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991.
We performed a comparative experiment to investigate: (1) how the ubiquitous soil bacterium Bacillus subtilis weathers granite; and (2) which granite-forming minerals weather more rapidly via biological processes. Batch system experiments (granite specimen in a 500 ml solution including NaCl, glucose, yeast extract and bacteria B. subtilis at 27 °C) were carried out for 30 days. Granite surfaces were observed by SEM before and after the experiment. B. subtilis had a strong influence on granite weathering by forming pits. There were 2.4 times as many pits and micropores were 2.3 times wider in granite exposed to B. subtilis when compared with bacteria-free samples. B. subtilis appear to preferentially select an optimum place to adhere to the mineral and dissolve essential elements from the mineral to live. Plagioclase was more vulnerable to bacterial weathering than biotite among the granite composing minerals. 相似文献
992.
P. N. Sivalingam D. K. Samadia Dhurendra Singh H. K. Changal Hanif Khan S. K. Sharma 《Genetic Resources and Crop Evolution》2011,58(7):1095-1103
Sixteen germplasm accessions of Prosopis cineraria with suitable horticultural traits were identified from north-western Rajasthan, India, propagated clonally by budding on
seedling rootstock and maintained in the field gene bank. Morphological characterization of seven-year-old trees of these
accessions by 21 traits indicated a lot of variation among the accessions tested. Higher number of flowers per raceme was
found in accession CIAH/K2, higher width of ripened pod in CIAH/K5, higher number of seeds per pod in CIAH/K12 and a higher
weight of seed per pod in CIAH/K6. Overall, CIAH/K16 was found to be a superior genotype for most of the useful traits. High
significant positive correlation was obtained with traits useful for horticultural values. Out of 62 random decamer primers
for random amplification (RAPD) reaction, and four minisatellite core sequence for direct amplification of minisatellite DNA
(DAMD) screened with these accessions, 12 RAPD and 2 DAMD primers were found polymorphic. Average polymorphism resolved by
these markers among the accessions was 93.2%. Genetic diversity revealed by Jaccard’s co-efficient was between 0.11 and 0.77,
and four major clusters were identified among these accessions by phylogenetic analysis using NTSYSpc-2.02e software. This
study shows the existence of high genetic diversity within these accessions. 相似文献
993.
The choice of analytical method and sample pretreatment has significant consequences for the shape of particle‐size distribution (PSD) frequency curves, and therefore for the evaluation of soil textural parameters. Here, the comparison of several granulometric methods based on different physical principles is presented: wet sieving (WS), based on gravity and the mechanical force of water, was combined with pipette (PP) sedimentation/settling velocity, Micromeritics SediGraph (MS) sedimentation/x‐ray attenuation and Coulter Counter (CC) electroresistance particle counting. The Malvern Mastersizer (MM), an instrument based on laser diffraction, was used without WS. Twelve typical temperate‐region soil types were chosen for this study on the basis of their mineral composition, organic matter content, conductivity and magnetic susceptibility. The modalities of PSD frequency curves obtained by different methods were compared. The results showed considerably larger clay‐fraction contents determined with the sedimentation techniques, PP and MS, than that obtained by CC or MM. Statistical correlation and regression models were used to compare the fractions of clay, silt and sand obtained with different methods. Linear correlations were found in almost all cases, except those comparing clay fractions obtained by CC with those obtained by MM, PP and MS methods. These correlations were non‐linear. The observed difference was attributed to the presence of aggregates and/or magnetic properties of soil particles. However, more data are needed to verify this hypothesis. The implications of sample pre‐treatment with dispersant and hydrogen peroxide (H2O2) were evaluated by the MS and CC techniques and observed by the scanning electron microscope. H2O2 was found to be an efficient disaggregating agent. The use of dispersant resulted in the increased amount of the clay fraction measured by the MS method. 相似文献
994.
This paper reports on research into the effectiveness of pineapple monocropping or intercropping systems (with cowpeas or egusi-melon) for reestablishing vegetative cover to check soil erosion on a reclaimed gulley in the tropical rainforest of southeastern Nigeria. High-density pineapple planting, intercropped with egusi-melon, was found to promote rapid vegetative cover, checked soil loss, improved soil structural stability and produced a high crop yield. Soil loss was moderate in pineapple plots intercropped with cowpeas and least in pineapple plots intercropped with egusi-melon. Increasing pineapple density enhanced the field establishment of cowpea and egusi-melon respectively. 相似文献
995.
Chino Mitsuo Moriyama Kiyoshi Saito Hiroshi Morn Tadahiro 《Water, air, and soil pollution》1991,(1):829-837
The amount of heavy metals discharged from daily life was estimated in order to know the origin of the metals contained in the sewage sludge which is produced in the wastewater treatment plant treating only domestic wastewater. The amounts of the metals discharged from our daily life were estimated to be in the range of 0.2 to 0.3 for Cd, 1.6 to 1.9 for Ni, 3.5 to 6.8 for Pb, 0.8 to 1.4 for Cr, 8.2 to 19.3 for Mn 9.4 to 55.8 for Cu, 44.3 to 62.7 for Zn and 111 to 293 for Fe in mg.d–1 per person, Using these data, the cycle of the metals in our daily life was discussed in relation to land application of sewage sludge. 相似文献
996.
J. Shen Q. Zhao H. Tang F. Zhang Z. Feng T. Okita N. Ogura T. Totsuka 《Water, air, and soil pollution》1995,85(3):1299-1304
During the period from 25 May 1991 to 30 May 1992 the atmospheric concentrations and depositions of oxides of sulfur were continuously measured in a suburban masson pine forest which is currently experiencing severe dieback, in Chongqing, China. The annual mean concentrations of SO2 and particulate SO4 2? were 220 μ g/m3 (77 ppbv) and 32 μ g/m3 respectively. The atmospheric concentrations of these sulfur compounds were high in late autumn and winter. The annual wet and dry depositions of sulfur to the forest as measured by throughfall and stemflow were 93.1 and 46.6 kgSha?1a?1 respectively. These depositions are among the highest level ever reported in the world. Althogh the cause of the dieback of the masson pine trees has not been unequivocally determined, it is probable that the direct impact of SO2 is more likely the cause than acid deposition. 相似文献
997.
998.
Changes in soil properties and yield response in relation to tillage and residue management treatments in an irrigated groundnut (Arachis hypogea L.)—wheat (Triticum aestivum, L.) rotation on a sandy soil (1972–1974) and on a sandy loam soil (1974–1976) were evaluated. Tillage treatments (T1 and T2) did not cause significant changes in soil properties. Incorporation of crop residues (5 t residue per ha per crop, T3) caused a substantial increase in organic C, available N, and NaHCO3 -extractable P contents in the top 15 cm of both soils. Residue management treatments (T3, T4 and T5) showed no significant effect on soil bulk density and exchangeable K. Crop yields under no-tillage (T1) and conventional tillage (control, T2) were comparable on sandy soil but on the sandy loam soil, no-tillage yielded significantly lower than conventional tillage. Compared with the control, incorporation of crop residues (T3) caused higher yields on sandy soil for groundnut and wheat by 34.1 and 47.4%, respectively, and on sandy loam by 17.1 and 7.2%, respectively. Mulching with crop residues conserved soil moisture and reduced maximum soil temperature (1.5–5.3°C in groundnut and 1.5–2.9°C in wheat) but other measured soil properties were not significantly affected. Significant yield increase due to residue mulching (T4) was observed in sandy soil but it was significantly less than when total crop residue was incorporated (T3). Increased wheat root-weight density in the top 15 cm soil with residue mulching was not reflected in grain yield. Compared with the incorporation of the total amount of crop residue (T3), incorporation of half the amount and application of the other half as mulch (T5) caused lower yields — on sandy soil for groundnut and wheat by 31.5 and 15.7%, respectively, and on sandy loam by 4.8 and 3.6%, respectively. 相似文献
999.
J N Thompson 《Journal of the Association of Official Analytical Chemists》1986,69(5):727-738
The official methods for measuring vitamin A and carotene in foods and feeds have evolved over several decades. New procedures are needed to permit the use of modern analytical techniques such as liquid chromatography (LC), and to expand the application of official methods to a wide variety of foods. Recent improvements in methodology are reviewed. Emphasis is often placed on the separations achieved by LC, but all factors that affect quantitation, such as sampling, preparation of standards, and protection of the vitamin against oxidation, must be considered in the development of new methods. Many approaches to analysis are possible because of the versatility of LC but not all of them can be used in official methods. Methods for milk, margarine, and feeds can be prepared now for collaborative assays. Although straightforward methods can be developed for the measurement of beta-carotene in certain foods, a full examination of provitamins will probably continue to require a flexible approach and special expertise. 相似文献
1000.
Different concentrations of aqueous extract of fly ash were prepared by soaking air dried fly ash and mixing thoroughly with an electric blender. Extracts were then applied to the seeds of corn (Zea mays L.) and soybean (Glycine max L.) after being filtered through a Whatman No. 42 filter paper. Fly ash extract in the lower concentration range of 0.5 to 1.0% (W/V) had no significant effect on germination and seedling growth of each of the two crops. Higher concentrations of fly ash extracts, however, had deleterious effects on the percentage of germination, viability, number of roots, shoot and root length, fresh weight and dry weight of seedlings of both the crops. The elemental concentrations in shoot and root systems of control seedlings of corn and soybean were found to be the same, whereas in the extract treated corn and soybean seedlings, a relatively high elemental concentration was found in roots as compared to shoots. 相似文献