Crop demand of manganese

The objectives of this study were to evaluate some of the popular rotation crops grown in Hungary for tolerance to low external Mn(2+) levels and to determine the critical tissue concentration of Mn(2+) deficiency during early stages of growth. The minimum Mn(2+) concentration required in soil nutrient contents was 42.5 mg kg(-1) for sunflower, 24.3 mg kg(-1) for tobacco and 10.2 mg kg(-1) for triticale. Sunflower, tobacco and triticale achieved optimum growth at 48.0-65.0 mg Mn(2+) kg(-1), 24.9-32.1 mg Mn( n+) kg(-1) and 28.7 to 29.6 mg Mn(2+) kg(-1), respectively. Critical shoot Mn(2+) concentration at early stages of growth was 53.6 mg kg(-1) in sunflower, 458.0 mg kg(-1) in tobacco and 193.8 mg kg(-1) in triticale. Our results demonstrate that the tolerance to low external Mn(2+) (triticale: <30.2 mg kg(-1); sunflower: <56.2 mg kg(-1); tobacco: <69.3 mg kg(-1)) and the critical tissue Mn(2+) levels for deficiency varied significantly between crop species tested.     

Rethinking Crop Genetic Resource Conservation

Abstract: A worldwide system of crop germplasm conservation has been developed around ex situ preservation This system is based on a dual mandate of conservation and development; and it has largely ignored the farming systems that produce germplasm A revisionist critique of the existing system is presented Problems of the current strategy include incomplete collection loss within these collections, isolation from evolutionary processes, and budgetary constraints. In situ conservation offers an alternative to current methods, especially if conservation rather than development is the priority. The concept of genetic erosion is discussed and evaluated in light of recent evidence of uneven change in areas of crop diversity. Farmers in many parts of the world are conserving traditional varieties even as they modernize and adopt improved varieties. This pattern is illustrated by reference to Asian rice agriculture. A new approach to conservation is needed that builds a collaborative program between farmers, crop scientists, ecologists, biogeographers, and social scientists. A first step is to analyze farming systems that already conserve traditional crop varieties.     

Effect of Polymeric Coatings On Phytoplankton Standing Crop

Some polymeric marine coatings based on vinylcopolymer and linseed oil have been prepared in the laboratory and their efffect on phytoplankton standing crop was tested. the coating is prepared either from vinylcopolymer or linseed oil or a mixture of both binders with 1:1, 1:2 and 2:1 ratios in the presence or absence of a soluble resin. the coatings were applied to glass slides and tested in a sea water medium. Also, correlations between the weight of the coating film and numbers of phytoplankton species were calculated. the results showed no correlation between the weight of films of either vinylite or oil binders and the total number of all phytoplankton species, but significant correlation was found for some phytoplankton species, such as Thalassiosira decipiens. the weight of the film coating of vinylcopolymer in the presence of soluble resin with 1:1, 1:2 and 2:1 ratios is significantly correlated to the total number of phytoplankton and some other dominant species. Formulations of linseed oil and a soluble resin with 1:1, 1:2 and 2:1 ratios are correlated to the numbers of Chaetoceros affinis, Bellorochea malleus and Skeletonema costatum.     

农业秸秆在杏鲍菇生产中的应用

利用花生秸、玉米秸、甘薯藤配以棉籽壳、麸皮作为杏鲍菇栽培基质,以w(棉籽壳)=80%、w(麸皮)=20%作为对照配方,研究了 6种秸杆配方的培养料对杏鲍菇生长发育和产量的影响.结果表明:不同配方培养料对杏鲍菇的菌丝生长速度和生长势、生产周期、产量和生物学效率均有较大影响;玉米秸、花生秸是杏鲍菇优良的营养基质,其中,以玉米秸粉和棉籽壳为主料的培养料更适合杏鲍菇生长,其菌丝生长速度快,生长势最强,出菇较快,且产量最高,生物学效率町达60%以上.综合出菇后菌渣作为动物饲料原料的适口性来考虑,以w(棉籽壳):30%、w(玉米秸粉)=50%、w(麸皮)=20%的配方为最佳.     

Uranium Accumulation of Crop Plants Enhanced by Citric Acid

Citric acid was applied to soil to enhance U accumulation in four crop plants. While the highest enhanced U accumulation of aboveground tissues (a.c. 2000 mg kg⁻¹ dry weight) occurred in the leaves of Indian mustard (Brassica juncea), the highest enhanced U accumulation of roots (a.c. 3500 mg kg⁻¹ dry weight) occurred in canola (Brassica napus var. napus). Uranium translocation among tissues of test plants is in the relation of roots>shoots ≅ leaves. The flowers of sunflower (Helianthus annuus) contained similar or higher U concentrations than those found in shoots, but concentrations in seeds are close to zero. In conclusion, Indian mustard is recommended as a potential species for phytoextraction for U-contaminated soil due to its high U accumulation of aboveground biomass (a.c. 2200 μg per plant). There is no evidence that two types of soils cause a significant difference of the enhanced U accumulation (p<0.05). Results, however, indicate that additional citric acid may result in downward U migration that may contaminate groundwater. Speciation of U that is taken up by plants is also discussed in the end.     

