Potassium is heralded as a nutrient critical for turfgrass stress tolerance – heat, cold, traffic, and water stress are all associated with potassium fertility. In this webinar, experts will discuss the role of potassium in plant physiology and cover the basics on understanding soil and tissue test interpretation for plant available potassium. They will also review the relevant scientific research on potassium and explain why many managers may be using potassium incorrectly.
4. • 2nd Most abundant mineral nutrient
• Does not have any structural role
• Important in turgor and water relations,
cofactor for enzymes, “stress” tolerance
Potassium in the Plant
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8. Adam Moeller @AdamMoeller
Mar 16
Rutgers Poa plots with < 50 ppm soil K
much more damaged from freeze injury
compared to those with higher soil K
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9. • Improved Wear Tolerance:
– Shearman and Beard (1973)
• No Effect on Wear Tolerance or Recovery:
– Hawes and Kecker (1977)
– Carrow et al. (1987)
– Carroll and Petrovic (1991)
– Trenholm et al. (2001)
– Hoffman et al. (2010 a and b)
Wear Tolerance?
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12. Drought Tolerance?
• Delayed Wilting:
– Waddington et al., 1978
– Escritt and Legg, 1970 –
took 20 years to show up
– Huang, 2001
• Faster Recovery:
– Schmidt and Breuninger,
1981
– Grady and Dickens, 1997
• No effect:
– DiPaola and Engel, 1976
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15. K & Recovery from
Snow MoldPercentsnowmoldincidence
From Woods et al. 2006
K2O applied – lbs/M
0 3 6 10 13 16 19 0 3 6 10 13 16 19
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16. Percentsnowmoldincidence
0 3 6 10 13 16 19 0 3 6 10 13 16 19
K & Recovery from
Snow Mold
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From Woods et al. 2006
K2O applied – lbs/M
17. Potassium fertilization affects psychrophilic
pathogen susceptibility of annual bluegrass
David R. Moody and Frank S. Rossi
Cornell University
November 1, 2010
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19. Inoculation
0 d 90 d 180 d 208 d 236 d 316 d
Establishment K Treatments ‘Hardening’ ‘Mid-winter’ ‘Early-spring’
Greenhouse Low Temperature Reefer
Inoculation
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21. Grey Snow Mold
Tissue K Content (g kg-1
)
12 14 16 18 20 22 24
50
55
60
65
70
75
80
Mean days to 50% necrosis versus tissue K content
at time of inoculation with T. incarnata
Daysto50%Necrosis(Day50)
r2 = 0.98
Pr > F = 0.0009
n = 5
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22. Pink Snow Mold
Tissue K Content (g kg
-1
)
12 14 16 18 20 22 24
70
72
74
76
78
80
82
84
Mean days to 50% necrosis versus tissue K content
at time of inoculation with M. nivale
Daysto50%Necrosis(Day50)
r2 = 0.69
Pr > F = 0.08
n = 5
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24. K Research at UMASS:
– Gray Snow Mold increased 40% as K rate increased from 1
to 9 lbs/M
Ebdon et al., 2006
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27. 0
2
4
6
8
10
12
14
16
18
20
10 20 30 40
Areaunderdiseaseprogresscurve
Tissue K content (g kg-1)
Critical value = 19.6 g
kg-1
R2 = 0.723
From Charles Schmid, Bruce Clarke, Jim Murphy
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Rutgers Anthracnose Data 2012
28. 0
5
10
15
20
25
30
10 20 30 40
Areaunderdiseaseprogress
curve
Tissue K content (g kg-1)
Critical value = 19.4 g
kg-1
R2 = 0.834
Rutgers Anthracnose Data 2013
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From Charles Schmid, Bruce Clarke, Jim Murphy
29. Soil Test Interpretation
Two main philosophies:
– Sufficiency Level of Available Nutrients (SLAN)
• Feed the Plant
– Base Cation Saturation Ratio (BCSR)
• Feed the Soil
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30. • “Ideal” ratios of the major exchangeable cations
• CEC central to use of BCSR
Base cation saturation ratio
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32. • The “Ideal” Soil
–65 to 85% Ca
–6 to 12% Mg
–2 to 5% K
–Remaining H+, NH4
+
33. Reasons I Dislike the BCSR Approach
1. Ignores differences in nutrient needs among plants
– Genetic aspects
– Ecological aspects
2. Scientific literature does not support the claims
3. Results in inefficient use of resources
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34. #1: BCSR Ignores the Plant
• Different plants prefer different soil pH
• BCSR results in a very narrow range of pH 6.0 – 6.5
• Many turf managers attempt to favor bentgrass over annual bluegrass by
modifying root zone pH
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37. Summary
• Potassium is an essential nutrient that plays varied roles in the
plant
• Research on how to best manage potassium in turfgrass is
evolving
• Evidence for potassium affecting wear tolerance is weak
• Potassium plays an important role in drought tolerance, winter
injury, and disease pressure
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38. Managing Potassium:
• Focus on N: K Ratios and Soil Test Levels
• N: K2O in the plant is about 1.5 : 1
– Apply 1.5 : 1 to maintain soil K levels when soil K is
adequate (according to research-based soil testing
guidelines)
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39. Managing Potassium:
• For bentgrass– follow tissue testing for optimum results
– Keep K above 2% in tissue in summer
– Allow K to drop to 1.5% or lower in fall
• Keep tissue levels above 2% in situations where snow mold
is not a concern.
