‘A’ Values of Potassium Related to Other Indexes of Soil Potassium Availability
- W. F. Nuttall,
- B. P. Warkentin and
- 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.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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