Micah Woods
April 29, 2015
3.4k

# MLSN Guidelines: what they are, and how to use them

The presentation explains the MLSN guidelines and answers questions about their development and use. The MLSN guidelines work like this.

1. Keep the soil levels of K, P, Ca, Mg, and S from dropping below the MLSN guideline.

2. Estimate future use of those elements, and make sure that amount can be supplied by the soil, while still keeping the soil above the MLSN guideline.

3. If the soil doesn't have enough to do that, then apply enough of that element as fertilizer to keep the soil above the MLSN guideline.

April 29, 2015

## Transcript

1. MLSN Guidelines
What they are, and how to use them
Micah Woods
Chief Scientist
Asian Turfgrass Center
www.asianturfgrass.com
6 May 2015
a TurfNet webinar

2. MLSN in 10 minutes
MLSN is an acronym for
Minimum Levels for Sustainable Nutrition. This is a method for the
interpretation of soil nutrient analyses.

3. MLSN answers the 2 questions of soil testing
1. Is this element required as fertilizer?
2. If it is required, how much?

4. More specifically…
One can express the quantity of an element required as fertilizer as
Q.
a + b − c = Q
where,
a is the quantity of the element used by the grass
b is the quantity of the element required in the soil
c is the quantity of the element present in the soil
Q is the quantity of the element required as fertilizer

5. MLSN is a value for b
amount needed
a + b −
amount present
c =
fertilizer requirement
Q
a is a site-specific use estimate, b is the MLSN guideline, and c is the
soil test result.

6. a, www.paceturf.org/journal/climate

7. b

8. Using MLSN
1. Keep the soil levels of K, P, Ca, Mg, and S from dropping below
the MLSN guideline.

9. Using MLSN
1. Keep the soil levels of K, P, Ca, Mg, and S from dropping below
the MLSN guideline.
2. Estimate future use of those elements (a), and make sure that
amount can be supplied by the soil, while still keeping the soil
above the MLSN guideline (b).

10. Using MLSN
1. Keep the soil levels of K, P, Ca, Mg, and S from dropping below
the MLSN guideline.
2. Estimate future use of those elements (a), and make sure that
amount can be supplied by the soil, while still keeping the soil
above the MLSN guideline (b).
3. If the soil (c) doesn’t have enough to do that, then apply
enough of that element as fertilizer (Q) to keep the soil above
the MLSN guideline.

11. As an example for K
a + b − c = Q

12. As an example for K
a + b − c = Q
In ppm, a = 100, b = 37, c = 70.

13. As an example for K
a + b − c = Q
In ppm, a = 100, b = 37, c = 70.
amount needed
100 + 37 −
amount present
70 =
fertilizer requirement
67

14. As an example for K
a + b − c = Q
In ppm, a = 100, b = 37, c = 70.
amount needed
100 + 37 −
amount present
70 =
fertilizer requirement
67
Convert between 3-dimensional (ppm) and 2-dimensional (ex. g m-2,
or lb 1000 -2) based on rootzone depth and soil bulk density. For a
10 cm deep rootzone with bulk density of 1.5 g cm-3, 1 g m-2 equals
6.7 ppm, and 1 lb 1000 -2 equals 33.5 ppm. Using that conversion,
Q of 67 ppm is a K requirement of 10 g m-2 or 2 lb 1000 -2.

15. estions?

16. Is there continued field sampling or any plans to be er
regionalize the sampling for possibly di erent MLSN numbers
for di erent regions or possibly between di erent soil types
(ex. USGA vs. Native Soil)?
MLSN is dynamic in that we systematically add data and review the
guidelines. The Global Soil Survey is an ongoing project to gather
more data. No immediate plans for regionalization, basically
because of lack of data, and scope of project. Note, however, that
while b is constant, a is infinitely site-specific and c is both soil and
site-specific.

17. What soil testing method(s) should we utilize to determine
the nutrient levels in the bank prior to making fertilizer
applications to correct deficiencies (if any)?
We used the Mehlich 3 extraction for the development of the MLSN
guidelines.

18. What about the correlation with other testing methods. I have
years of soil test data, but unfortunately these used a di erent
extraction method (I believe ammonium acetate). Is there a
reliable and accurate way to convert the values from other
extraction methods to Melich 3?
There are some conversion equations that can be used. Any
conversion will introduce some error, but with a bit of e ort one can
make useful estimates.

19. Soil paste extracts? yes or no?
No. Soil paste extracts, or saturated paste extracts – these are for
assessing soil salinity. Not a good test for determining how much
fertilizer should be applied.

