertilizer nitrogen could be calculated based on change in residualnitrogen in the soil.By fitting the data of residualnitrogen in the soil into different mathematic equations,a best fitting equation could be picked out in light of their correlation efficiency (R²).The equation could be used conveniently to figure out the replacement rate,which is really high,accounting for 20% within only 3～5 years.The calculated replacement rate,however,could not be extrapolated into field conditions anywhere and the calculation methods presented in this paper is only applicable to similar cases where the assumptions hold water to a certain extent.The significance of replacement rate was discussed

Abstract:A solution culture experiment was conducted to study effects of NH₄⁺-N/NO₃^--N ratio and phosphorus level on growth,and nitrogen uptake of spinach and activities of nitrate reductase (NRA),glutamine synthetase (GSA) therein.Results show that spinach plants in nutrient solutions,the same in phosphorus supply level,decreased in biomass with decreasing NH₄⁺-N/NO₃^--N ratio,but differed slightly between solutions of 25 75 and 0 100 in NH₄⁺-N/NO₃^--N ratio.In treatments the same in NH₄⁺-N/NO₃^--N ratio,spinach plants increased in biomass with rising phosphorus level in the nutrient solutions.Nitrate levels in spinach shoots increased with decreasing NH₄⁺-N/NO₃^--N ratio and phosphorus level,but did not vary much between treatments different in NH₄⁺-N/NO₃^--N ratio.Spinach nitrogen content increased with phosphorus level,but did not show much difference between treatments different in NH₄⁺-N/NO₃^--N ratio.Nitrogen accumulation in spinach markedly increased with decreasing NH₄⁺-N/NO₃^--N ratio and increasing phosphorus level,which were concurrent with the increase in spinach biomass.In solutions of mixed NH₄⁺-N and NO₃^--N,phosphorus deficiency significantly inhibited spinach uptake of NH₄⁺-N and NO₃^--N.When the NH₄⁺-N/NO₃^--N ratio was 25 100,the NH₄⁺-N amount absorbed by spinach growing in the solution deficient in phosphorus ac counted for 27.2% of the total nitrogen uptake,however,it dropped to 16.9% in the solution adequate in phosphorus.When the NH₄⁺-N/NO₃^--N ratio was kept at 50 50,the value was 45.4% and 23.9%,respectively.Apparently,the uptake of NH₄⁺-N was less depressed by phosphorus deficiency than the uptake of NO₃^--N.With increasing phosphorus level,NRA of spinach markedly increased in treatments the same in NH₄⁺-N/NO₃^--N ratio,but with higher NH₄⁺-N/NO₃^--N ratios,NRA of spinach was depressed,and it increased when the ratio was lower.Moreover,phosphorus deficiency depressed GSA seriously.At the same phosphorus level,GSA of spinach shoot increased pronouncedly with increasing NH₄⁺ N in nutrient solutions.There fore,it is feasible to decrease nitrate level of some leafy vegetables that are grown on those soils high in nitrate by applying more phosphorus fertilizer.

Abstract:During April to October 2004,a lysimeter experiment was conducted in Laizhou region to study the fluxes of water,salts and nutrients in a Soil-Plant-Atmosphere continuum (SPAC) under irrigation with saline aquaculture wastewater The experiment was designed to have five treatments:CK (plant without irrigation) and four treatments of irrigation with Leaching Fraction (LF) being 0.1,0.2,0.3 and 0.4,respectively Results show that in 4 treatments (LF=0.1,0.2,0.3 and 0.4),the irrigated water lost through evaporation from the soil and transpiration from the plants accounted for 36.5%,36.2%,37.0% and 37 3%,respectively,of the total evapotranspiration (ET_C) of Jerusalem artichoke throughout its growing season,the accumulation of saltreached 91.1,94.1,98.7 and 107.1 g,ammonium nitrogen 2.00,2.29,2.27 and 2.82 mg,nitrate nitrogen 1.81,1.40,1.29 and 0.92 mg and reactive phosphate 3.03,2168,2144 and 1167 mg,respectively in the root zone1 In conclusion,irrigation with saline aquaculture wastewater may play an important role in applying Jerusalem artichoke with water and nutrients unless positive measures are taken to control the negat ive impact of over accumulation of saltl.

