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Little River, TX | With the clay soils we enjoy to realize a uniform result the sample must be ground to a powder and highly mixed.
Even then there is a consistent variability of roughly 10% when the samples are run at the same lab.
With my 8 pH soil I request the Olsen chemistry from the lab. I have found that even though they are supposedly using the same chemistry there will be a 20% or 30% difference between most labs.
Testing for K I have found all the labs to be fairly consistent. The same for pH.
Looking at Calcium I have seen some very wild differences, between labs.
The real consistency with labs is each will insist theirs is the best most accurate methods.
The secret is to find what the normal levels reported by you favorite lab, calibrate it to your land, climate, and management. Then stay with them. The key for this is if they will respond to your questions and observations. Midwest Labs are not real enthused as to how I look at some of their results. I do funny things that work, but do not fit the usual text book examples. They can be found in a text or paper but are not considered usual.
In my life I did the home testing bit, changed to the TAMU soils Lab, went back to the home testing, and again back to TAMU. Then I changed to A & L Plains, who would use the Olsen chemistry and reported a CEC value. They stopped communicating and I changed to Midwest. It was then that I started using a measured CEC value rather than a computed CEC value.
I would never use a soils test recommendation, unless that lab had run response trials on your soils. For Sure!
Edited by Hay Wilson in TX 9/26/2006 20:04
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Soil Testing Labs
