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Title: Effect of temperature and solvent/soil ratio on the extraction of phosphorus and potassium
Author: Simonis, Asterios D.
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 1973
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Ten extracting solutions were used to study the effects of pH, solvent/soil ratio and temperature on the amounts of P and E extracted from 51 soils, 38 collected from experimental plots in England and Wales and the remainder from Scotland and Greece, representing wide ranges in texture, parent materials and soil characteristics. The amounts of P extracted by 0.5M HOAc and NaOAc mixtures buffered to 5 equidistant steps within the pH range from 4.00 - 5°25 were determined. The data for 31 soils at seven solvent/soil ratios obtained by plotting pH against P extracted, show that the solubility of P falls off strongly as the pH is raised, above pH 4"00o On average, at solvent/soil ratios 3d25 and 200, the P extracted decreased by 36$ and 45$ respectively for each unit rise in pHc No clear pH dependent relation for the K-extraction was obtained. The effects of solvent/soil ratio were studied over the range 3125 to 200. Generally the amounts of P and K extracted increased as the ratio increased. The magnitude of the ratio effect on the P-extracted was generally in the order HOAc > acetate buffer solutions > NaHCO. , being substantially greater in the calcareous soils, except forthe NaHCO. extraction0 Por K-extraction the ratio effect was about the samefor HOAc and acetate buffer solutions, greater for NaHCOj, especially at high ratios, and much smaller for the NH. OAc solution, The replacing ability ofHOAc solution was about 6. of that of NH. OAc at ratio 40, of acetate buffersolutions about 43$ at ratio 5> and that of NaHCO. solution about 65$ at ratio20, but more than 10C$ at ratios > 100. The effect of temperature on the extraction of P with acetate buffer and HOAc solutions was complex and its direction and magnitude depended on the nature of the soil and the solvent/soil ratio. NaHCO. extraction was very sensitive to changes in temperature, increasingby about 3$ per °C risec Temperature effect on the extraction of K by acetate buffer and HOAc solution had the same positive magnitude, about 1--$ per °C increase, but it was generally very small for NH. OAc extraction. The soils were cropped in the greenhouse with ryegrass in two separate experiments with different levels of phosphorus and potassium fertilizers to provide P/K response curves. P and K uptakes and 'P1 and 'K' values equivalent to the a-values as defined by Dean, were used as plant parameters for correlation with chemical methods of assessing soil P and Ko The NaHCO. amethod was leastaffected by soil type and yielded the highest coefficients of correlation. The 'P' and 'K' values appeared promising for evaluating the P and K status of soils in long-term experiments, differentiating between different P and K levels.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available