Base saturation studies of some Vancouver Island soils, and a method for estimating lime requirement

Brown’s Method was found to be a very satisfactory technique for determining the exchange capacity of soils. It was simple, rapid and gave comparable results with Shollenberger’s technique for thirty soils from Vancouver Island. The Puri Method gave comparable results to Brown’s but was too lengthy. Considerable variation occurred at high percent base saturation levels when determined by Schollenberger, Brown and Purl Methods for these soils. It was concluded, however, that Brown’s Method as well as being rapid and simple gave satisfactory results. As much as twenty percent variation in percent base saturation was noted for soils having the same pH value. The percent base saturation of a soil cannot be estimated from its pH with a high degree of accuracy. The total titration curves produced by adding increments of calcium to hydrogen saturated soils showed that the exchange capacity and base saturation could be determined by this method. It was also concluded the position and shape of the curves, indicated the buffer capacity of the soil. In a greenhouse experiment where Virginian Stock was grown as the indicator crop on five levels of percent base and calcium saturation, the following conclusions were made: (1) That a relationship exists between calcium and base saturation of the soil and plant growth. (2) That the flex point for the growth saturation curves occurred at 30% calcium saturation and 60% base saturation for both soil types. (3) That response to lime in the greenhouse coincided with known response in the field. (4) That a relationship exists between base saturation in the soil and calcium content of the plant. (5) That 1200 gm. samples of soil were better suited for saturation studies than 300 gm. samples. (6) That below a certain percent base saturation calcium is not available to plants. (7) That base saturation studies should form a sound basis for estimating the lime requirement of soils. The lime requirement of six soil types was estimated by three methods: (1) Percent Base Saturation expressed on a Volume Weight Basis. (2) Percent Base Saturation expressed on a weight basis. (3) Titration Curves on a weight basis. It was concluded that the Percent Base Saturation Method expressed on a volume weight basis gave a good indication of the lime requirement for the six soil types studied. The latter two methods indicated that very large quantities of lime were required for soils with low apparent specific gravities. This may result in overliming of the surface horizons

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