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40. What Counts When it Comes to
Potassium Source?
Mark Davis, Senior Agronomist
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41. Considerations When
Selecting a K Source
• % K2O
• Other nutrients in the fertilizer
• Dry or liquid
• Salt index
• Particle size
• Uniformity Index
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42. The Right Source
Evaluate nutrient content and associated other nutrients
High chloride may be
injurious to some crops
43. Potassium Fertilizers
and Salt Index
• Salt index provides a relative scale to compare the impact of
fertilizer on soil water
• In cases where fertilizer is concentrated, or on salt sensitive crop,
salt index is critical
Salt Index
Potassium Fertilizers Salt Index Salt Index/unit of K2O
SOP 46.1 0.88
KNO3 69.5 1.216
MOP 116.2 1.936
KMS 43.2 1.96
KTS 64 2.56
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44. Salt Tolerance of
Common Turf Grasses
Salt Impacts
• Water imbalance in the Plant,
creating physiological drought
• Ion imbalance, increase energy
consumption to maintain
metabolic process
• Toxicity from specific ions,
Sodium, Chloride and Boron
• Salt impacts plant growth,
stunting, darker green leaf color,
leaf burn and reduced yields
Grass
*Rating
Bermudagrass T
Zoysiagrass MT
Creeping bentgrass MS
Perennial ryegrass MT
Rough bluegrass S
Tall fescue MT
Kentucky bluegrass S
Annual bluegrass S
*T=tolerant, S=sensitive, M=moderately
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45. Particle Size
• Particle size is defined by the size guide number (SGN) value. The
SGN is determined by calculating the average particle size of the
product granules in millimeters and multiplying by 100.
– Materials and products used on turfgrass generally have an SGN
range of 75 to 350.
– Greens products range from 75 to 100,
– close cut turf from 125 to 150 and higher
– cut turf like lawns 150-240.
– SGN is important for fertilizer efficacy because it reflects the
number of particles applied per square inch. Estimated particles
per square inch for SGN values of 100, 150, 200, and 240 are
14-16, 8-10, 6-8, and 4-6, respectively
• Make sure your potassium source is sized to the right
application and the other fertilizers in the blend
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46. Uniformity Index (UI)
• Uniformity Index (UI) is a value representing the relative particle
size variation of the granules within a product.
– A UI of 50 means that the ratio of the smallest particles is one-
half the size of the largest particles. A UI of 100 means that all of
the particles within the product are equal in size.
– UI values range from 35 to 60 and a value of 50 is considered
acceptable for good uniformity of spread.
– UI is important because with rotary spreader equipment larger
granules travel a greater distance than do finer granules.
– A low UI value increases the likelihood of a poor uniformity of
spread.
• Make sure your potassium source has a high UI to ensure good
spreadability
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47. Key Facts About
CMP’s Protassium+
• CMP is the only North American
producer of sulfate of potash.
• Our SOP from the Great Salt Lake is
all-natural, produced in OMRI
approved organic and non-organic
forms.
• Our SOP is virtually chloride free
which enhances quality and yield for
chloride sensitive crops.
• SOP is a unique dual nutrient,
containing both 50% Potassium
(K2O) and 17% Sulfur (S).
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48. Protassium+ (0-0-50-17S)
• High K2O analysis 50%
– Cost benefits per unit of nutrients
• High S 17%
– Sulfur in the sulfate form, immediate plant available form
• Low Cl less than 1%
– Balanced plant nutrition total 67% potassium and sulfur
everything you need and nothing you don’t
• Low salt index
– Flexibility in application and timing
– Safety for the plant and soil systems
• pH neutral
– Will not change soil pH or require liming materials over time
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49. Turf Protassium+ Product
Turf Granular
Suitable for blends used by the turf and ornamental markets. Ideal for
roughs and fairways Typical SGN 220/UI 58.
Turf Blend Greens-Grade
SOP Turf Blend™ GREENS-GRADE is best used for micro-sized blends or
direct applications on short cut golf greens. Typical SGN 90/UI 59.
Turf Blend Mini-Granular
Ideally suited for mini-size turf blends. Mini-Granular has the highest uniformity
index of all the granular SOP's. Mini-Granular can be used on fairways and tees.
Typical SGN 140/UI 66.
Soluble Fines
Fine screened for rapid dissolution in making liquid fertilizer solutions and
suspensions.
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