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高寒草甸土壤腐殖质组成及性质的研究 总被引：1，自引：0，他引：1
不同草甸植被下土壤有机质含量不同，同时腐殖质特性亦有较大差异。采用熊田法研究表明，不同类型的草甸土壤总腐殖质含量高低变化较大，总有机质含量变化在７．００％～１２．２８％之间，游离胡敏酸比率为５１．６７％～６０．１０％，游离富里酸比率为８０．０１％～８６．４６％；可提取腐殖质中胡敏酸所占经率为４７．９９％～５６．９８％。此外腐殖质相对色度、Ｅ４、也不明显差异。 相似文献
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R. Pellek 《Agroforestry Systems》1992,17(2):135-152
Management of hillside cropland is a critical issue in the tropical world because of the extreme pressure on the land itself
that results from the decision to farm what would be considered in many countries as marginal land.
Practices such as contour hedgerows and other soil conservation techniques could be more effective if they are installed or
aligned in such a way that they maximize the land capability potential in various sectors of typical soil catenas; and if
biological control crops including trees, grasses and shrubs are spatially arranged to take advantage of their intrinsic biological
potential to accommodate to the edaphic dissimilarities of steep hillsides.
Spatial arrangements of annual and perennial crops in natural geosequences are discussed, and suggestions are given on how
spatial considerations can be matched to preferred crop mixes of trees, shrubs and grasses, in an attempt to halt erosion
and better protect the environment. Land use planning on a physiographic and soil capability basis is proposed, but acknowledges
that effective implementation is subject to a determined campaign to extend both the theory of sound land management and the
provision of technical assistance to peasants to demonstrate the concepts and to interpret the results of the practices.
This paper explores certain aspects of physiographic and edaphic similarities and constraints of peasant farming practices
on steep slopes, and offers some theoretical bases upon which hedgerow technology can be applied to improve water and plant
relations, ameliorate environmental effects and be initiated by individual farmers at little cost. A range of other soil conservation
or agroforestry techniques, as used in Haiti is described; and a simple monitoring or measurement model to determine the amount
of soil saved is provided, and the possibility of teaching the methods to minimally trained field technicians is explored,
pursuant to encouraging farmers to give greater attention to the value of soil conservation and proper land use planning.
Presented at the 6th International Soil Conservation Organization Conference, Soil Conservation for Survival, Addis Ababa,
Ethiopia, 6–18 November 1989 相似文献
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[目的]研究日间UV—B辐射对黄瓜穴盘苟生长发育的影响,寻求最佳的照射时长,以达到培育壮苗的目的、[方法]以黄瓜品种“露地二号”为试验材料,通过不同时长UV—B照射试验、【结果】结果表明,照射2h没有作用;照射3h即可有效抑制黄瓜苗徒长,叶绿素含量提高;照射4h虽然有抑制幼苗徒长的作用,但苗期全株干鲜重、定植30d后的株高、茎粗和果实产量均低于3h。[结论]日间补充照射UV—B辐射的最佳时长为3h。 相似文献
4.
