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Chesley, Ontario | Whoa!! I think you answered too quick on that one, Ed;
For P, the best test on calcareous soils will be the Olsen. For acid soils, we have found the Olsen to work as well, but the labs would far rather do the Mehlich or Bray, and they do a good job on acid soils but not alkaline. The other factor is what soil test the fertilizer rec's are calibrated for, since you can't just take the numbers from one and use it with a test calibrated for a different test.
Ammonium acetate is used for the cations, and it is not affected much by soil pH.
For zinc and iron, it is a whole different suite of tests. Mehlich, using an ICP in the lab, will measure almost any element, but the numbers don't always mean much. Same with DTPA. The big factor in micronutrient availability in your soils is probably pH.
For the micros, tissue tests might be the best indicator...don't put a lot of weight on the soil test results. | |
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Iron and Zinc in wheat ground
