Phosphorus sorption maxima and desorbability in selected soils with andic properties from the Azores, Portugal     

E. Auxtero  M. Madeira  E. Sousa 《Geoderma》2008,144(3-4):535-544

P sorption and desorption capacities were determined on 30 soil horizons (surface and subsurface) of soils with andic properties from the Azores, Portugal, using the Langmuir equation and successive extractions with dilute calcium chloride (CaCl₂), respectively. The proportion of P recovery (Prec) using distilled water (H₂O), CaCl₂, Bray 2 (B2), Mehlich 3 (M3), Egnér–Riehm (ER) and Olsen (OL) extractants was also determined to assess the extent of P release from soils enriched with P at P sorption maxima (Pm). Soils containing very low amounts of organic C and allophane (Vitrandic Haplustepts and Vitrandic Udorthents) showed the lowest values of Pm (48–565 mg kg^− 1) and the highest values of P desorbability (Pdes) (69–100%), indicating that P can be easily lost from these soils. Application of fertilizers to these soils should be restrained in order to minimize eutrophication risk of nearby water bodies. In contrast, allophanic and non-allophanic horizons of Typic Placudands, Alic Hapludands, Acrudoxic Hapludands and Acrudoxic Hydrudands showed much higher values of Pm (2273–52,400 mg kg^− 1) and lower values of Pdes (4–57%).They also showed low proportions of Prec by the used extractants, indicating that large amounts of P can be sorbed in an unavailable form. Thus, these soils may require large amounts of P fertilizers and an efficient method of P application. Other studied soils with high amounts of 1:1 layer silicate minerals and having weak andic properties (Typic and Andic Haplustepts), showed intermediate Pm (1124–8333 mg kg^− 1) and Pdes values (20–63%).

The values of Pm were positively correlated with Al_d, Al_o, allophane, Fe_o, Fe_d and Al_p contents, and with the values of Al_o + 1/2 Fe_o. In contrast, values of Pdes were negatively correlated with these soil constituents. Of the six extractants, the B2 extractant showed generally higher proportions of Prec than the other extractants in most studied soils. The proportions of Prec by the B2, M3, ER and OL extractants were negatively correlated with contents of Fe_o, Fe_d, Al_d, Al_o, Al_p, and Fe_p, and with the values of Al_o + 1/2 Fe_o and PR.  相似文献   

Biomass,nodulation and N2 fixing response by subclover and pink serradela to phosphorus fertilization     

Ana Cristina Boucho  Ramón Redondo  Fátima Calouro  Manuel Madeira 《Archives of Agronomy and Soil Science》2019,65(10):1431-1445

In Mediterranean areas, sustainable production of rainfed pastures is associated with plant species which withstand low soil fertility and variable annual drought, phosphorus (P) being the primary limiting nutrient for legume growth and N₂ fixation. A study was undertaken under environmentally controlled conditions to compare the response of subclover and pink serradela to P supply using a moderately acid soil, very poor in available P, in terms of biomass, nodulation pattern, N₂ fixation and P use efficiency. A P dose in the range of 30–60 kg P ha^?1 is recommended as a starter for pastures under the present conditions. A higher P rate reduced the fixing nodule number and biomass, and the N₂ fixation rate. Fixed N₂ per unit of nodule P by pink serradela as monocrop was about 80% greater than the sole subclover, demonstrating its higher efficiency on the use of nodule P. Thus, pink serradela needs a lower P rate to produce the same amount of biomass per unit area as sole subclover. Long-term studies in field conditions, using these and other new pasture legume species are needed to consolidate the present findings.  相似文献   

Effects of insecticides on thermotropic lipid phase transitions     

M.C. Antunes-Madeira  A.P. Carvalho  Vítor M.C. Madeira 《Pesticide biochemistry and physiology》1980,14(2):161-169

The organophosphorus insecticides, parathion and azinphos, significantly lower the midpoint temperature of thermotropic phase transitions of lipid bilayers, but malathion has no effect. The effects of parathion and azinphos are more pronounced on bilayers of short-chain lipids. These compounds induce phase separations in binary lipid mixtures containing dimyristoyl and distearoyl phosphatidylcholines, although similar effects could not be noticed in mixtures of dimyristoyl phosphatidylcholine and dimyristoyl phosphatidylethanolamine. Furthermore, the compounds partially restore phase transitions abolished by cholesterol. It is concluded that parathion and azinphos induce molecular disorders in lipid bilayers, either by having fluidizing effects or by promoting phase separations as a consequence of preferential interaction with more fluid lipids. The interaction of the compounds with cholesterol-containing bilayers produces phospholipid-rich lateral domains.  相似文献   

Driving factors determining the occurrence of sodic soils in dry subhumid Mediterranean areas     

Fernando Manuel Monteiro  Maria Madalena Fonseca  Manuel Armando Madeira  Adrien J. Herbillon 《植物养料与土壤学杂志》2012,175(1):94-100

An evaluation of the factors determining the occurrence and the properties of soils with low permeability occurring in vast areas in S Portugal was carried out taking into account the terrain morphology and the geology of the region. This paper deals with the variation patterns of the physical and chemical characteristics of soils from several soil toposequences that occur under different gradient slopes and on different parent rocks. Spatial variation of soil properties mainly depends on the composition of their cation‐exchange complex, as the role of other factors, such as the mineralogy of the clay fraction, were of minor importance. There is often a stronger increment of Na and/or Mg than of Ca with depth, causing a variable degree of sodicity in some of these soils, to which waterlogging tendency of their upper horizons is related. Though the occurrence of these features is determined by the nature of the parent rock, their degree of expression varies primarily according to the topographic position of soils. Therefore, a catenary distribution including nonsodic Cambisols or Luvisols in the hillcrests and Stagnic Solonetz or Sodic Luvisols or Sodic Stagnosols in the topographic lows is common. Such soil characteristics are of utmost importance for irrigation suitability and management of these soils, and for environmental impacts assessment, as the region is vulnerable to desertification.  相似文献   

Effects of site preparation and slash management on growth and understory vegetation of Eucalyptus globulus plantations along a rotation time span in Portugal     

M. Carneiro  A. Fabião  M. Madeira 《European Journal of Forest Research》2014,133(5):941-955

The removal or maintenance of harvest residues in eucalypt plantations may influence site quality and productivity. Removal of slash from the site may facilitate further management operations and provide a valuable energy resource, but effects on site productivity and sustainability for a rotation time span were not yet assessed under Mediterranean conditions. Therefore, a study was carried out to assess the effects of slash (harvest residues plus forest floor litter) management and soil preparation options on stand productivity and understory vegetation dynamics, hypothesizing that those options influence tree growth, forest floor dynamics and understory biomass and diversity. An experiment was installed in West Central Portugal, consisting on: removal of slash without soil preparation (R); broadcast of harvest residues on the soil surface without soil disturbance (S); as in S, but concentrating the woody debris between tree rows (W); incorporation of slash into the soil by harrowing (I); removal of slash followed by harrowing (RH); and as in I followed by ripping (IS). The experiment was monitored for a rotation time span (140 months). Maintenance of slash followed by deep soil disturbance led to the highest wood production, but differences between treatments were not significant (p > 0.05). Forest floor load and understory biomass were also similar between treatments. Ground vegetation played an important role on nutrient cycling in early rotation stages, such effect being irrespective on slash management options. Incorporation of slash into the soil followed by ripping is probably the best option to match production and environmental sustainability of eucalypt plantations in Mediterranean conditions.  相似文献   

Reverse phase liquid chromatographic determination of dexamethasone acetate and cortisone acetate in bulk drug substances and dosage forms: method development     

L L NG 《Journal of the Association of Official Analytical Chemists》1987,70(5):829-833

The determination of the steroid acetates was evaluated for ruggedness of the method by using an octyldecylsilane column, 254 nm detection, and acetonitrile-water as mobile phase. Mobile phase pH, oven temperature, and columns from various manufacturers had no dramatic effect on the chromatography. The method was then optimized for dexamethasone acetate and cortisone acetate bulk drug and dosage forms. For dexamethasone acetate, the bulk drug substance should be dried at 105 degrees C before use, and the sample should be dissolved in 50% acetonitrile-buffer pH 6 for stability. Cortisone acetate, on the other hand, was found to be nonhygroscopic and hence could be used as received. For stability, the sample should be stored in 50% acetonitrile-buffer pH 4.  相似文献   