20. Why not regionalization? WOW‼ I simply CANNOT wrap my
head around the thought of not considering soil types and or
regionalization for nutrient recommendations‼ So are you
saying that sand has the same nutrient holding ability as a
rich sandy loam
I agree that it seems counterintuitive to make nutrient
recommendations with guidelines (b) that admi edly do not
consider soil type or region. But by thinking about the a and c of the
equation used to get Q, there is infinite regionalization. These are
grass species
desired growth rate
site soil conditions
time of year
site climate

21. I’ll ask myself a question. Can you explain how the guidelines
were developed?
Sure. I’ll use potassium (K) as an example.

22. Guideline development process: the raw data
0
100
200
300
400
500
0 1000 2000 3000
3721 soil samples from good turf
K (ppm)

23. Data organized into a histogram
K (ppm)
Frequency
0 100 200 300 400 500
0 100 300

24. Remember, all the samples are from good turf, like this

25. I am curious about the definition of good turf. What are the
characteristics of good turf?
For the MLSN samples, which all come from
professionally-managed turf areas, the good turf is from areas that
the professional turf manager identifies as performing well at the
time the sample was collected. It is the inverse of bad turf or
problem areas identified by a professional turf manager.

26. With an overlay of probability density
K (ppm)
Frequency
0 100 200 300 400 500
0 100 300
density

27. A gaussian (normal) model doesn’t fit well
K (ppm)
Frequency
0 100 200 300 400 500
0 100 300
density
normal

28. A log-logistic distribution fits the data much be er
K (ppm)
Frequency
0 100 200 300 400 500
0 100 300
density
normal
log-logistic

29. Probability of the sample being below x
0 100 200 300 400 500
0.0 0.4 0.8
K (ppm)
Cumulative probability
data

30. Model is very close to the data
0 100 200 300 400 500
0.0 0.4 0.8
K (ppm)
Cumulative probability
data
model

31. Identify a MLSN for K at cumulative probability of 0.1
0 100 200 300 400 500
0.0 0.4 0.8
K (ppm)
Cumulative probability
model

32. Fertilizer is recommended to keep the soil above MLSN
K (ppm)
Frequency
0 100 200 300 400 500
0 100 300

33. Would you elaborate on the potassium trial conducted by
Rutgers where winterkill was more severe on poa plots that
had less than 50 ppm of K?
In the trial at Rutgers, there is a K deficiency in plots not supplied
with K. Where K has been supplied, the winter damage was not
evident, and anthracnose is reduced. If the MLSN approach were
implemented on those trials, enough K would be supplied to
eliminate the deficiency.

34. How do you convert a soil report results from lbs/ acre to ppm
to see if one’s numbers are above or below the MLSN
requirements?
You divide lbs/acre by 2 to get ppm, assuming the samples are from
a 6” (15 cm) depth. You should be ge ing results in ppm which is
what the lab machines measure. Any lb/acre or lb/1000 or kg/ha
reporting is a calculated number from the ppm result.

35. Can I also assume that you also do not consider that some
irrigation water can act as a stripper?
That’s correct. If there are no salts in the water, then there won’t be
anything in the water to exchange with ions in the soil, and it won’t
act as a stripper. And one would not be leaching the soil if the water
doesn’t have salt in it. If the water does have salt in it, then the ions
in the water will exchange with the ions on exchange sites in the
soil, to some extent, with the tendency being more adsorption of
divalent cations (Ca2+, Mg2+) in the soil and more monovalent
cations (K+, Na+) in solution.

36. What are your thoughts on nutrients being tied up in the
soil
This is an unnecessary complication. One measures nutrient
availability by doing a soil test and interpreting the soil test to
determine if a nutrient is required as fertilizer.

37. Was the work done to develop the MLSN done at 4 or 6
inches? Also, what if you have specified to your lab that the
samples were taken at a 4” depth?
The samples for the development of MLSN were from 4 inches (10
cm). The lab should report ppm units back to you, which are
independent of soil depth; if the lab reports lb/acre or kg/ha, they
will have calculated that based on the sample depth you provided
them.

38. Once you are above those levels, you just need to maintain it
to that point? The numbers that I have are well above those
levels, therefore I would not need to apply Ca, P, Mg or K. Just
a straight N product, since the other nutrients are not lacking
in the soil makeup? How does one do that in a natural or
organic program in which many products contain small
amounts of P and K with the N application?
That’s correct. And I would do that as best as I could, trying to use
products with low amounts of P and K. Really I would try to avoid P
completely if the soil had enough.

39. I would like to see info included about soil health testing
...My thoughts are that we as turfgrass managers leave
behind the biological leg of the stool and rely on the physical,
and chemical legs exclusively and that the real MSLN could be
improved upon and may be lowered based on soil health.
Good point. There are some intriguing new tests for assessing soil
biology or “soil health.” But these tests su er from the same
problem as conventional soil chemical guidelines – how can one
interpret the results for turfgrass? With tests of soil health, I’m
optimistic about being able to make recommendations in the future,
but at present it would just be guessing.