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Soil Science Society of America Journal Abstract -

‘A’ Values of Potassium Related to Other Indexes of Soil Potassium Availability


This article in SSSAJ

  1. Vol. 31 No. 3, p. 344-348
    Received: Sept 19, 1966
    Accepted: Jan 11, 1967

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  1. W. F. Nuttall,
  2. B. P. Warkentin and
  3. A. L. Carter2



A technique was developed to measure ‘A’ values of K with oat (Avena sativa) plants grown in the greenhouse and with the radioactive isotope 42K. The isotope 42K has a short half-life (12.42 ± .03 hours) and was applied to the soil as KCl (approximately 2 mc of 42K/g of 39K) 14 to 18 days after seeding. Plants were harvested to determine initial quantities of K at the time of tagged fertilizer application. Six days later the fertilized plants were harvested and the activity in the plant tissue was counted in a liquid scintillation spectrometer. For 11 soils the total of exchangeable K plus nonexchangeable K accounted for 56% of the variability in K uptake at the time of tracer application, whereas 92% of the variability in ‘A’ values was accounted for by these measurements. Results from the experiments indicated that both amounts of exchangeable and nonexchangable K should be used as availability indexes.

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