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Using and understanding the MLSN
guidelines for nutrient recommendations
Micah Woods
January 23, 2018
Chief Scientist
Asian Turfgrass Center
www.asianturfgrass.com
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Today’s schedule
09:25 – 11:25: all about MLSN
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MLSN1 is a method for soil test interpretation.
1An initialism for minimum levels for sustainable nutrition.
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MLSN is designed to prevent nutrient deficiencies based on
an analysis of the nutrients in the soil and the expected grass
use of nutrients.
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MLSN newsletter:
www.subscribepage.com/mlsn
ATC newsletter:
www.subscribepage.com/atcupdate
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The key concepts
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Nutrient deficiencies are avoidable disasters.
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The two possible extremes
1. Supply nothing and assume the soil can provide all the
grass requires.
2. Supply 100% (or more) of the nutrients the grass can use.2
2This approach makes the implicit assumption that the soil cannot supply the nutrients.
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“How many more times do I have to say that applying
nutrients to turfgrass growing on soil already well
supplied with the nutrients is a waste of time and
money?”
Wayne Kussow in “Manipulating Creeping Bentgrass Nutrition”
(1995)
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Two questions
1. Is this element required as fertilizer?
2. If it is required, how much should I apply?
To answer those questions, we need to know how much is
used by the grass and how much can be supplied by the soil.
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MLSN is a method for soil test
interpretation
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a, b, and c
• a is a site-specific estimate of plant use.
• b is the amount we want to ensure remains in the soil
after the plant use is accounted for. This is a minimum we
don’t want to drop below. You can think of it as a reserve
amount in the soil. This is the MLSN guideline level.
• c is the amount actually present in the soil. This is the
soil test result.
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a, site-specific estimate of plant
use
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Growth = nutrient use
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Not like this
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Law of the minimum?
“In terms of Liebig’s Law of the Minimum, nitrogen is
usually the element in shortest supply, and therefore
applying nitrogenous fertilizers has a large impact
on plant growth. The reason that nitrogen, of all the
elements, is so often limiting to growth is simply that
plants require a great deal of it.”
Jonathan Silvertown in Demons in Eden: The Paradox of Plant
Diversity (2005)
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3 ways to get a number for growth
1. Estimate from clippings.
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3 ways to get a number for growth
1. Estimate from clippings.
2. Estimate from N applied.
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3 ways to get a number for growth
1. Estimate from clippings.
2. Estimate from N applied.
3. Estimate from temperature.
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b, amount to ensure remains in
the soil
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1. The conventional way – low, medium, & high classification
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1. The conventional way – low, medium, & high classification
2. Conventional guidelines are broken
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1. The conventional way – low, medium, & high classification
2. Conventional guidelines are broken
3. The MLSN guidelines address these problems
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The conventional way – low,
medium, & high classification
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The conventional way
GCSAA GCM Magazine, January 2004
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List of ranges
• low
• medium
• high
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“Low range: a high probability (80-100%)
that applying the nutrient will elicit a
growth response.”
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“Medium range: approximately a 50%
chance of getting a plant growth response
…; if supplemental fertilizer is not applied,
growth will probably be limited, especially
as the season progresses.”
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“High range: little or no crop response is
expected from applying the particular
nutrient.”
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Conventional guidelines are
broken
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“In some cases, turfgrasses have been placed in a
‘high’ P and K requirement category, while pasture
grasses were in a ‘low’ category. This decision was
based on economics, not agronomics. The cost of
fertilization was not considered of primary
importance for turf.”
Carrow, Waddington, and Rieke in Turfgrass Soil Fertility and
Chemical Problems (2001)
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And grass is often grown in sand
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“Unfortunately, turfgrass recommendations appear to
be based on research done with other crops, such as
forages, results from turfgrass fertility studies not
designed to relate to soil testing, and the best
judgement of the agronomist making the
recommendations.”
Turner & Waddington in “Survey of soil testing programs for
turfgrasses” (1978)
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“Numerous turfgrass fertility studies … either did not
take into account intitial soil fertility levels, or were
conducted on only one level of initial fertility.”
Turner & Waddington in “Survey of soil testing programs for
turfgrasses” (1978)
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“Every time a researcher conducts one of these
studies, they tend to find that the levels required are
lower than what we previously thought – meaning
that ‘low potassium’ you got on your last soil test
report might be optimum down the road.”
Doug Soldat in “How reliable is soil testing?” (2013)
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The MLSN guidelines address
these problems
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“I recommend you compare your results with PACE
Turf’s Minimum Levels for Sustainable Nutrition
[MLSN] guidelines ... the minimum levels published
by PACE are drastically lower than many traditional
soil test interpretations, and likely more accurate.”
Doug Soldat in “How reliable is soil testing?” (2013)
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The MLSN guidelines address these problems
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c, the amount actually in the soil
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Using MLSN
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Let’s make sure we have enough beer
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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 kept in the soil
c is the quantity of the element present in the soil
Q is the quantity of the element required as fertilizer
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3 common questions
1. MLSN is a target level, or minimum level?
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3 common questions
1. MLSN is a target level, or minimum level?
2. Same minimum for every grass, soil, and location?
Customization?
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3 common questions
1. MLSN is a target level, or minimum level?
2. Same minimum for every grass, soil, and location?
Customization?
3. How do I know the nutrients are available?
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For more, please see
www.asianturfgrass.com or
@asianturfgrass on Twitter.