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Little River, TX | I sent off my collection of soil samples yesterday, & E-Mailed the long suffering contact at Midwest Labs.
I mentioned your soil test results. His response was designed not to chunk rocks at the competition, but his observations were still interesting.
A&L Memphis analysis will typically yield a much higher level of calcium since their method makes the Ca more soluble.
No mention of the more standard K & Mg values.
The hitch is not all clays are the same. The clay I have traps potassium molecules between clay plantlet. The drying process with the shrink swell releases the K & Mg into the available pool. Something that does not happen as dramaticly in the wild.
The key is no soil test is fully useful if there has not been an on the ground validation of test results, fertilizer application, and crop response. That is essentially what I am doing on my farm. That is not something that has been attempted by any of the soils Labs. I have only had one lab tell me they did not want to make recommendations for my soil. Most recommendations are for a standard statistical soil not the soil in question.
Most Labs will have a 10% variability running the same sample through on succeeding days.
Most soil's will have a 30% variability between site locations. This is why they want so much dirt in the sample, to average out the variability.
On these pages currently is a discussion on proper soil probing to minimize sampling error.
Most times all these errors and variability average out, but they can also multiply and produce some rather wild data. A computed CEC is from a magic equation using possibly flawed data. That is the reason why some time ago I started paying for a measured CEC. The cost for this used to be $17.10 but will be $40 the next time I send in samples to be tested for measured CEC.
All the above is why I am so fond of plant analysis. It has some warts, but is still more reliable than soil testing.
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Need some help on my soil test.......South Central Texas
