"The salesmen all suggest Calcium"

Jason Chennault and I had a conversation about interpreting soil tests.

I had seen test results for a site and didn’t think there were any problems with the soil. Jason wrote back with more information.

An example is the salesmen all suggest Calcium (and yes I know your thoughts about that 🙂 ) but suggest applying foliar P, noting it won’t be soil applied nor adding to the soil. They suggest that I’m high in S, my Ca and Mg ratios are concerning and on and on. Nothing that persuades me to do one thing or another exactly, just there’s so many interpretations of the sample results.

There are certainly many interpretations of test results, but that doesn’t mean all interpretations are correct. I think it makes sense to interpret soil tests in this way.

  1. Make the assumption that if there is enough of an element, then adding more of that element will have no effect.

  2. Don’t worry about the specific function of each element. Rather, make sure that enough of each element is supplied to the grass.

  3. Then, find out how much is enough.

  4. This can be done by making sure that the amount of an element in the soil stays above the MLSN guideline.

  5. Because the MLSN guidelines have been identified from soils that produce high quality turf, and have a safety margin built in to ensure they are not too low, have confidence that as long as nutrient levels remain above the MLSN guideline, the turf will be supplied with all of that nutrient that it needs.

After going through that process of interpretation (full explanation and examples here), I like to remember this quote from Wayne Kussow: “How many more times do I have to say that applying nutrients to turfgrass growing on soil already well supplied with the nutrients is a waste of time and money?”

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