B.A. Naaijkens A. van Dijk E. Meinster K. Kramer O. Kamp P.A.J. Krijnen H.W.M. Niessen L.J.M. Juffermans 《Research in veterinary science》2014
The Wistar rat is a commonly used strain for experimental animal models. Recently it was shown that results vary between studies using Wistar rats of different suppliers. Therefore we studied whether Wistar rats obtained from Harlan Laboratories (Ha, n = 24) and Charles River (CR, n = 22) had a different outcome in an acute myocardial infarction (AMI) model. AMI was induced in both Ha and CR Wistar rats by one operator. This resulted in a significantly higher survival rate for Ha (79.2 ± 10.2%) compared with CR rats (54.2 ± 10.2%, p < 0.05). Furthermore, CR rats had lost significantly more weight after 7 days (−5.9 ± 3.1%) compared with Ha rats (−0.8 ± 1.7%; p < 0.001), indicating a worse health status of the CR rats. Paradoxically, the induced infarct was smaller in CR rats (7.3 ± 3.6% of the heart) compared with Ha rats (12.1 ± 4.7%, p < 0.05). This indicates that CR rats were less sensitive for the cardiomyocyte damage subsequent to AMI induction, but remarkably showed more clinical side effects indicating that Wistar rats from two suppliers had a different response within the same AMI model. 相似文献
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Cereal cyst nematodes ( Heterodera avenae Woll.) are economically damaging barley parasites in most cereal growing areas of the world and the development of resistant cultivars is the best measure against the pathogen. An ISSR (inter-simple sequence repeat) marker identified as closely linked with the H. avenae race 1 and 2 resistance gene ( Ha2 ) has been converted into a codominant sequence characterized amplified region marker ( Ha2S18 ) and mapped in barley 'SW Buddy' × 'SW Cecilia' DH population at 4.3 cM from the Ha2 locus on the long arm of chromosome 2H. The potential usefulness of Ha2S18 in large scale marker assisted selection schemes has been evaluated in a broad genetic background and is an important complement to the bioassay and to other linked DNA-markers for this trait. 相似文献
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利用替代寄主生产马尾松毛虫质型多角体病毒的研究 总被引：7，自引：0，他引：7
ＤｐＣＰＶ对８种鳞翅目昆虫感染试验结果表明，棉铃虫最敏感，感染率达９７．０％。ＤｐＣＰＶ对棉铃虫的毒力ＬＣ５０＝７．６５×１０４ＣＰＢ／ｍｌ，浓度与感染死亡率相关性及回归方程均达到显著性。ＨａＤｐＣＰＶ与原毒种ＤｐＣＰＶ的形态特征相同；棉铃虫可用人工半合成饲料配方２在小塑料盒内单虫饲养，幼虫成活率达９８％以上、羽化率达９０％，平均蛹重０．４００６ｇ，平均产卵量７９７．７粒，卵孵化率达９８．２％；ＨａＤｐＣＰＶ对第一代４～５龄马尾松毛虫的毒力较强，ＬＣ５０＝１．１４×１０４ＣＰＢ／ｍｌ，与原毒种相比，毒力没有下降。用棉铃虫来生产ＤｐＣＰＶ，采用２３～２６℃、３龄虫、使用浓度１０５ＣＰＢ／ｍｌ以上，是比较理想的组合。将病毒喷在人工饲料表面喂虫，可获得较高的病毒产量，平均每条虫可产８．１３亿ＣＰＢ，与用原宿主生产的产量相接近。用ＨａＤｐＣＰＶ防治第一、二代４～５龄马尾松毛虫，防治效果达６０．２％～８４．０％。 相似文献
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《Soil Science and Plant Nutrition》2013,59(3):342-352
Abstract Water-soluble ionic substances in acid sulfate soils are likely to be strong controls for crop production and to have impacts on aquatic ecosystems. In dry seasons, in particular, oxidation of the soil surface followed by acidification probably produces lots of acids and soluble metals. To estimate acid and metal loads from acid sulfate soils to aquatic environments, we determined the composition of water-soluble ions from soils distributed in the Mekong Delta, Vietnam. At the end of the dry season, soils were taken from each soil horizon in two soil profiles on the delta under different land developmental processes. Water-soluble ions were extracted using both distilled water and artificially synthesized irrigation water (pH 6.3) adjusted to the same ionic strength and pH as the field canal water. The relationship between extracted basic cations in both extracts showed high linear correlation, indicating a similar extraction mechanism between both extractants. Higher ionic strength in the artificial irrigation water may not have any advantages for extraction by ion exchange and, thus, properties of extracts are likely to depend on the soil properties. The older the soil parent material, the larger the rates of soluble Al and Fe and the lower the pH. Progressive weathering of the soil on the older delta has already discharged greater amounts of bases, probably for compensation of acids, and the soil has started to release exchangeable Al sorbed onto negative-charge colloids and Fe from decomposed oxides. The soil profile of the older delta released relatively greater concentrations of Al with a lower content of base cations, where the annual averaged rice yield was half that of another site. Soluble metals and acids at both sites appear to accumulate in the upper horizons above the low permeable layer, which is probably widely distributed in the Mekong Delta. 相似文献
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