# Cool Season Lawns: Optimum Ranges



## Kaba (Mar 29, 2019)

I am curious what the actual optimum range for cool season lawns are. My test was completed by waypoint (m3) and showed me bar graphs with where my nutrients stand, but I would to see the actual ppm ranges.

For reference I attached my results from spring.


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## Ridgerunner (May 16, 2017)

Soil science defines "optimal" as that level of a nutrient at which an addition of that nutrient does not result in a positive plant response.

The "optimal range" used by Waypoint and most labs is defined as those levels that have been found to be optimal (see above definition) 75% of the time. In other words any particular level that falls within that range will only have a 1 in 4 chance that an application of that nutrient will result in a positive plant response.

The numbers used to determine that range depend on the data set employed from various studies. Commonly, the data used is from studies of loam soils (CEC @10-15) in general.

You'll need to contact Waypoint to find out what levels (ppm) they used to mark the beginning and end points for their optimal (or any other of the ranges) range for each nutrient.


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## Ridgerunner (May 16, 2017)

Waypoint Fact Sheet:
http://www.waypointanalytical.com/Docs/technicalarticles/howtointerpretasoiltestreport.pdf
They use the 75% guideline for optimal classification. Within that sheed they publish their optimal ranges for potassium based on CEC.
Caveat: some labs play loose with the term "optimal", especially for "homeowner" test reports and classify what soil science would classify as "sufficient" as being optimal. Don't want us stupid homeowners over applying in this era of Eco-friendly/consciousness.


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## Kaba (Mar 29, 2019)

Thank you so much @Ridgerunner I appreciate all of the information! That was a good lesson.

I had emailed back and forth with Waypoint and they had no idea what I was talking about and abruptly told me to call If I had more questions. I wasn't in the mood to make the international long distance call to speak to someone who had no idea about what I was asking about so I thought I would try here!


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## Ridgerunner (May 16, 2017)

If you have the time, read "The Simple Method" in my soil test thread. It's a method being promoted by a number of turf specialists/professionals for determining optimal levels for "your" soil, climate and maintenance methods. It might give you a better understanding of what the concepts are.


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## Ridgerunner (May 16, 2017)

Here you go. This soil report identifies their starting points and end point for their labeled ranges. Notice how the optimum range for Potassium does/doesn't comport with the ranges stated in Waypoint's Fact Sheet. Report labels really aren't of much use.
https://thelawnforum.com/viewtopic.php?f=24&t=11784
Compare to: http://www.waypointanalytical.com/Docs/technicalarticles/howtointerpretasoiltestreport.pdf


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