共查询到20条相似文献，搜索用时 31 毫秒
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《Communications in Soil Science and Plant Analysis》2012,43(7-8):659-666
Abstract Kenaf (Hibiscus cannabinus var. Guatemala 4) was grown at Ayr in north Queensland under eleven nitrogen (N) treatments, including seven treatments with all nitrogen applied at planting and four split treatments in which half the nitrogen was applied at planting and half applied 67 days after planting. At weekly intervals from 36 days after planting, petioles from the youngest mature blades were sampled to investigate the possibility of using petiole sap analysis as a fertiliser‐management tool. The sap nitrate test showed promise in prognosing final stem dry‐matter yield. Relationships between final stem yield and sap NO3‐N at various sampling times, leading up to canopy closure of treatments supplied with 240 kg N/ha or more, are presented. Estimated desirable NO3‐N concentrations are also presented. Sap nitrate levels declined rapidly from 36 days after planting. The rate of decline of petiole nitrate levels depended upon the rate of nitrogen applied at planting. Monitoring sap nitrate over the four‐week period before canopy closure is expected and using the levels established as desirable in this work as a guide, will help the kenaf grower to identify the need for extra nitrogen. 相似文献
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“十四五”土壤生物学分支学科发展战略 总被引：3，自引：1，他引：2
土壤生物是地球生物多样性的重要组成部分。土壤生物驱动着土壤中有机质降解、元素循环、污染物转化与降解以及温室气体的产生与消耗,在全球粮食安全、环境保护以及应对气候变化等方面发挥着重要作用。土壤生物学是研究土壤生物多样性与分布、土壤生物的过程与功能以及土壤生物的调控与应用的科学。21世纪以来,分子生物学技术的突破与生态学理论的广泛应用极大地推进了土壤生物学研究的发展。本文回顾了土壤生物学科的发展历程,详细介绍了土壤生物学科的发展现状,提出了土壤生物学科在理论与应用上的发展趋势,并对未来土壤生物学科的发展方向进行了展望。随着多学科交叉融合以及研究手段的进步,土壤生物学迎来了一个新的发展时期。土壤生物学研究在生物资源挖掘、时空分布格局、生态服务功能和生物调控等方面取得的重要成果,将更好地服务于土壤健康、植物健康、人类健康以及我们的星球健康。 相似文献
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Zeraoui Ahmed Benzerzour Mahfoud Maherzi Walid Mansi Raid Abriak Nor-Edine 《Journal of Soils and Sediments》2020,20(6):2709-2716
Journal of Soils and Sediments - The objective of our work was to develop a software for the optimization of the processes of treatment and formulation of dredged sediments for utilization in civil... 相似文献
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根系调查取样点数确定方法的研究 总被引：10，自引：0，他引：10
根系是植物与外界环境进行物质和能量交换的场所，其分布特征反映了植物对环境的利用程度，随着科学的发展和技术的进步，人们对根系的研究也逐渐从定性走向定量，科学的根系调查方法是进行根系定量研究的关键。在已有的根系调查资料的基础上，应用数量统计的方法，对应用土钻法进行根系调查取样所需要的样点数进行了计算和分析，结果表明，应该按照不同立地，不同取样范围进行根系调查，根据调查的需要和实际状况，确定不同取样范围内所需要的取样点数，并对1／4样圆法的进行了改政和修订，提出了一种新的野外取样的方法。 相似文献
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R.J. Fuller 《Biological conservation》1980,17(3):229-239
A method is described which was used to classify the ornithological interest of more than 3,000 sites in Britain according to their importance for conservation. Although extremely wide, the range of ornithological interest could be described by three site attributes: population size, diversity and rarity. For any site, quantitative criteria enabled each attribute to be assessed separately in terms of five levels of conservation importance: international, national, regional, county and local. Each site was assigned to the highest level of importance derived from the application of the criteria to the ornithological data. This standardised classification identifies priority sites for conservation planning purposes and it is suggested that it could form a basis for techniques of making detailed comparisons of site quality. 相似文献
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中国土壤环境质量标准中重金属指标的筛选研究 总被引：13，自引：0，他引：13
我国土壤重金属污染问题十分严重,但目前国家的土壤环境质量标准已不适应当前土壤环境管理的需求,在指标体系上主要体现在重金属污染物项目过少,对一些新出现的污染问题无法有效监管。本研究通过深入调研美国、加拿大、荷兰、德国、澳大利亚、日本、中国台湾和香港等发达国家和地区的土壤环境标准,并将他们的重金属指标与我国现行的土壤环境质量标准中的重金属指标进行系统比较分析,提出我国土壤环境质量标准中重金属指标的修订建议。主要是要补充六价铬、有机汞等高毒害重金属价态和形态的标准;新增铍、锑、铊、钒等新型重金属污染物的土壤环境质量标准;同时,结合石灰(岩)土高背景区土壤,探索建立基于有效性的土壤重金属浸提态标准体系;为实现我国土壤重金属污染的风险管理提供科学依据。 相似文献
