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Amounts of phosphorus taken up by maize plants during 23 days from an Entisol, two Alfisols and an Ultisol from Nigeria, each with three histories of management, were related to the concentration of soil phosphorus extracted in 0.01 m CaCl2; but the relationships differed between kinds of management. Phosphorus in plants 51 days old was not related to concentration. Relationships of plant phosphorus with isotopically exchangeable phosphorus, and with phosphorus extracted from the soils by anion exchange resin, were poor in young plants but were good in the older plants, irrespective of field management. Amounts of phosphorus in the older plants were also well related to estimates of exchangeable phosphorus computed from P in solution and amounts of amorphous iron oxides extracted by ammonium oxalate from the soils, using equations derived in an earlier investigation with a larger group of soils. Thus estimates of exchangeable phosphorus made from simple measurements of the soil constituents that largely control it, and from extraction by resins, are potentially useful to indicate the ability of soils to supply phosphate to crops, and hence to guide fertilizer policies. 相似文献
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Abstract— A general discussion on improvements to veterinary premises covering planning, estimates, legal requirements, layout and costs.
Résumé— Une discussion générale sue l'amélioration des locaux vétérinaires concernant les plans, les devis, les conditions légales requises, la disposition et les frais.
Zusammenfassung— Eine allgemeine Besprechung über Verbesserungen in tierärztlichen Räumlechkeiten hinsichtlich der Grundrissanglage, der Kostenanschläge, der gesetzlichen Vorschriften, der Einrichtung und Kosten. 相似文献
Résumé— Une discussion générale sue l'amélioration des locaux vétérinaires concernant les plans, les devis, les conditions légales requises, la disposition et les frais.
Zusammenfassung— Eine allgemeine Besprechung über Verbesserungen in tierärztlichen Räumlechkeiten hinsichtlich der Grundrissanglage, der Kostenanschläge, der gesetzlichen Vorschriften, der Einrichtung und Kosten. 相似文献
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The effects of lime on adsorption and desorption of phosphate in five Colombian soils 总被引：1，自引：0，他引：1
The effects of lime (applied in the field) on the amounts of total and isotopically-exchange-able phosphate adsorbed from solutions were measured in five soils. The total amount of phosphate adsorbed without lime was in the range 200 to 1700 μg P per g of soil at 0.05 μg P cm−3 of solution. Lime diminished the amount of phosphate adsorbed at all concentrations of solution in an oxisol and a dystropept; in an ultisol and another dystropept, lime tended to increase sorption at small concentrations and diminish it at large concentrations; in a dystrandept that contained spheroidal allophane and a great deal of organic matter, lime increased adsorption at all concentrations up to 1 μg P cm−3 . Lime increased the proportion of added phosphate that was isotopically exchangeable in the oxisol and one dystropept, had no effect in the other dystropept, and diminished the proportion in the ultisol and dystrandept.
Adsorbed phosphate was subsequently desorbed by suspending the soils in solutions without phosphate. After desorption the quantity of exchangeable phosphate in all soils was closely correlated with aluminium extracted by ammonium oxalate; buffer power was correlated in all except the dystrandept, in which it was larger per unit of aluminium than in the other soils; possibly the cause was aluminium associated with organic matter. In all soils lime diminished buffer power allowing a specific amount of exchangeable phosphate to maintain a larger concentration in solution. The beneficial effects of lime on exchangeable phosphate after desorption were consistent among soils, despite inconsistent results when the phosphate was adsorbed. 相似文献
Adsorbed phosphate was subsequently desorbed by suspending the soils in solutions without phosphate. After desorption the quantity of exchangeable phosphate in all soils was closely correlated with aluminium extracted by ammonium oxalate; buffer power was correlated in all except the dystrandept, in which it was larger per unit of aluminium than in the other soils; possibly the cause was aluminium associated with organic matter. In all soils lime diminished buffer power allowing a specific amount of exchangeable phosphate to maintain a larger concentration in solution. The beneficial effects of lime on exchangeable phosphate after desorption were consistent among soils, despite inconsistent results when the phosphate was adsorbed. 相似文献
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High gradient magnetic separation of some soil clays from Nigeria, Brazil and Colombia. 总被引：2，自引：0，他引：2
High gradient magnetic separation was used to fractionate the clay from some tropical soils. Acid-oxalate-extractable iron (Feox) and aluminium (Alox) and total carbon were measured in the whole clay, the magnetic fraction and the tailings. The magnetic separation resulted in a wider range of concentrations of these elements than in the whole clays. In each of the clays Feox was greater in the magnetic fraction than in the tailings; Alox was more variable. Carbon was also concentrated in the magnetic fraction suggesting that it is associated more with Feox than Alox. The relationships between Feox, Alox and carbon depend on soil classification and soil age. 相似文献
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