成年猪结肠肥大细胞的分布     

王家鑫  李景宇  张福君  张海旺  苏建清 《中国兽医杂志》2001,37(9):7-8

成年猪结肠按常规制备石蜡切片,用甲苯胺蓝改良法显示肥大细胞.结果粘膜型肥大细胞(MMCs)主要分布于固有膜深层,不同部位结肠粘膜中MMCs的数量存在极显著差异(P＞0.01),结缔组织型肥大细胞(CTMCs)主要分布于粘膜下层且不存在数量上的区域性差异(P＞0.05).结论猪结肠MMCs的分布类型具有区域异质性特征.  相似文献   

不同价态外源硒对冬小麦生长及生理代谢的影响   总被引：5，自引：1，他引：5       下载免费PDF全文

付冬冬  王松山  梁东丽  缪树寅  段曼莉  胡斌 《农业环境科学学报》2011,30(8)

用盆栽试验研究了不同浓度外源硒(四价和六价)处理土壤对小麦生长和生理代谢的影响,旨在为富硒小麦的种植和开发提供理论依据。结果表明:外源硒抑制了苗期小麦的生长(株高和生物量);而在生长后期,随外源硒浓度增加表现为先促进后抑制作用。Se(Ⅳ)和Se(Ⅵ)处理对小麦生物量影响的EC10分别从苗期的1.40mg·kg-1和0.28mg·kg-1增加到收获期的28.48mg·kg-1和4.56mg·kg-1,表明小麦对硒的耐受浓度随生长时间的延长逐渐增大。Se(Ⅵ)低浓度(≤1mg·kg-1)对小麦生长的促进作用及高浓度(≥2.5mg·kg-1)对小麦生长的抑制作用均大于Se(Ⅳ)。小麦籽粒产量随外源Se(Ⅳ)和Se(Ⅵ)浓度的增大先升高而后降低,分别在2.5mg·kg-1和1mg·kg-1浓度处理时达到最大。低浓度硒处理(Se(Ⅳ)≤5mg·kg-1和Se(Ⅵ)≤0.5mg·kg-1)能促进拔节期小麦叶片中GSH和POD等抗氧化酶活性,显著降低叶片过氧化物质MDA(Se≤2.5mg·kg-1)含量,高浓度硒处理则与之相反。  相似文献   

采用分子生物学技术分析不同施肥土壤中细菌多样性   总被引：3，自引：1，他引：3  

吴展才  余旭胜  徐源泰 《中国农业科学》2005,38(12):2474-2480

 本研究探讨在小白菜栽培时，分别添加果蔬加工废弃物生产的堆肥和化肥对土壤微生物区系的影响。利用扩增16S rRNA基因来比较微生物群落的技术，分离出所有群落DNA，再以此DNA为模板，以专一性引物扩增出16S rRNA基因（rDNA）。随后建立16S rDNA基因文库后，再以计算机仿真的方式，选出能将上述引物扩增的16S rDNA基因中间切割成片段长度范围集中的一组限制性内切酶--AciI、BstUI、和RsaI。结果表明，无施肥土壤与添加堆肥土壤中微生物较接近。无施肥、添加堆肥、添加化肥土壤三者的微生物多样性指数分别为0.990、0.986和0.962；均匀度为0.979、0.977和0.931。  相似文献   

油乳剂灭活疫苗不同接种途径的效力比较试验     

张建伟  李林  章振华  景小冬  黄凤军  王惠云  姜北宇 《畜牧与饲料科学》2011,32(1):77-78

采用北京市农林科学院畜牧兽医研究所免疫预防研究室制备的鸡新城疫、传染性支气管炎、减蛋综合征、传染性脑脊髓炎四联灭活疫苗,分别经颈背侧皮下、胸部肌肉及腿部肌肉共3个部位免疫SPF鸡,免疫后采血,测定ND、IB、EDS HI抗体,并用AEV VR株强毒攻击,攻毒后观察疫苗保护效果,比较不同接种部位对油乳剂灭活疫苗效力的影响。结果证明,经颈背侧皮下、胸部肌肉及腿部肌肉3个部位免疫均可产生同样好的免疫效力。  相似文献