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The realization of the benefits of stubble catch crops (CC) cultivated after the harvest of the main crop requires the ability to produce substantial amounts of biomass before the onset of winter. The growth and biomass production of CC is primarily determined by the time period of sowing and weather conditions of the site. The construction of a new indicator of agroclimatic conditions for the cultivation of CC is described. This indicator includes the possible time period for CC sowing according to the harvest time of the preceding main crop, temperature, and water conditions for emergence and growth. The termination of growth due to low temperatures is considered. The assumptions used for the construction of the indicator, and the relationships to CC biomass were validated with data from field experiments. The resulting maps of regions in the Czech Republic with similar indicator values for three groups of CC differing in temperature demands are shown. 相似文献
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The gas chromatographic method for determining total cholesterol in multicomponent foods, collaboratively studied by the AOAC in 1974 (Method 1), has been evaluated by 9 collaborating laboratories and compared with the Interim Methodology Instructions No. 2 modified method (Method 2). The 5 samples selected for collaboration were deviled ham sandwich spread, vegetable beef stew, frozen chicken pot pie, frozen fish sticks, and mayonnaise. The recovery data were obtained from a sample of wheat germ oil spiked with 0.297% cholesterol as cholesteryl palmitate. Collaborators performed 2 replicate analyses on all samples by both methods. The statistical evaluation of the results showed that Method 1 is superior to Method 2. Average recoveries from the spiked wheat germ oil samples were 91.4% (9 laboratories) and 85.8% (7 laboratories) with coefficients of variation of 12.5 and 14.4%, respectively. Based on the collaborative results and statistical evaluation, Method 1 has been adopted as official first action. 相似文献
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Ferenc Szurdoki András Székács Hong M Le Bruce D Hammock 《Journal of agricultural and food chemistry》2002,50(1):29-40
Sensitive and selective enzyme-linked immunosorbent assays (ELISAs) in the immobilized antigen format were developed for fenoxycarb (1), an insect growth regulator (IGR). The parent molecule [ethyl 2-(4-phenoxyphenoxy)ethylcarbamate] was derivatized at several positions to obtain haptens (2-5) that were used to produce protein conjugates and rabbit polyclonal antisera. Amino derivatives of fenoxycarb at the terminal and internal rings (2 and 3, respectively) were linked to carrier proteins by azo coupling. Carboxyalkyl-spacer groups were attached to the ethyl group and the nitrogen atom of the target compound (1) to obtain haptens 4 and 5, respectively. Hapten-homologous ELISAs based on protein conjugates of compounds 2 and 4 determined fenoxycarb in the mid-ppb range (IC(50), 102 and 95 ppb, respectively). A more sensitive hapten-heterologous ELISA (IC(50), 17 ppb; detection limit 0.5 ppb) involved the antiserum raised against a conjugate of hapten 2 and the plate-coating antigen obtained from compound 3. These assays displayed no significant interferences with photodegradation products of fenoxycarb, the IGRs methoprene and pyriproxyfen, and a variety of pesticides including the pyrethroids fenvalerate and cypermethryn, the phenoxyacetic acid herbicide 2,4-D, DDT, and the nitrodiphenyl ether herbicides acifluorfen and fluorodifen. 相似文献
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The Dualex is a new leaf-clip instrument that can be used to monitor corn nitrogen (N) status. It is based on the measurement of polyphenolics (Phen), which are secondary metabolites affected by stress factors. The purpose of this study was to compare Dualex to SPAD (chlorophyll meter), the latter having been used for several years in monitoring crop N status. As well, the interest of combining Dualex and SPAD information in Chl/DUAD (ratio of SPAD to Dualex reading on adaxial side), Chl/DUAB (ratio of SPAD to Dualex reading on abaxial side), and Chl/Phen (ratio of SPAD to the sum of DUAD and DUAB) ratios were considered. Significantly positive and negative correlations with corn leaf N concentration were found for SPAD and Dualex, respectively. Successful N status diagnosis could be achieved with either Dualex or SPAD for corn within 21 days after topdressing while the Dualex lost sensitivity at later stages. Dualex measurements could be limited to leaves abaxial side or adaxial side, instead of adaxial + abaxial sides, with no inconvenience. Among all parameters considered, the combined ratios with SPAD (Chl) and Dualex readings, Chl/DUAD, Chl/DUAB, and Chl/Phen were strongly related to applied N dose at all samplings dates, and found the most sensitive and robust through the season. 相似文献
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蒸散发(ET)作为影响水资源空间分布的关键因素之一,准确监测、模拟其值的空间变化,对提高水资源利用效率和保护区域生态环境具有重要意义.选择北方典型草原区锡林河流域作为研究对象,通过气象数据和TM数据,利用遥感和GIS技术,构建了锡林河流域反演蒸散发的SEBAL模型.结果显示,卫星过境当天流域蒸散发为0～9.1 mm/d,其中蒸散发在0～2 mm/d之间的像元占流域总面积的70％以上,地表水资源不足是导致蒸散发较小的主要原因;按照土地利用类型统计,水域分布的地区日蒸散发相对较高,草地分布的地区日蒸散发相对较低;相关性分析显示,地表温度的大小变化对ET空间分布影响较大.反演结果对流域尺度的水资源管理定量化研究具有重要意义,同时,可为深入研究“水—草 畜”系统平衡奠定理论基础. 相似文献
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M. Tschapek 《植物养料与土壤学杂志》1984,147(2):137-149
Except for dehydroxylated silica, all the inorganic minerals of soils are hydrophilic because their surfaces usually hold ions and polar groups (hydroxyls). The molecules of humic acid, i. e. the most important part in soil humus, are amphiphilic and superficially active. Water repellancy in soils is mainly caused by amphiphilic humic acid. Criteria are supplied to characterize the hydrophilic-hydrophobic balance of soils. The changes in the hydrophilicity-hydrophobicity of soil by the addition of organic components modify many of their hydric properties, such as wetting, evaporation, infiltration, etc. which are frequently incompatible. Due to the many different types of soil and organic correctors, no general recommendations can be made. 相似文献
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随着社会经济的发展，人类活动对滑坡灾害的影响日益显著，而土地利用方式是人类活动的集中体现，因此，有关土地利用方式对滑坡发生发育影响的分析将成为滑坡防治研究中的一项重要内容。本文分析了滑坡发生的三种基本机制，并按照滑坡发生的机制，探讨了三种基本土地利用方式对滑坡的影响原理。 相似文献
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Condo AM Baker DC Moreau RA Hicks KB 《Journal of agricultural and food chemistry》2001,49(10):4961-4964
Phytosterols and phytostanols are known to lower low-density lipoprotein-cholesterol (LDL-C) levels in humans by up to 15%, and at least two products, Benecol and Take Control, are now on the market as naturally derived fatty acid esters of phytostanols (stanol esters) and phytosterols (sterol esters), respectively. A synthetic process was developed to synthesize gram quantities of trans-feruloyl-beta-sitostanol from ferulic acid and beta-sitostanol, with high purity and yields of approximately 60%. The process involves (a) condensation of trans-4-O-acetylferulic acid with the appropriate phytostanol or phytostanol mixture in the presence of N,N-dicyclohexylcarbodiimide and 4-(dimethylamino)pyridine, (b) separation of the trans-4-O-acetylferuloyl products by preparative liquid chromatography, (c) selective deacetylation of the feruloyl acetate, and (d) chromatographic purification of the feruloylated phytostanols. The process was successfully applied to synthesize stanol trans-feruloyl esters from "Vegetable Stanols", a mixture of approximately 70:30 beta-sitostanol and beta-campestanol, in comparable purity and yield. 相似文献
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Use of the enantiomeric composition for the assessment of the authenticity of fruit beverages 总被引：1，自引：0，他引：1
Ruiz del Castillo ML Caja MM Herraiz M 《Journal of agricultural and food chemistry》2003,51(5):1284-1288
Enantiomeric compositions of chiral terpenes in commercial fruit beverages were examined by solid phase microextraction-gas chromatography (SPME-GC). Optimization of the method was accomplished on the basis of some parameters involved in the extraction, such as heating temperature and extraction time, that provided the highest peak areas, 60 degrees C and 2 min being the optimal values. With the proposed method relative standard deviation (RSD) values from three replicates ranging from 2 to 12% were obtained. The enantiomeric distribution of some terpenes remained constant, whereas other terpenes (linalool, terpinen-4-ol, and alpha-terpineol) exhibited a considerable variation among samples. This can be indicative of the eventual addition of aromas to some fruit beverages. 相似文献
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《广西农业生物科学》2010,(2):203-205
DNA双螺旋结构的发现和重组DNA技术、PCR技术的产生极大的促进了分子遗传学的发展。几十年来,DNA一直被认为是决定生命遗传信息的主要物质。但是,大量的事实表明,生命遗传信息从来就不是基因所能完全决定的。例如,同卵双生的双胞胎具有完全相同的基因组,在相同的环境下长大后,他们在性格、健康等方面都会有较大的差异,这并不符合经典遗传学理论预期的情况,让人产生疑问; 相似文献
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