Abstract:In order to test the hypothesis that arbuscular mycorrhizal fungi (AM fungi) can improve growth of vegetables cultivated in protected horticulture soils which was affected by secondary salinization as a result of over-fertilization,Lactuca sativa plants growing at three soil EC levels (607,1 236 and 1 866μS cm^-1) were inoculated with Glomus intraradices (BEG141) and Glomus mosseae (BEG167).Results show that with the increase in soil EC value,the lettuce decreased in biomass,but this decrement was greater in CK than in the inoculation treatment when soil EC was low,eg.607μScm^-1.Compared with the plants in CK,the inoculated plants had a higher NO₃^- concentration at the soil EC level of 607 and 1 236μScm^-1,higher P and chlorophyll concentrations at the same soil EC level.and a higher soluble sugar concentration in the root when soil EC was 607μScm^-1,but a lower when it was increased to 1 236 and 1 866μScm^-1.The findings suggest that AM fungi can improve the growth of lettuce plants at a lower soil salt (607μScm^-1) level,but reduced the growth at a higher level (1 866μScm^-1).Its possible mechanisms are to be discussed.

Abstract:Effects of petroleum contamination on counts,diversity and dominant populations of bacteria in paddy soils were investigated in the Shenfu Irrigation Zone,the largest zone irrigated with oilcontaining wastewater for more than 50 years in Northeast China.Bacterial genetic diversity was determined with 16S rDNA PCR-denaturing gradient gel electrophoresis(DGGE).Results show that total petroleum hydrocarbon (TPH) concentration in the paddy soil varied from 277 to 5 213 mg kg^-1 dry soil.Soil TPH concentration declined along with the distance of the irrigation channel from the water source,showing a gradient from upstream to downstream and was positively correlated with organic matter (r=0.691,p=0.057).At the current pollution level,the paddy soil TPH concentration was positively correlated with the CFU of aerobic heterotrophic bacteria (AHB) (r=0.928,p <0.001).While genetic diversity of the bacteria based on DGGE profiles was negatively correlated with TPH concentration (r=-0.715,p=0.013).Sequence analysis of prominent bands in DGGE profiles show that β and γ subgroups of Group Proteobacteria were dominant in paddy soil of the Shenfu Irrigation Zone,All or some of the populations may play a significant role in metabolizing the petroleum compounds.

Abstract:A chloroform-fumigation extraction—water bath method(CFEB) was developed for measuring microbial biomass C in waterlogged soils.Liquid chloroform was directly added to the waterlogged soil to be tested,which was fumigated for 24 h at 25℃ under normal atmospheric pressure and in darkness,and then were extracted with 0.5mol L^-1 K₂SO₄ solution.The extractions were carried out in 100℃ water bath for 45～60 min to remove chloroform residue before measuring TOC.Nonfumigation controls were extracted directly with 0.5 mol L^-1 K₂SO₄ solution.The method was tested on seven paddy soils which were incubated aerobically or anaerobically and compared with the standard chloroform fumigation extraction (CFE).The results of the tests were reliable and reproducible,suggesting that the CFEB is a rapid and effective method for measuring microbial biomass C in waterlogged soils.

Abstract:By measuring electrical conductivity (EC),the time it takes for ions to reach equilibrium in reaction in the soil-water system was investigated.The EC-time curves of 20 soil suspensions (30 g kg^-1) prepared out of 5 tested soils and 4 nitrate solutions of 10^-4/3z mol L^-1 showed that ECs of the suspensions all decreased until the ion reaction reached equilibrium after 100~300 hours.The curves of Wien effect of two yellow-brown soil suspensions (10 g kg^-1) that contained 10^-4mol L^-1 Cu(NO₃)₂ and Pb(NO₃)₂,respectively,varied with the equilibrium time in location and shape,and overlapped when the equilibrium time reached or exceed 480 hours.The EC value of suspensions (10 g kg^-1) of yellow-brown soil containing 2 10^-4mol L^-1 NaNO₃ and KNO₃ and the concentrations of Na⁺ and K⁺ions in their supernatants showed a similar tendency at first and reached equilibrium after 70 hours and 30 hours,respectively.These experimental results show that conductometry is indeed a simple means to determine time it takes for ions to reach equilibrium in reaction in the soil water system.

