The MLSN guidelines have been updated for the first time since their release in 2012.
Compared to the previous version of the guidelines, the new MLSN guidelines for potassium and phosphorus are higher, and the new guidelines for calcium, magnesium, and sulfur are lower.
Why did the guidelines change? Because the design of this project includes regular updating of the guidelines as new data are added. These guidelines are not static. They are designed to be updated to provide the most accurate assessment of soil nutrient levels, based on the way turfgrass is managed today. The current version of the MLSN guidelines includes data from soil test results in the PACE Turf, ATC, and Global Soil Survey datasets.
For more detail, see: