Potassium Nutrition in the Northern Great Plains

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Potassium Nutrition in the Northern Great Plains
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Outline Potassium (K) Nutrition in the Northern
Great Plains

• Role of K in crop production
• Soil K and soil test levels
• Crop uptake of K
• K deficiencies
• Crop responses to K
• Chloride (Cl) response
• Fertilizer K

Photo courtesy of Lyle Cowell, SWP
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What Is the Role of Kin Plants?

• K activates enzyme reactions
• K controls water uptake and transpiration
• K influences energy production in photosynthesis
  and respiration
• K supports photosynthate transport
• K fosters nitrate-nitrogen (N) uptake and protein
  synthesis
• K is required for starch synthesis in seeds

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Soil K
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Soil Testing Methodsfor K

• Most soil tests for K are based on either an
  ammonium acetate extraction or a similar
  extraction
• In some regions with low CEC soils, K rates are
  often based on the ratio of K relative to other
  bases, such as Ca and Mg
• Ion exchange membranes which measure the soil
  supply rate of K

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Median Ammonium Acetate Equivalent Soil Test K
Levels, 2005
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Median Ammonium Acetate Equivalent Soil Test K
Levels, 2005
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K Deficient Areas on Canadian Prairies
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Potassium Soil Test Ratingand Recommendations

• Soil test recommendations vary among labs.
  
• Most labs use a set of regional crop response
  data to develop fertilizer recommendations based
  on a K soil test. An example

Wheat K2O recommendations using band
application (Agvise Labs)
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What Are the K Requirements of Crops throughout
the Season?
Photo courtesy of Lyle Cowell
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K Uptake of Wheat Duringthe Growing Season
Jacobsen et al., 1992 (graphic from Korb et al.,
2002)
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Crop Uptake of K

• K uptake in
• Crop Yield/A total crop, lb K2O/A
• Wheat 40 bu 80 (19)
• Canola 35 bu 89 (20)
• Peas 50 bu 150 (39)
• Barley silage 4.5 tons 132
• Alfalfa 3 tons 180

K removed in grain in parenthesis.
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Potassium DeficiencySymptoms in Barley
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Potassium Budget in the Northern Great Plains
Region, 2000-2001
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K Deficiency Symptoms
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K Deficiency Symptoms
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Plant Tissue K Guidelines for Crops An Example
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Crop Responses to K

• While many northern Great Plains soils have
  abundant K, the region also has areas with very
  low soil K
• It is not uncommon to find areas of Saskatchewan
  and Alberta with soils testing 30 to 50 ppm K/A
• Crops respond to K application in these low K
  soils

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Barley Response to Soil K Levels and Fertilizer
K2O
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Barley, Wheat, and Canola Response to K
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K Benefits Crop Growth and Yield Longevity of
Alfalfa Stands

• K increases carbohydrate in the crown roots of
  alfalfa during fall growth to increase
• - Winter hardiness
• - Early spring re-growth

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K Helps Reduce Winterkill in Alfalfa
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Crop Response onHigh K Soils

• Yield increases often occur from potash applied
  on soils not deficient in K. Why?
• K responses as a result of
• - Cold soils in the spring (slow root growth and
  nutrient uptake)
• - Dry soils (droughty conditions reduce K
  diffusion)
• - Field (landscape) variability
• - Cl ion (Cl-) response

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Barley Response to Starter K and Seeding Date
Dubbs, Montana State Univ.
Soil K levels - High
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Crop Response to Added K in High K Soils in
Montana (264 Sites)
Skogley Haby 1981
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Crop Response to Added K in Alberta (548 sites)

• Exch. K Total Responsive Average
• ppm/A sites sites, Resp., cwt/A
• 0 - 50 37 70 6.1
• 51 - 100 132 73 4.8
• 101 - 150 115 55 2.5
• 151 - 200 100 52 2.4
• 201 - 300 99 46 2.7
• 301 - 400 37 43 2.4
• gt 400 28 21 1.9

Lopetinsky 1977
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Frequency Distributionof Soil K on a 220 x 220
ft. Grid at Mundare, AB
Penny et al., 1996
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Chloride---An EssentialPlant Nutrient

• The deficiency of Cl in the soil can account for
  crop responses to KCl application.
• Earliest report of Cl crop response ... table
  salt (NaCl) in mid 1800s
• Recognized as an essential micronutrient since
  the 1950s
• Research in the late 1970s revealed insufficient
  levels in many areas

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Crop Responses to Chloride

• Chloride has been shown to have an effect on
• Root rot and foliar diseases in cereal crops
• Seed weight at harvest, especially barley, by
  extending the grain filling period
• Reducing physiological leaf spot in cereal crops
  on fields where soil Cl is less than 10 lb/A (24
  in. depth)
• Increasing crop yields

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Physiological Leaf Spot on Kestrel Winter Wheat
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Chloride May ImproveCrop Yields

• 200 university trials in KS, MN, MT, ND, SD,
  MB, and SK have evaluated Cl response in wheat
  and barley
• Included non-responsive and high Cl sites
• Significant yield response in 48 of trials
• Average yield response of 5 bu/A

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Yield Boost from Chloride Depends on Wheat Variety
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Fertilizer K Management
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Once in the soil, all fertilizer sources are the
same form as found in the soil (K). This is the
form taken up by plants.
K
K2SO4
KCl
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What Happens to Fertilizer K in the Soil?

• Absorbed by crop in year 1
• 20 to 60 of applied K
• Highest recovery on low K soils
• Slowly available K (future years)
• Bulk of remaining K in most soil types
• Future supply of K

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Fertilizer K Sources

• Source Analysis
• Potassium chloride, KCl 0-0-60 (62)
• Potassium sulfate, K2SO4 0-0-50 - 17
• Potassium nitrate, KNO3 13-0-44
• Potassium-magnesium sulfate,
• K2SO4.2MgSO4 0-0-22-22-11
• Potassium thiosulfate, K2S2O3 0-0-25-17

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Fertilizer K Placement
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Barley Response to KCl Placement and Rate
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Safe Rates of Seed Row K application
(Saskatchewan)

• Seed row application of K2O should not exceed(1
  in. spread, 6 to 7 in. rows)
• Cereals 50 lb K2O/A
• Canola 20 lb K2O/A
• Dry pea 15 lb K2O/A
• Combined P2O5 and K2O in the seed row should also
  not exceed the recommended safe rates for K2O
  alone

Source Saskatchewan Agriculture and Food
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Potassium Does Not Cause Roots to Proliferate

• Split-root experiment
• Percent of the total root system on the side with
  K was the same as that on the side without K
• Effects of K on root growth may not be localized
  as is found with P

Classen and Barber, 1977
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Be Sure and Use Soil Testing to Monitor Soil K
Supplies
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SummaryK Nutrition in the NorthernGreat Plains

• K nutrition is critical to crop production
• Most northern Great Plains soils are high in K,
  allowing for a net removal of soil K each year
• Crops take up as much K as N during growth, with
  only a small proportion removed in grain
• Where deficient, crop response to K is greatest
  for barley, followed by wheat and canola
• Crop responses to muriate of potash (KCl) can be
  a Cl response

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International Plant Nutrition Institute655
Engineering Drive, Suite 110Norcross, GA
30092-2604Phone [phone] Fax
770-448-0439www.ipni.net
Reference 06111