Abstract:An investigation of soil fauna was carried out in swamps,willowshrub meadows,cultivated lands and secondary forestlands in three different tundras in Da Xinganling Mountains in J une,August and October,2003.A total of 39 225 individuals of soil animals,belonging to 4 phyla,8 classes and 24 orders were collected and sorted into macro,meso/micro and hygric fauna.Analysis of the populations of the three groups of soil animals did not show any consistent positive relationship between them in community.The investigation of horizontal distribution of the animals indicated a decreasing trend of the numbers of individuals and groups of meso/micro soil fauna from island tundra to the continuous tundra,which is similar to the general law of the distribution of soil fauna (that is,the number of soil animals gradually decreased from low latitudes to high latitudes),and a reverse trend in terms of the numbers of individuals and groups and biomass of macrofauna and the population of hygrocole as well.Their inconsistent and even reversed distribution rules revealed complexity of the relationship between locality and region of ecosystem.The numbers of individuals and groups of soil fauna were significantly and positively related to contents of organic matter and total nitrogen in the soil.The investigation of vertical distribution of soil fauna indicated that the individuals and groups of meso/microfauna were mainly distributed in the surface soil layer,but those of macrofauna peaked in the sublayer.The analysis of soil fauna diversity indicated that the diversity index of meso/microfauna declined from the island tundra to the continuous tundra,whereas the diversity index of macrofauna did not show any obvious law of variation between tundras.

Abstract:Based on the validity classification of soil moisture in the Caijiachuan watershed,using the variogram as a main tool and the ordinary Kriging and indicator Kriging theory,the spatial distribution of soil moisture and validation was conducted through 291 sites soil moisture detection (different depth of soil profile,0~30 cm and 30~60 cm) by TRIME-TDR in research area.The used Kriging could acquire a fine estimation of soil moisture.The result shows that (1) the validation (valid and in-valid) of soil moisture was divided by 13.46% (0~30 cm) and 12.48% (30~60 cm),respectively;(2) The average of the soil moisture in the area is 10.94% (0~30 cm) and 11.88% (30~60 cm),respectively;(3) The area where the soil moisture is in the range of invalid takes about 75.7% (0~30 cm) and 55.7% (30~60 cm) of the whole reserch area,respectively;(4) The validity of soil moisture is in close relation with the slop directions;(5) The probability of soil moisture descends from northeast to southwest in research area;and (6) through the compare the ranger and probability of valid soil moisture in different depth (0~30 cm and 30~60 cm) of soil profile,the result shows that the latter is much more than that in former.

Abstract:An experiment was carried out to study changes in soil moisture in winter wheat field under the conditions of drip irrigation,furrow and ridge planting.Results show that drip irrigation had obvious effect on soil moisture content in the soil layer between 0 and 60 cm in depth.Because of soil evaporation and water absorption by plant roots,soil moisture content in the 0~30 cm soil layer changed the most drastically during the growing season,less in the 30~60 cm soil layer,and the least in the 90~120 cm soil layer.After irrigation,soil moisture in the 0~120 cm soil layer was distributed in a Z pattern.Drip irrigation showed greater effect on furrow planting than on ridge planting.Analysis of soil moisture content in every soil layer,demonstrated that the plant at the milking stage was the most water-consuming stage,and the tasselling stage came the next.Treatments without irrigation consumed the water in deeper soil layers.Soil moisture content in the ridge plant ing treatment was higher than in the furrow plant ing treatment.Compared with the flatten culture treatments,the furrow treatments increased the most in soil moisture content after irrigation,the ridge planting treatments came the next.One week after irrigation,soil moisture content dropped the most sharply in the flatten culture treatments,the next in the ridge planting treatments,and the least in the furrow planting treatments.As for soil water movement after irrigation,it was faster in the ridge planting and furrow planting treatments than in the flatten culture treatments.

Abstract:Soil microbial diversity is an important content of soil microbial ecology,which is a new frontal field in ecology.Soil microbial diversity encompasses functional,structural and molecular genetic diversities of microbial community,and is a key indicator of stability and functions of soil ecosystems.This paper reviews current development in researches of the field of microbial diversity in polluted soils at home and abroad based on the methods of isolating culture and biomarkers,and the knowledge of microbial diversity from the angles of different ecological levels,and explores advanced approaches,new ideas and issues in the research on soil microbial ecological processes aiming at new problems in soil pollution the world is faced with.

Abstract:土壤水分是土壤的最重要的组成部分之一,也是反映土地质量的一个重要指标。土壤中水分含量的高低对热量平衡、土壤温度、农业墒情均有重要意义。遥感技术具有快速、广域、现势性强等优点,所以用可见光、近红外、热红外以及微波等遥感手段探测土壤含水量的研究在国内外已得到广泛的重视和应用。目前,土壤水分遥感监测主要采用4类研究方法,即土壤水分光谱法、热红外方法(热惯量方法)、微波方法和植被指数法^[1~3]。

Abstract:质外体是指原生质体以外的所有空间,包括细胞壁、细胞间隙及分化成熟的木质部等。质外体是植物细胞吸收养分离子的必经之路,是养分物质的储存库和缓冲区,对调节细胞内外的物质运输、调节营养平衡有重要作用。张福锁等研究表明,不同基因型植物根质外体Fe的积累量不同,可以作为不同基因型植物Fe营养效率的生理指标^[1];另一方面,质外体pH值的变化还影响着质外体中离子的交换特性,较大程度地影响着许多跨膜转运的过程。NH₄⁺和NO₃^-均是植物可利用的重要氮源,植物吸收NH₄⁺和NO₃^-必然引起质外体pH值的变化,由此引起的质外体pH值的变化因植物种类和不同器官而不同。

Abstract:地球上的微生物,仅原核生物细胞总数就大约在4×10³⁰~6×10³⁰,包含的独立基因型在10⁶~10⁸种之间^[1]。因此,微生物所具备的分类、功能、遗传和系统发育等多样性在维持生物圈生态平衡和为人类提供资源方面起着重要的作用^[2]。然而长期以来由于受到研究方法和手段的限制,土壤中绝大多数微生物的功能还不清楚。环境样品的宏基因组学(metagenomics)是对环境样品中微生物群体基因组进行的分析,该方法在众多用于获得未培养微生物的生理和遗传特性的方法中,逐渐显示出强大的优势^[3,4]。

Abstract:关于根瘤菌与非豆科植物关系的研究近年来已取得了一定的进展。已有的研究表明,在自然条件下,根瘤菌能够在水稻及一些非豆科植物的根圈定殖及固氮^[1,2],具有植物根圈促生(PGPR)作用^[3~5],能促进植物根系有效地吸收土壤中的水分和养分,从而促进植物的生长发育,同时对植物体其他生命活动进行调控。还可以提高植物的抗逆性,减轻或抑制有害的根际微生物,从而间接促进植物生长^[6,7]。在禾本科与豆科植物混作体系中,接种根瘤菌后,两者的生物量和植株总氮量均有提高^[8~10],¹⁵N同位素示踪技术表明这是因为体系中的豆科植物向禾本科作物迁移氮素的原因^[11,12]。

Abstract:地处北亚热带向暖温带过渡季风区域的淮北地区,由于降水时空分布不均,土壤水分物理性质不良,造成旱涝频发,一直是该区农业生产的主要障碍因素^[1~4]。长期以来,如何合理调控水肥、提高施肥效率、培育土壤质量、实现高产稳产,一直是该区农业生产实践中面临的重要问题。本文对淮北地区主要旱粮作物小麦生育期间的水肥效应进行了系统研究,在此基础上对小麦生育期干旱缓解、灌溉与施肥效率提高的技术措施进行了初步阐释,为本区小麦高产稳产的水肥管理实践提供科学依据。

Abstract:青稞是大麦类作物中的一种,是西藏地区栽培面积最大、产量最多、分布最广的农作物品种^[1]。近年来,青稞的保健作用(富含-β葡聚糖和"生育三烯酚")已得到国内外公认^[1],因而青稞生产受到更广泛的关注。然而,根据西藏首次土壤资源调查结果,全自治区低磷(速效磷<10mgkg^-1)土壤占总耕地面积的46.9%~72.3%(内部资料)。土壤供磷不足是限制青稞高产的重要潜在因素之一,同时西藏目前没有一家化肥厂,生产、科研所需肥料全靠从内地长途运输。寻找一条经济有效的途径缓解西藏地区农业生产肥料紧缺的状况成为一项迫切的任务。

Abstract:大多数试验表明在缺P或低P土壤中接种AM真菌都能促进植物对P、锌(Zn)、铜(Cu)等养分的吸收和利用、提高产量、改善品质^[1~4]。而在高P含量土壤中除部分菌种外,大多数AM真菌侵染率较低、接种效果不明显^[5]。近年来,随着化肥工业的发展和进口量的增加,我国农田施(P)肥量越来越多^[6],大大抑制了AM真菌的发育及其功能。因此,筛选耐P肥菌株,评价高P含量土壤中不同AM真菌的侵染、发育和接种效应,获得适应高肥力土壤条件、并能增加作物养分吸收、提高产量的高效菌种,为大面积农田应用AM真菌提供依据和技术是摆在我们面前的一项紧迫任务。