Bob, did you use the slurry test method yourself and produce inaccurate results? Those hand-held devices aren't for everybody, I know, you have to keep them cleaned, calibrated, and cared for. Maybe that's not your thing.OK slurry test in the field is NOT accurate.
I read the article abstract cited by Tortured Soul. It's not the full article, but it states the conclusion well enough.
In Assessment of hand held ion selective electrode technology for direct measurement of soil chemical properties
J. R. Davenport & J. D. Jabro, https://www.tandfonline.com/doi/abs/10.1081/CSS-120001108, the abstract says in pertinent part (emphasis added by Emeraldo):
"The objective of our study was to determine if these devices could be used to directly measure ion content in soils. Two different soils, a Quincy sand and a Warden silt loam, made into slurries by adding water to achieve 50, 40, 30, 27.5, 25, 22.5, 20, 17.5, or 15% soil water content by volume. The slurries were directly applied to the hand held ISE (Cardy meter) five times for each soil texture and moisture content. In addition, soil solution was also sorbed onto absorbent paper and the paper placed directly on the Cardy meter surface. The results were compared to soil NO3-N, K, Na, and pH determined by conventional methods. The hand held soil pH meter worked exceptionally well on soil slurries and did not fail in making measurements even after over 500 readings."
So a good pH meter can work "exceptionally well on soil slurries" tested in the field, says this study.
I still don't know where you got your information, but I tend to believe a published study by professionals over someone's off-the-cuff comments that are unsubstantiated and seem to fly in the face of well-established information and practices. Like the comment about a +/- 4.0 spread for a slurry pH test in the field -- where did you get that? Like the thing about peat moss (or dead cannabis root, for that matter) being "full of nutrients", what is the basis for that? Like the statement about flushing nutrients from soil not being physically possible when the person so stating admitted not even knowing what flushing was, etc. Credibility becomes an issue after a behavioral pattern seems to suggest either insincerity or a disregard for fact, or both (trolling?). I'm here to exchange GOOD, VALID information and maybe learn something from people who actually know what they are talking about.