Soil testing on the Cornell Turfgrass Show
Is soil testing the answer to all your problems?
Frank Rossi and Carl Schimenti had a discussion on the Cornell Turfgrass Show about soil testing, fertilizer, the Park Grass experiment, weeds, and some good ways to sell fertilizer. Also, that perennially hot topic of silicon. You can watch the episode here.
I was glad to hear their discussion of MLSN. Carl and I have discussed this before—the proper way to use MLSN is not to simply use the MLSN minimum value as a yes or no criterion for whether an element should be applied as fertilizer. The MLSN minimum value is meant to be used in a calculation of how much of an element is required as fertilizer.
The SLAN soil test interpretation ranges for turfgrass are so high, as discussed by Carl and Frank, for a lot of reasons. One of those reasons is no consideration of plant use. The MLSN guidelines were developed in a completely different way, and are not designed to be used in the same way. The MLSN guidelines don’t have a probability of plant response and are not meant to imply a probability of plant response to applied fertilizer.
In plain terms, when you keep the soil at or above the MLSN guideline for an element, you can have a high level of confidence that the grass has access to all of that element that it can use. Basically, you are putting the nutrient management on cruise control, and you don’t have to worry about an element possibly being deficient. But the grass is alive and using nutrients, soil nutrient levels are dynamic, and I always recommend using MLSN with that in mind, rather than taking the way one might interpret a soil test using the SLAN method and substituting in MLSN values. Yes, that works, sort of, but it’s not the way MLSN is meant to be used.
For more about this, here’s a selection of posts that discuss this issue: