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1.
Despite the widely acknowledged importance of arbuscular mycorrhizal fungi (AMF) in soil ecology, quantifying their biomass and presence in field soils is hindered by tedious techniques. Hence biochemical markers may be useful, among which glomalin-related soil protein (GRSP) could show a particular promise. Presently GRSP is operationally defined, its identification resting solely on the methods used to extract it from soil (citric acid buffer and autoclaving) and the assays (Bradford/enzyme-linked immunosorbent assay (ELISA) with a monoclonal antibody) utilized to detect it. The current assumption is that most non-heat stable soil proteins except glomalin are destroyed during the harsh extraction procedure. However, this critical assumption has not been tested. The purpose of this research was to challenge the GRSP extraction process to determine the accuracy of the Bradford method as a measure of glomalin; and to provide some assessment of the specificity of the ELISA monoclonal antibody. In two studies we spiked soil samples either with known quantities of a glycoprotein (BSA: bovine serum albumin) or with leaf litter from specific sources. After extraction 41-84% of the added BSA was detected with the Bradford method. This suggests that the currently used extraction procedure does not eliminate all non-glomalin proteins. Also, ELISA cross-reactivity against BSA was limited, ranging from 3% to 14%. Additions of leaf litter also significantly influenced GRSP extraction and quantification suggesting that plant-derived proteins, as would occur in the field, had a similar effect as BSA. Litter additions decreased the immunoreactive protein values, suggesting interference with antibody recognition. We conclude that the use of GRSP, especially Bradford-based detection, in the assessment of AMF-derived substances within field soils is problematic, it may be inappropriate in situations of significant organic matter additions.  相似文献   

2.
郇恒福 《土壤》2008,40(4):586-590
通过田间试验研究了施用油菜菜籽饼肥处理后,次生盐渍化温室土壤中的有效养分、水溶性盐分含量及盐分离子组成的变化,以评价施用饼肥改良次生盐浈化温室土壤的可行性以及在温室土壤上大量施用油菜籽饼肥可能出现的后果.结果表明:在次生盐浈化温室土壤上施用饼肥会显著增加0~20 cm土壤中的绝大多数有效养分特别是大量元素有效养分的含量和全盐含量.同时,施用饼肥也使得20~30 cm土壤中的部分养分和盐分离子含量显著增加,土壤次生盐渍化程度进一步加重.因此,施用饼肥并不能作为一种改良次生盐溃化温室土壤的有效措施,为避免土壤次生盐渍化程度的形成和发展,应减少设施农业中饼肥的施用量.  相似文献   

3.
Major changes to the extent and quality of farmland habitats, brought by the intensification of agricultural practice, are thought to be the main factors driving declines in a suite of farmland bird species in Europe. Recent changes in agricultural techniques have also contributed to widespread soil degradation, arising from increased soil exposure to erosion forces, declining soil organic content and increasing soil compaction. Although soils have a fundamental influence on ecosystem properties, the implications of soil degradation for farmland biodiversity have received little attention. In this study, we measure the influence of soil conditions on the distribution of a declining insectivorous farmland bird, the yellow wagtail Motacilla flava, relative to other habitat features in arable fields. Soil penetrability was found to have a significant influence on the abundance of territorial yellow wagtails at the field scale, together with crop type. Other measured habitat features had little effect on territory abundance, including soil organic content, crop height (within preferred crop types), field boundary habitats and availability of bare ground. Monitoring of invertebrate abundance across 20 cereal fields revealed a significant influence of both soil penetrability and soil organic content on aerial invertebrate capture rates. This relationship was strongest during the latter part of the breeding season, implying that settling yellow wagtails could use soil penetrability as a predictive indicator of prey abundance during the chick-rearing period. The strong relationship between yellow wagtails and soil penetrability suggests a potential causative link between soil degradation and population decline. The role of soils in determining abundance patterns and population declines of other farmland species may have been overlooked in previous studies.  相似文献   

4.
Influence of Al dissolution on soil ZPC (zero point of charge) measured by a potentio-metric titration (PT) method and a modified salt titration (STPT) method was examined using two strongly weathered soils from Thailand and two volcanic ash soils from Japan. The amount of dissolved Al ions increased with the increase in the concentration of a supporting electrolyte for the strongly weathered soils, while the increase was negligible for the volcanic ash soils.

ZPC value of the strongly weathered soils determined by the PT method was lower than that by the STPT method, due to the greater Al dissolution associated with the higher electrolyte concentration used in the PT method. Al ions adsorbed onto the soil surface would shift the ZPC to a higher pH value not as a result of the formation of hydroxy Al polymers, but due to the blocking of permanent negative charge sites, which could otherwise lower the ZPC. The σp value, as a measure of permanent charge or the amount of 11 or O11 adsorbed by a soil required to attain the ZPC, could be used to describe this phenomenon.

In the STPT method, the salt concentration was not high enough to causc a significant Al dissolution at the ZPC, which is considered to be a more suitable condition than in the PT method because the ZPC value can be evaluated at a low salt concentration as in the ease of field conditions for crop production. Thus, the STPT method is rccommendcd for the determination of the ZPC.  相似文献   

5.
Quantitative monitoring of Bacillus thuringiensis (Bt) insecticidal crystal proteins in soil has been hampered by the lack of efficient extraction/detection methods. A novel approach for simple and effective Bt protein extraction was explored by evaluating extraction solutions from invertebrate gut fluids. Marine worm gut fluids were identified as promising for extracting Bt protein from soil. An artificial gut fluid based on these marine worm gut fluids was developed using commercially available chemicals and was evaluated for its ability to extract Bt proteins from soil. On the basis of experiments with Cry1 proteins, the artificial gut fluid in combination with ELISA was highly effective for protein extraction and analysis in a variety of soil types and was well-correlated with bioassay results. Coupling of immunoassay with this extraction method provides, for the first time, an efficient, accurate, and quantitative assay for routine measurement of Bt protein residues in soil.  相似文献   

6.
黄河自河南孟津以下为地上河,沿两岸大堤外侧,形成宽约2-6公里,低于河床4-10米的背河洼地,是历来内涝和土壤盐溃化最为严重的地区,治理也很困难。近年来随着引黄灌溉事业的发展,不少地区种稻利用改良盐渍土,取得了很好的效果,但也有一些地区种稻以后,地下水矿化度虽只有0.5-1克/升,而土壤迅速返盐,稻田周围产生严重的土壤次生盐渍化。  相似文献   

7.
微咸水灌溉条件下含黏土夹层土壤的水盐运移规律   总被引:11,自引:3,他引:8  
黏土夹层影响着土壤水盐运移及分布,为了研究在含黏土夹层的土壤中进行微咸水灌溉时土壤的水盐运移规律,进行了春小麦微咸水灌溉大田试验,并在此基础上运用数值模型对土壤盐分累积趋势进行了模拟预测。结果表明,黏土夹层对土壤水盐运移具有显著的阻碍作用,黏土夹层以上土壤平均含水量、含盐量呈随灌溉水矿化度增大而增加的趋势,黏土夹层以下各处理土壤水盐分布几乎不受微咸水灌溉的影响;大定额冬溉洗盐后,各处理0~70 cm土层最大积盐率仍高达65.7%,部分盐分滞留在黏土夹层以上;土壤盐分分布预测结果表明,微咸水连续灌溉5 a后,灌溉水矿化度为4和5 g/L的处理土壤盐渍化倾向明显,不宜在含黏土夹层地区长期使用矿化度>3 g/L的微咸水进行灌溉,否则将对土壤环境产生严重危害。  相似文献   

8.
Abstract

Boron sensitive crops, kidney beans and soybeans, were grown in pots containing soil collected from a beet field and a nearby pasture. Two soil extraction procedures were used to measure boron concentrations in the soils. Dilute acid was used to extract what is believed to be readily available boron. A modified‐Soxhlet apparatus, which employed continuous leaching with hot water, measured what is believed to be slowly available boron. Plant boron status was determined by analyzing the above ground portion of the plants grown in two soils. The amount of boron in the plant tops provides an indication of biologically available boron or that boron actually available to plants. Although kidney beans and soybeans extracted more boron from the beet soil, both soil extraction procedures indicated that the concentration of boron was higher in the pasture soil. Neither extraction procedure proved reliable in predicting plant response.  相似文献   

9.
我国具有丰富的盐碱地资源,滨海盐碱地是其重要组成。运东滨海平原盐碱地具有地下水埋深浅,土壤盐分重,土壤水盐季节性变化强烈等特点。基于上述特点,该区域农作物限制因子为盐分胁迫、干旱和涝渍害。针对限制因子总结了各种农田生态工程手段的实施及原理。通过对当地常见作物3种胁迫的敏感时期分析,结合农田生态工程原理,在河北省南大港管理区的荒地进行了农田生态工程改良盐碱地实践研究。结果显示,棉花、玉米的产量可分别达到2.23~3.98 t·hm-2和4.6~6.7 t·hm-2,接近当地耕地的平均水平。小麦-玉米一年两熟粮食总产量可达9.6~10.8 t·hm-2,小麦-谷子一年两熟粮食总产量达到9.1~11.9 t·hm-2。农田生态工程显著地增加了作物的种植适宜性,使多种轮作制度成为可能。但是单项的生态工程技术都有一定的局限性,如咸水结冰灌溉会增加土壤盐分,暗管工程会降低土壤养分含量和有效性,因此农田生态工程应系统化和体系化。多种技术手段互补,最终实现调整盐碱地土壤水分、盐分季节性分配,使作物避开盐分、水分胁迫敏感期,使作物生长与土壤水盐季节变化耦合,完成作物生命周期并形成产量,最后在周年内达到土壤积盐与排盐平衡。暗管工程必将取代明沟作为盐碱地区排水的基础,也是各项生态工程的基础。而农田生态工程技术的多样化、系统化和体系化是未来改良盐碱地的发展趋势。  相似文献   

10.
Zilpaterol is a beta-adrenergic agonist approved for use as a growth promoter in cattle in South Africa and Mexico but not in the European Union, United States, or Asia. Here, we report the development of a monoclonal antibody-based enzyme-linked immunosorbent assay (ELISA) for zilpaterol. Mice immunized with zilpaterol-butyrate-keyhole limpet hemocyanin were utilized for monoclonal antibody generation whereas zilpaterol-butyrate-bovine serum albumin was used as a coating antigen for ELISA. Thirteen clones were isolated, and after the initial sensitivity and isotyping experiments, three clones were selected for further ELISA optimization. Studies indicated that the optimum pH was near 7.4. Clone 3H5 had the highest sensitivity to zilpaterol and some interaction with clenbuterol and terbutaline at high concentrations but not other N-alkyl [bamethane, (-)-isoproterenol, (+)-isoproterenol, metaproterenol, or salbutamol] or N-arylalkyl (fenoterol, isoxsuprine, ractopamine, or salmeterol) beta-agonists tested. However, clone 3H5 was not functional at high salt concentrations, which precluded further development for urine analysis. Clone 2E10 showed increased sensitivity as salt concentrations were increased and did not cross-react with any of the structural analogues tested. However, its sensitivity to salt and urine concentration changes could cause high variability. Clone 7A8 showed good sensitivity and only a modest change with the salt concentration changes. Clone 7A8 also demonstrated smaller changes in IC(50) and B(0) with increasing sheep urine or cattle urine concentrations as compared to clones 2E10 or 3H5 and, thus, was selected for further development. The IC(50) for all of the antibodies showed exponential increases with increasing organic solvents concentrations, making it desirable to minimize solvent levels. In conclusion, a sensitive, specific zilpaterol monoclonal antibody-based ELISA has been developed that can serve as a rapid screening assay.  相似文献   

11.
In Costa Rica, the Maquenque National Wildlife Refuge (MNWLR) contains a unique habitat gradient ranging from primary old growth forests, grasslands, pastures, to various ages of secondary forests. Within these primary old growth forests are extremely dense naturally occurring Bromelia pinguin (Bromeliaceae) patches that often grow with densities up to 2 plants per square meter. A previous study found that anti-fungal activity of this particular plant appears to be altering the fungal community in soils adjacent to these plants. No work has been previously conducted on the possible effects of this plant community on soil faunal communities and if seasonality contributes to changes in soil invertebrate populations along a moisture gradient. Thus, a study was conducted to assess the effects of this specialized plant community on soil invertebrates with respect to season, and if these changes in soil fauna guild structure could prove to be valid candidates as indicators of ecosystem condition with changes in precipitation. In addition, a meta-analysis was done to determine how the bromeliad-associated soil invertebrate communities differ from those in adjacent primary forest soils. Therefore, comparisons were determined from previous primary forest soil invertebrate environmental DNA (eDNA) to the current wet season bromeliad soil invertebrate eDNA. Roche 454 pyro-sequencing was conducted on the 650 bp fragment of the cytochrome oxidase subunit I (COI) gene of invertebrates to obtain and characterize soil invertebrate sequence composition. To determine relationships among soil fauna guilds across seasons, relative abundance of the sequences were calculated, and used in conjunction with EcoSim niche overlap and co-occurrence values. From the bromeliad seasonal soil fauna eDNA study, it appears certain invertebrate guilds are driven by moisture as indicated by fluctuations in relative abundance of each invertebrate guild across seasons in bromeliad patch soils, as well as indicated by EcoSim niche overlap values. In particular, Guilds 1, 4, and 5, should warrant further investigation as indicators of habitat condition. The meta-analysis showed that a naturally occurring modified environment (the bromeliad patches), can result in differences in relative abundance and partitioning of a limited resource between invertebrate guild structure. Those guilds associated with microbivorous and complex decomposition activities (i.e. Guilds 3 and 4), are more abundant in primary forest soils than bromeliad patch soils and could potentially used for bioindicators of habitat perturbations.  相似文献   

12.
干旱区典型盐碱土壤含盐量估算的最佳高光谱指数研究   总被引:3,自引:2,他引:1  
盐碱土的表层土壤含盐量是土壤盐碱化程度分级的主要因素之一。对西北干旱区不同含盐量和含水率的典型盐碱土进行了分析,运用统计方法分析了5种高光谱指数与土壤含盐量的定量关系,并通过对比研究,确定了能提高盐碱土壤含盐量估算精度的最佳光谱指数及定量预测模型。结果表明,不同的指数所选择出的对土壤含盐量最敏感的波段基本都位于近红外(NIR)和短波红外波段(SWIR),说明盐类矿物在近红外和短波红外波段(VNIR-SWIR)区域会产生特有的光谱特征。所选定的最佳光谱ND指数结构简单,易于计算,且对土壤中的水分不敏感,该技术对于大面积土壤含盐量制图具有较广的应用前景。  相似文献   

13.
辽宁设施栽培土壤盐分累积变化规律研究   总被引:13,自引:1,他引:13  
对辽宁省主要设施栽培地区土壤盐分累积变化规律的凋查研究结果表明:(1)设施栽培土壤盐分含量和电导率较露地土壤有明显增加,且变化幅度较大,是露地的2.0~6.0倍。沈阳、北宁两地设施土壤的盐分含量分别为1347.48mg/kg(CV=59.3%),1274.25mg/kg(CV=40.5%)。(2)设施土壤连续种植到4年左右为盐分累积的高峰期,此时土壤的平均含盐量为1861.28mg/kg,EC值为0.53mS/cm,已超过所种作物的生育障碍临界点(EC〉0.5mS/cm)。此后,盐分含量因设施使用率的降低及采取的相关措施而有一定程度的降低。(3)设施土壤各盐分离子的含量均较露地土壤大大增加,盐分的累积以NO3^-、SO4^2-和Ca^2+的相对富集为主要特征。(4)盐分在设施土壤中的运移同时存在着向下迁移和向表层聚集两种方式,且以表聚为主。各盐分离子的含量随土层深度的增加而降低,NO3^-、CI^-、Ca^2+、Na^+的累积迁移量较大,在0~100cm各土层内的含量都高于对应露地层次,其中,硝酸盐的大量累积和向下迁移势必对环境造成不利影响。  相似文献   