Potato Diversity in the Andean Center of Crop Domestication

The diversity and population structure of potato landraces ( Solanum spp.) within their center of domestication was studied using isozyme surveys of four polymorphic loci. The objective in assessing the distribution of genetic diversity was to assist in planning conservation strategies of crop genetic resources that are threatened by genetic erosion. In situ conservation methods depend on this type of analysts. Research was conducted in the region of Cusco, Peru. Eight fields spread among two microregions were randomly sampled, and 610 tubers were studied from this sample. In addition, 503 tubers were collected from markets in seven different meso-regions (provinces) surrounding the regional center of Cusco. Thirty genotypes were identified in the field sample and 82 in the regional sample. The frequency and distribution of genotypes and alleles are described. A high degree of genotype endemism was found at both the field and regional levels. Genotypes were unevenly distributed, and most of the genotypic diversity was between rather than within populations. At the allele level, however, we found that a very high percentage of the diversity was within rather than between populations. The genotype is the key unit for maintaining the population of potato landraces. Our findings suggest that collections need to be both geographically extensive and intensive. Because farmers are able to maintain most alleles on relatively small portions of their land, in situ conservation is a viable strategy.     

粉煤灰对土壤和作物生长的影响

粉煤灰施用量控制在60～600t／hm2,不会造成土壤、粮食的污染,且能改善土壤的物理、化学和生物学性质．有利于养分的转化。粉煤厂磁化后15～7．5t／hm2的施用量即可达到最佳的改上增产效果。本文在分析粉煤灰埋化性质的基础上,讨论了粉煤灰对土壤和作物生长的影响,同时也提出了降低粉煤灰中有害物质对土壤和作物不利影响的农用技术。     

农作物秸秆酶解与磷细菌肥的生产

以农作物秸秆为酶水解原料 ,用纤维素酶进行酶水解 ,水解液用于培养磷细菌肥生产菌 ,再用粉碎至一定粒度的作物秸秆对培养菌液进行吸附。实验结果表明 ,经酶解得到的水解液在添加一定的辅料后 ,可以作为培养磷细菌的料液。适宜条件下 ,菌量可达 5 1× 1 0 8/ml。     

二氧化锰体系中环丙沙星的氧化转化研究

为了更全面的了解环丙沙星在自然界中的环境化学行为,采用批处理实验方法研究了环丙沙星在二氧化锰作用下的氧化转化过程,并讨论了溶液的pH对反应的影响。结果表明,在无二氧化锰的条件下,环丙沙星的质量浓度在1周内检测没有明显的变化。在二氧化锰存在的条件下,环丙沙星对二氧化锰的氧化作用具有较强的反应感受性。pH一定的条件下,当环丙沙星相对过量时,环丙沙星去除率随自身质量浓度的增大而减小,随二氧化锰质量浓度的增大而增大。此外,随着溶液pH值由3.5升至5.9时,环丙沙星的去除率显著上升。     

二氧化锰体系中环丙沙星的氧化转化研究

为了更全面的了解环丙沙星在自然界中的环境化学行为,采用批处理实验方法研究了环丙沙星在二氧化锰作用下的氧化转化过程,并讨论了溶液的pH对反应的影响。结果表明,在无二氧化锰的条件下,环丙沙星的质量浓度在1周内检测没有明显的变化。在二氧化锰存在的条件下,环丙沙星对二氧化锰的氧化作用具有较强的反应感受性。pH一定的条件下,当环丙沙星相对过量时,环丙沙星去除率随自身质量浓度的增大而减小,随二氧化锰质量浓度的增大而增大。此外,随着溶液pH值由3.5升至5.9时,环丙沙星的去除率显著上升。     

Benthic recruitment and manganese crust formation on seamounts

Hydrogenous ferromanganese crusts are a common feature of oceanic seamounts, forming slowly (predominantly at 1 to 5 mm/m.yr through precipitation from seawater, by a process that is poorly understood yet producing crusts of thicknesses up to 240 mm. It remains unexplained why crusts are not overwhelmed by more rapid biological processes occurring simultaneously. The present study of recruitment by sessile invertebrates to ferromanganese crusts and basalt on Cross Seamount (18°40N; 158°17W), North Pacific Ocean, from July 1988 to February 1990 supports the view that hydrogenesis alone may not adequately account for crust formation. Here, mediation of crust growth by benthic Foraminifera and inhibition of ferromanganese oxide precipitation by high abundances of sessile macrofauna are suggested as two interactive biological processes relevant to crust accretion. Larval supply is an important factor in the distribution of sessile macrofauna on oceanic seamounts.     

