MLSN is a modern method for interpreting soil tests for turfgrass. This method is designed to do two things.

1. Prevent nutrient deficiencies by recommending nutrients as fertilizer when they won’t be supplied in adequate amounts by the soil.

2. Avoid unnecessary fertilizer applications by identifying soils which can supply enough nutrients to the grass.

The MLSN guidelines were developed in a collaboration between ATC and PACE Turf, with an introduction in 2012. Since then, MLSN has been used with great success by turfgrass managers all over the world.

All the posts tagged MLSN on the ATC website. There are a lot of them. You’ll almost certainly find what you are looking for there.

Use the #MLSN hashtag on Twitter to see relevant posts, ask questions, and share results.

There’s an MLSN Turf Facebook page.

PACE Turf’s MLSN page.

PACE Turf’s climate appraisal form uses temperature and soil test data from your site to predict nutrient use and fertilizer requirements.

How do I know the nutrients from the soil test are available?

You know the nutrients are available because you’ve done a soil test. That’s what a soil test is – by definition it produces a nutrient availability index. If you don’t trust the soil tests, then I suggest skipping them altogether. Instead, assume the soil can supply nothing, and supply to the grass 100% (or a little more) of its possible use of each element. This isn’t the most efficient way to do it, but you won’t need to worry about availability, and it is guaranteed to supply all that the grass can use.

MLSN guideline, target level or minimum level?

Conventional soil test interpretation may give the impression that there are target or optimum levels in the soil. The MLSN guideline is a minimum value – minimum is the M in MLSN so we haven’t always repeated that – that one doesn’t want to drop below. It’s not a level below which one will have deficiency. It’s not a target level that one ideally will have the soil at. What the MLSN guideline represents is a level in the soil with enough of that element to produce high quality turf. There is high quality turf in soils with less of that element too, and that’s why we are confident the MLSN guideline is a safe level. But there aren’t a lot of soils with less, so we suggest keeping the soil from dropping below the MLSN guideline.

Seriously, the same minimum for every grass, soil, and location? No regional customization?

We are confident that the MLSN guideline is enough to produce high quality turf for every grass, everywhere. MLSN has the ultimate customization, however, because the grass use of elements is entirely site specific. In order to ensure the soil doesn’t drop below the MLSN guideline, one has to estimate the expected plant use over time. That’s where the customization comes in.

How is this different than conventional soil test interpretation?

The focus of MLSN is on keeping the soil from dropping below a known safe level. To do this, one must account for how much the grass uses over time. The MLSN approach explicitly calculates the grass use. The conventional interpretation is about classifying as low, medium, or high based on soil nutrient levels.

What about micronutrients?

I don’t worry about them. They are used in tiny amounts by the grass. The grass uses about 400 times ($\frac{40000}{100}$) as much N as it does the most used micronutrient. The grass probably can get all the micronutrients it needs from the soil, because it uses such small quantities of them. And because it uses such small quantities of them, if you are worried about it, apply micronutrients. It doesn’t cost much and is easy to do.

What about salinity?

Salinity can kill the grass. That’s a major problem. To keep the grass from getting killed by high salinity, one needs to leach the salts from the soil. I wouldn’t worry much about soil nutrient levels or MLSN if I have a salinity problem. I would leach the salts, and I would supply 100% or a little more than the grass can use.