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Potassium Exchange Equilibria and Yield Responses of Oats, Barley, and Corn on Selected Quebec Soils¹

ABSTRACT

Potassium:calcium + magnesium activity ratios were used to calculate availability indices on eight Quebec soils. These were compared to available potassium measurements and related to yield responses of oats (Avena sativa L.), barley (Hordeum vulgare L.), and corn (Zea mays L.) to potassium fertilizers in field experiments. Crop growth did not change the potential buffering capacities (PBC^K) of two selected soils, which indicated that the quantity-intensity relation regulated the release of potassium although the activity ratio was greatly reduced. The potassium potential was obtained by multiplying the total amount of exchangeable potassium (–K°) with the potential buffering capacity to place soils on a comparative basis. The potassium potential fully defined the quantity-intensity relation and correlated more closely to crop responses than the activity ratio measurement, the PBC^K, or the available potassium determination.

¹ Part of a thesis submitted by the senior author to the Faculty of Graduate Studies and Research, McGill Univ., in partial fulfillment of the requirements for the M. S. Degree. Supported in part by the Quebec Agr. Res. Counc.

² Formerly Graduate Student, now Research Officer, Canada Dep. of Agr., Melfort, Saskatchewan, Canada, and Assoc. Professor, Dep. of Soil Sci., Macdonald College of McGill Univ.

Received for publication March 20, 1967. Accepted for publication September 6, 1967.