Amorphous oxides of manganese as new sorbents of strontium ions

Samples with the best adsorption properties are selected as a result of investigations conducted on synthesis of manganese-dioxide-based materials and study of their physicochemical properties. Materials were selected on the basis of their low cost and the simplicity of their production technology. In the laboratory the synthesis and analyses of materials was carried out for selected samples. The sorption of a series of elements is studied for a more detailed investigation of materials obtained. The results obtained will promote the synthesis of materials with improved adsorption properties with the aim of their application for purification of water from strontium. It is shown that the most promising way for amendment of manganese oxide is modification of this material using acid-resistant oxides. These oxides are also less expensive than existing sorbents for strontium.     

绿磺隆在土壤中的残留及其对后茬作物的安全性

研究了绿磺隆在江苏省吴县及河北省石家庄市麦田土壤中的降解规律 ,以及水稻对绿磺隆的敏感性。结果表明 ,绿磺隆在土壤中残留期较长 ,在江苏省吴县及河北省石家庄市麦田土壤中的降解半衰期分别为 2 2 82和 3 2 98d ;水稻对绿磺隆极为敏感 ,它对水稻根系生长的抑制浓度仅为 0 1 μg/kg,麦收后土壤中残留的绿磺隆极易对后茬水稻产生危害。     

Estimating net benefits of recreation under conditions of excess demand

The public provision of outdoor recreation necessitates the development of nonmarket measures of the value of resources in recreational use. Such values can be used as surrogates for market values in the decision-making process. Another aspect of recreation as a publicly provided good is the absence of a mechanism to eliminate automatically excess demand. The absence of such a mechanism has resulted in conditions of excess demand at many recreation sites.This paper deduces the implications of excess demand for the travel cost method of benefit estimation. We show that when excess demand results in rationing at a particular site, the travel cost method will underestimate the true benefits of the site. The results are important because they help identify the direction of bias of one measure of the benefits from the use of a natural resource.     

Crop substitution in the estimation of economic benefits due to ozone reduction

Prior estimates of economic loss from ozone damage to food crops have not allowed for farmer substitution in inputs—and particularly have not allowed for acreage shifts between crops—in response to yield changes. This is a potentially serious problem since benefits from air pollution control legislation may also be estimated without allowing for this direct substitution. This study explores how much acreage shifting might occur between corn, soybeans, and wheat if ozone were reduced to background levels, and how such substitution might affect the estimation of benefits from ozone reduction.     

赤红壤不同轮作形式的效益研究

赤红壤不同轮作形式的效益研究吴锦暖，程汝饱（广东省土壤研究所，广州ｓｌｔｈｅ）ＳｔｕｄｙｏｎＢｅｎｅｆｉｔｓｏｆＤｉｆｆｅｒｅｎｔＣｒｏｐＲｏｔａｔｉｏｎＰａｔｔｅｒｎｓｉｎＬａｔｏｒｅｄＳｏｉｌＵｔｉｌｉｚａｔｉｏｎ．￥ＷｕＪｉｎｎｕａｎａｎｄＣｈ...     

Benzene conversion by manganese dioxide assisted silent discharge plasma

Non-thermal plasma technologies have shown their promising potential specially for the low concentration of volatile organic compound control in indoor air in recent years. But it is also high energy consuming. So, to improve the energy efficiency, adding catalysts which enhance the plasma chemical reactions to plasma reactors may be a good selection. Therefore, in this study the manganese dioxide assisted silent discharge plasma was developed for benzene conversion at a relatively high energy efficiency. The results show that MnO₂ could promote complete oxidation of benzene with O₂ and O₃ produced in the plasma discharge zone. The energy efficiency of benzene conversion with MnO₂ was two folds as much as that without catalysts. It was also found that the site of MnO₂ in the reactor and the energy density had effects on benzene conversion. While the energy density was lower than 48 J/L, benzene conversion decreased with the increase in the distance between MnO₂ bed and the plasma discharge zone. Whereas when the energy density was higher than 104 J/L, benzene conversion had an optimal value that was governed by the distance between MnO₂ bed and the plasma discharge zone. The mechanism of benzene oxidation in plasma discharges and over MnO₂ is discussed in detail.