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MLSN made easy

I am totally guilty of making the MLSN more complicated than it needs to be. When the MLSN was first developed, it showed me a whole new world in the ways that I could fertilize grass. Naturally, I wanted to test the limits and see what else I could learn. In the process I did some complicated math, calculations and measurements to have fun with this new found knowledge.

The MLSN are not targets, they are soil levels you should not go below and do not include nitrogen recommendations.

Not everyone needs or should do that, however. The MLSN guidelines are actually extremely easy to use and you don't have to do much math if any to get the full benefit of the guidelines. You can make it as easy or difficult as you want.

Micah Woods has talked about it before on his blog but I will share it again with my own take.

If you want to make turfgrass fertilizing as simple as possible. Don't test your soils and simply just apply fertilizer in the ratio that the nutrients are found in the plant. The table below shows this ratio but I can simplify it further.

 N:P:K of 8:1:4


I see lots of granular fertilizer blends with a ratio similar to 30:3:15. That's good and will do you for the macronutrients on your turfgrass. Throw some Dolopril every once in a while for Mg and Ca. You'll need about 5% as much Mg as you apply N and 8% as much Ca. If you Ca is high but you still need Mg, use epsom salts. Apply a micro nutrient containing fertilizer every once in a while but don't make it a big part of your program. Don't worry about it. This method described above is the STERF Precision Fertilisation method. That link is to their updated guide for fertilisation and I highly recommend it.

The nutrient ratio found in this fertilizer is no coincidence

The MLSN allows you to utilize nutrients stored in your soils. If you have excess nutrients, you won't need to apply those nutrients for a few years until they run out. In some cases they might never run out. Either way, you need to test your soils to use the MLSN guidelines because they use the nutrients stored in the soil to make fertilizer recommendations.

There is a ton of complicated math to figure out how to determine how much nutrients you need to have so that you can apply nothing.....or you can just do this.

Test your soils in the same way every year and compare the results for each nutrient. If you do your soil tests with Micah Woods at the Asian Turfgrass Center, he does this for you.


www.asianturfgrass.com

For the macronutrients you can see that there has been virtually no change in phosphorus Over the years. The green line is the average amount in all his samples and the red line is the MLSN. I am above the MLSN guidelines so I should not have any problems with phosphorus deficiencies in my greens. I can keep doing what I am doing for phosphorus applications or slightly reduce them in relation to my nitrogen applications. I have been applying phosphorus in a ratio of 0.12 to nitrogen which is almost exactly the ratio it is found in the plant and you can see that this has no impact on the soil P levels because the plant uses everything I apply as fertilizer.

Potassium saw a big drop in 2022. This was intentional. I was well above the average potassium levels and much higher than the MLSN. In previous years I was applying potassium (K) at a 0.5 ratio to nitrogen and the soil levels were rather stable. In 2022 I applied K at a ratio of 0.16 to nitrogen which is much lower than the levels found in the plant. This resulted in the plants using some of the K in the soil and this caused the soil levels to drop. Our greens are now below average but above the MLSN. We can now resume applying K at a ratio of 0.5 to nitrogen to ensure we do not go below the MLSN guideline. 

The nutrient ratio for macronutrients on my greens next year will be 8:1:4 or the ratio found in the plant. I might only apply P in the summer when growth rates are the highest to keep my shallow rooted poa happy but otherwise it will be pretty simple.

I will take the exact same approach with the other nutrients which is outlined below. I know how much of each nutrient I applied in previous years, and I can adjust them to either drop their soil levels further, or keep them constant.

If you soil test results are trending upward, apply less of that nutrient next year until the soil test levels stabilize or drop to where you are comfortable with them being.


www.asianturfgrass.com

I have only seen soil test results compared like this for the past 3 years and I can now say that this makes fertilizer decisions very easy. No difficult math and no complications. Even if the MLSN is wrong I know that I have good turfgrass today and can keep my nutrients constant in the soil to ensure that I have good turfgrass tomorrow. This can only be done by comparing your results year after year.

If you have been doing soil tests consistently for the past few years, compile them together with yearly averages and see what the trend line looks like. Are your nutrient levels going up, staying the same or going down?




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