14.
设施土壤盐分的累积、迁移及离子组成变化特征   总被引:32,自引:1,他引:32  
通过对我国不同地区设施栽培现状的野外调查和取样分析,研究了设施栽培条件下土壤盐分的累积、迁移及离子组成变化特点。结果表明:1)设施栽培条件下,土壤含盐量的变化幅度大,且均明显高于露地土壤,各研究区域内已有40%8~9%的土壤含盐量超过了作物正常生长的临界浓度。2)设施栽培的可持续利用周期较短,连续种植到4年左右的设施土壤,其耕层盐分的累积量可达到作物的生长障碍临界点,之后因设施使用率的下降以及采取的措施而有所降低,但仍高于露地土壤。设施连续使用会导致土壤环境质量的不断恶化。3)设施土壤剖面(0100.cm)盐分含量均高于相邻露地,盐分含量随土层深度增加而降低,其中耕层(020.cm)的盐分含量显著高于其下各层;盐分离子在土壤剖面的运移同时存在着明显的向底层迁移和向表层聚集两种方式,但以表聚为主;此外,盐分离子的大量累积和向底层迁移,特别是NO3-的淋溶已严重影响到部分地区的地下水水质。4)设施栽培后,土壤中的NO3-、SO42-、Cl-、Ca2+、Mg2+、K+、Na+均有不同程度的累积,阴离子以NO3-和SO42-为主,阳离子以Ca2+为主。盐分的大量累积以及某些离子的相对富集在一定程度上引起了作物养分的供需失衡、土壤酸化、棚室内CO2供应不足等生产问题。  相似文献   

15.
We hypothesised that digital mapping of various forms of salt‐affected soils using high resolution satellite imagery, supported by field studies, would be an efficient method to classify and map salinity, sodicity or both at paddock level, particularly in areas where salt‐affected patches are small and the effort to map these by field‐based soil survey methods alone would be inordinately time consuming. To test this hypothesis, QuickBird satellite data (pan‐sharpened four band multispectral imagery) was used to map various forms of surface‐expressed salinity in an agricultural area of South Australia. Ground‐truthing was performed by collecting 160 soil samples over the study area of 159 km2. Unsupervised classification of the imagery covering the study area allowed differentiation of severity levels of salt‐affected soils, but these levels did not match those based on measured electrical conductivity (EC) and sodium adsorption ratio (SAR) of the soil samples, primarily because the expression of salinity was strongly influenced by paddock‐level variations in crop type, growth and prior land management. Segmentation of the whole image into 450 paddocks and unsupervised classification using a paddock‐by‐paddock approach resulted in a more accurate discrimination of salinity and sodicity levels that was correlated with EC and SAR. Image‐based classes discriminating severity levels of salt‐affected soils were significantly related with EC but not with SAR. Of the spectral bands, bands 2 (green, 520–600 nm) and 4 (near‐infrared, 760–900 nm) explained the majority of the variation (99 per cent) in the spectral values. Thus, paddock‐by‐paddock classification of QuickBird imagery has the potential to accurately delineate salinity at farm level, which will allow more informed decisions about sustainable agricultural management of soils. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

16.
The gradient of water vapor pressure between soil and air controls the rate of evaporation from soil, but it has not been possible to determine the humidity at the soil surface. We have devised an instrument to measure the surface humidity in the field. Thermocouple psychrometry is used to monitor air equilibrated with the soil surface in a chamber placed briefly on the soil. A programmable data logger scans the thermocouples and stores the data. We calibrated the instrument over saturated salt solutions, and over soils whose relative humidity was calculated from measured water potentials. The instrument worked well, but underestimated slightly at relative humidities above 90%. It can be used to distinguish between stage 1 and stage 2 evaporation for soils. In field trials, the surface psychrometer was used to monitor diurnal and day-to-day changes in soil surface humidity during the drying cycle after irrigation. The cumulative vapor pressure difference between the soil surface and the air at 1.5 m was highly correlated with soil evaporation from microlysimeters set between crop rows. Changes in the cumulative difference in vapor pressure were also closely related to the changes in the evaporation component of measured evapotranspiration, as estimated with a simulation model.  相似文献   

17.
检测多杀性巴氏杆菌毒素抗体的单抗竞争ELISA方法的建立   总被引:1,自引:1,他引:0  
本研究以纯化的多杀性巴氏杆菌毒素基因片段的原核表达产物作为抗原免疫小鼠制备单抗,并利用表达蛋白和多杀性巴氏杆菌毒素单抗酶结合物建立了竞争ELISA方法检测多杀性巴氏杆菌毒素抗体。经过研究确定抗原包被浓度为223ng/mL,待检血清最佳稀释度为1:2,酶标单抗工作浓度为1:3200,血清抑制率大于50%为阳性。应用单抗竞争ELISA和细胞毒性中和试验同时对82份血清进行猪多杀性巴氏杆菌毒素抗体检测,竞争ELISA的检出率为40.2%,细胞毒性中和试验检出率为36.6%,两者符合率达91.5%。试验结果表明,该ELISA方法特异性强,敏感性高,稳定性和重复性好,操作简便。本方法的建立在实验室诊断的标准化、猪群萎缩性鼻炎疫苗免疫效果的评价及流行病学调查方面具有应用价值。  相似文献   

18.
It is well known that lead (Pb) is strongly immobilized in soil by adsorption or precipitation. However, the reversibility of these reactions is poorly documented. In this study, the isotopically exchangeable Pb concentration in soils (E‐value) was measured using a stable isotope (208Pb). Soils were collected at three industrialized sites where historical Pb emissions have resulted in elevated Pb concentrations in the surrounding soil. Lead concentrations ranged from background values, in the control soils collected far from the emission source, to highly elevated concentrations (5460–14440 mg Pb kg?1). The control soil of each site was amended in the laboratory with Pb(NO3)2 to the same total Pb concentrations as the field‐contaminated soils. The %E values (E‐value relative to total Pb content) were greater than 84% in the laboratory‐amended soils, and ranged from 45% to 78% (mean 58%) in the field‐contaminated soils. The relatively large labile fractions of Pb in the field‐contaminated soils show that the majority of Pb is reversibly bound despite the fact that the binding strength is large. The Pb concentrations in soil solution were up to 3500‐fold larger for the laboratory‐amended soils than for field‐contaminated soils at corresponding total Pb concentrations. These differences cannot be explained by differences in labile fractions of Pb but are attributed to the decrease in soil solution pH upon addition of Pb2+‐salt.  相似文献   

19.
Slugs are a major pest in arable agriculture that are typically controlled by using pesticide-impregnated pellets (molluscicides). We received multiple requests from farmers in 2018 for research into the impact of slug pellets on earthworms because they had been told that ferric-based pellets were ‘worm-friendly’. We measured soil fauna feeding activities within Lumbricus terrestris middens on a replicated field plot experiment comparing the recommended product rates of a metaldehyde (4%) based or ferric phosphate EDDS (3%) based slug pellets. There was a significant decrease in feeding activity in the presence of either type of slug pellet, particularly in the top 25 mm of the soil indicating movement away from the pesticide. This could be explained by the significantly lower abundance (numbers and biomass) of earthworms in the topsoil. Four months after ferric phosphate-based slug pellet application, there was no significant difference between the control and treated plots in earthworm abundance, indicating the effects were temporary. In the laboratory, individual Lumbricus terrestris earthworms consumed up to 4 slug pellets over 14 days and no significant differences in biomass were measured. A burrowing fitness assay indicated that earthworms exposed to ferric phosphate-based slug pellets burrowed to a greater depth. This suggests an avoidance behaviour response, which could also explain the field results. A consultation with farmers (n = 68) rated this information service as useful and indicated widespread interest in minimizing the effects of pesticides on non-target soil fauna.  相似文献   

20.
通过室内模拟培养试验,研究了有机肥与尿素配施对设施土壤盐分的影响。结果表明:(1)设施土壤的含盐量和电导率均随着施肥后培养时间的延长,呈先升高后降低再升高的趋势,培养15~30d较高,30—60d降低,60d后又缓慢升高。设施土壤含盐量与有机肥施用量呈极显著正相关,而与尿素用量无明显的相关性;电导率则与尿素和有机肥施用量均有极显著正相关。(2)施用尿素不同程度增加了K+、Na+、Ca2+、Mg2+,NO3-的含量,施用有机肥显著增加了K+、Na+、Cl-的含量,设施和露地土壤盐分总量和离子组成差异不显著。另外研究了土壤盐分总量和电导率分别与K+、Na+、Ca2+、Mg2+、SO4^2-、Cl-等含量的相关性,均呈极显著正相关。  相似文献   

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