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Phosphate sorption in soil is controlled largely by Fe-oxihydroxides, and so important changes in P dynamics are expected when the redox potential is modified. Such changes in P sorption when acid soil is flooded, as for rice cultivation, have been evaluated. Samples from an acid sulphate soil in the Mekong Delta of Vietnam were flooded for up to 56 d at 20°C and 30°C. Some of the samples incubated at 30°C were dried in open air for 30 d after flooding. Small redox potential (Eh<0) and pH>6 were rapidly reached in soil flooded at 30°C; less drastic reducing conditions (Eh ?0.2 V) and pH 4–5 occurred at 20°C. Phosphate sorption increased during flooding. The increase was twofold at 20°C, and 10-fold at 30°C. Phosphate sorption index decreased in the soil that was air dried after flooding at 30°C, but still remained two to three times greater than before flooding. These results were compared to the changes in oxalate-extractable Fe, i.e. poorly crystalline or amorphous Fe-oxihydroxides. The increase of P sorption per unit increase of oxalate-Fe was seven to eight fold larger at 30°C than at 20°C. 相似文献
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Phosphorus sorption in soils of the Mekong Delta (Vietnam) as described by the binary Langmuir equation 总被引：1，自引：0，他引：1
VO DINH QUANG VU CAO THAI TRAN THI TUONG LINH J.E. DUFEY 《European Journal of Soil Science》1996,47(1):113-123
Phosphate adsorption isotherms were determined for 20, mostly very acidic, soils from the Mekong Delta. The experimental data were well described by a binary Langmuir equation which considers two groups of sorption sites that differ in their P bonding energies. The maximum P-sorption capacities of these sites were related to the soil properties by simple linear correlation and by stepwise multiple regression. Results suggest that high energy sites are on Al-oxihydroxides or small Al-substituted Fe-oxides and, to a lesser extent, on poorly ordered Fe-oxihydroxides. On the other hand, the P-sorption capacity of low energy sites is mainly related to clay content, and it increases as pH decreases. These sites are also positively correlated with organic carbon and poorly crystalline Fe-oxihydroxides. However, as these two variables are closely correlated with each other, organic matter is likely to be considered as an indirect factor of P fixation through its association with Fe-oxihydroxides and not as an important source of P-sorption sites. The maximum sorption capacity, i.e. the sum of sorption capacities of the two groups of sites, is well described (r2= 0.88) by an equation that takes into account the four variables identified above: Al-bearing oxihydroxides, poorly ordered Fe-oxihydroxides, clay content and pH. Grouping the soils according to the orders of Soil Taxonomy, the P-sorption capacity increases in the following sequence: ultisols < entisols < inceptisols. A P concentration often considered adequate for plant nutrition is 0.2 mg P 1?1 solution, and only the high energy sites are involved in sorption at that concentration. Thus an equation including only Al- and Fe-oxihydroxides could be used to fix P norms in these soils. 相似文献
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D. T. VO W H. HSU E. A. ABU‐BASHA R. J. MARTIN 《Journal of veterinary pharmacology and therapeutics》2010,33(4):315-322
Vo, D. T., Hsu, W. H., Abu‐Basha, E. A., Martin, R. J. Insect nicotinic acetylcholine receptor agonists as flea adulticides in small animals. J. vet. Pharmacol. Therap. doi: 10.1111/j.1365‐2885.2010.01160.x. Fleas are significant ectoparasites of small animals. They can be a severe irritant to animals and serve as a vector for a number of infectious diseases. In this article, we discuss the pharmacological characteristics of four insect nicotinic acetylcholine receptor (nAChR) agonists used as flea adulticides in dogs and cats, which include three neonicotinoids (imidacloprid, nitenpyram, and dinotefuran) and a macrocyclic lactone (spinosad). Insect nAChR agonists are one of the most important classes of insecticides, which are used to control sucking insects on both plants and animals. These novel compounds provide a new approach for practitioners to safely and effectively eliminate adult fleas. 相似文献
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Ajadi RA Adetunji A Omoerah VO Okoh JU 《Journal of the South African Veterinary Association》2006,77(4):202-204
Three series of trials involving 10 domestic short-haired cats were carried out to determine the influence of dosage of contrast media or type of chemical restraint on feline excretory urography. The 1st series (group A) involved 5 cats sedated with 2.0 mg/kg intramuscular (i.m) injection of 2% xylazine and receiving 800 mg/kg of 76 % meglumine diatrizoate (urografin). The 2nd series (group B) involved another 5 cats sedated with 2.0 mg/kg (i.m) injection of 2% xylazine and receiving 1200 mg/kg of 76% urografin. The 3rd series (group C) involved the repeat urography of the group B cats but sedated with 15 mg/kg (i.m) injection of 5% ketamine hydrochloride. Ventrodorsal radiographs were obtained immediately, 5, 15 and 40 minutes after the injection of 76% urografin. Scores were assigned to nephrographic opacification as described in the literature. The heart rates, respiratory rates and rectal temperatures of the cats were also determined before sedation, after sedation, immediately after the injection of 76% urografin and at 15-minute intervals over a period of 60 minutes. In this study, there were significant differences (P < 0.05) in the nephrographic opacification scores between the group A and group B cats at times 0 and 40 minutes post-administration of urografin. Group A cats had good initial nephrographic opacification which faded later while the nephrographic opacification of group B cats progressively increased. Similarly, nephrographic opacification was significantly (P < 0.05) higher in the xylazine-sedated cats (groups A and B) than the ketamine-sedated cats (group C). However, there were no significant differences (P > 0.05) in heart rates, respiratory rates and rectal temperatures between the 3 groups of cats. It was therefore concluded that increasing the dosage of urografin above 800 mg/kg in cats does not provide additional beneficial effects on the nephrograms produced. Xylazine sedation was observed to produce better nephrographic opacification, however, with delayed nephrographic fading compared to ketamine sedation. 相似文献
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