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| Keith,
Thanks for sorting that out.
As I understand it, the DTPA test eliminates a lot of the need for pH correction during interpretation. A very high pH (the original post did say calcareous soils) will make Zn less available, true, but the test is taking much of that into account (assuming it is DTPA and not HCl).
I agree that soil tests for micronutrients aren't all that solid in their predictive value. But it appears that the DTPA test for Zn is in the ballpark. The problem with much of the soil testing is that we are amalgamating a bunch of cores over a largish area. Hit one area that is higher (old fertilizer spill, manure clump, grain spill, etc) and it skews the whole thing. | |
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Iron and Zinc in wheat ground
