THE MEASUREMENT AND MECHANISM OF ION DIFFUSION IN SOILS. IX. CHANGES IN SOIL ACIDITY NEAR A SOURCE OF BICARBONATE IONS

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Abstract
Summary: To simulate processes tending to raise the pH of soil near a plant root, a stack of moist HCO‐3saturated ion exchange resin papers was placed in contact with non‐calcareous soil of varying pH, containing HC1 + CaCl2 in the soil solution. Changes in the concentration profiles of Ca2+, Cl‐ and H+ in the soil were followed. HCO‐3 released from the resin in exchange for soil Cl‐ reacted with the soil and raised its pH. Increases of up to 1 unit were measured near the interface. The zone of pH increase extended into the soil much less than the zone of chloride depletion. It was shown that Ca2+ could accumulate near the interface in the absence of mass flow in this experimental system.