Potassium Nutrition in the Northern Great Plains

Photo courtesy of Lyle Cowell, SWP

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

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

Soil WaterK+

K+K+

K+

K+ K+ K+K+

K+ K+ K+K+Trapped K

K

K K

KSoil Minerals

(feldspar, mica)

Soil Colloid

Soil Colloid

Soil Colloid

K

Unavailable (90 to 98%)

Slowly available (1 to 10%)

Readily available (0.1 to 2%)

Soil K

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

Median Ammonium Acetate Equivalent Soil Test K Levels, 2005

Median Ammonium Acetate Equivalent Soil Test K Levels, 2005

2005

ND

SK MBAB

MT

207

259 265

201 254

North American-wide154 ppm

K Deficient Areas on Canadian Prairies

May be deficient in K

May need K for irrigated crops

Potassium Soil Test Ratingand Recommendations

Yield Soil test K, ppm

bu/A 0-40 41-80 81-120 121-160 161-200 201-250 251-750 +750

Fertilizer K recommendation, lb K2O/A

30 35 30 20 10 10 10 10 0

40 50 40 30 15 10 10 10 0

50 65 50 35 20 10 10 10 0

60 75 60 40 25 10 10 10 0

70 90 70 50 30 10 10 10 0

Wheat K2O recommendations using band application (Agvise Labs)

- 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:

What Are the K Requirements of Crops throughout the Season?

Photo courtesy of Lyle Cowell

K Uptake of Wheat Duringthe Growing Season

Jacobsen et al., 1992 (graphic from Korb et al., 2002)

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.

Potassium DeficiencySymptoms in Barley

11

38

49

58

0 60 120 2400

10

20

30

40

50

60

Ba

rle

y g

rain

yie

ld, b

u/A

K2O rate in lb/A

Potassium Budget in the Northern Great Plains Region, 2000-2001

-544-5571352609North Dakota

-301-310942352Montana

-195-2404592332Manitoba

-538-5814359640Saskatchewan

-343-479136128607Alberta

--------------------- K2O, million lb ---------------------

F+M-RF-R(M)(F)(R)

BalanceRecoverable Manure

Fertilizer Applied

Crop Removal

State or Province

K Deficiency Symptoms

K Deficiency Symptoms

Plant Tissue K Guidelines for Crops … An Example

3.9 – 4.72.5 – 3.81.8 – 2.4<1.7Alfalfa – top 6 in.

3.1 – 9.91.6 – 3.01.3 – 1.5<1.2Wheat – heading

2.5 – 3.52.0 – 2.41.5 – 1.9<1.4Wheat – boot

3.1 – 9.91.6 – 3.01.3 – 1.5<1.2Wheat – tillering

HighSufficientLowDeficientCrop type -- stage

% K in plant tissue

Agvise Labs

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

Barley Response to Soil K Levels and Fertilizer K2O

N and P added to soil test recommendation D. Walker, Lacombe, AB

Soil K 50-75 ppm/A

Soil K 75-100 ppm/A

Soil K 25-50 ppm/A

0

10

20

30

40

50

60

70

80

0 12 24

Added K, lbs K2O/A added to seed row

% G

rain

Yie

ld In

cre

as

e

Barley, Wheat, and Canola Response to K

N and P added to soil test recommendation Henry and Halstead, 1968

72 ppm K/A

33 ppm K/A

30 ppm K/A

50 ppm K/A

36 ppm K/A

Canola

Wheat

Barley

0

10

20

30

40

50

60

70

0 100 200 400

Added K (lb K 2O/A Broadcast + Incorp)

Gra

in y

ield

, bu

/A

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

Manitoba - Soil K 116 ppm/A (0 to 6 in.)

100 lb K2O/yrNo K100

Year 1 Year 2 Year 3 Year 4 Year 5 Year 6 Year 70

20

40

60

80

Sta

nd

den

sity

, %

Plant counts in May as % of those the previous September

K Helps Reduce Winterkill in Alfalfa

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

Barley Response to Starter K and Seeding Date

Dubbs, Montana State Univ.Soil K levels - High

April 6 May 6 June 3

7 bu

6 bu

3 bu

0

10

20

30

40

50

60

Ba

rle

y Y

ield

(b

u/A

)

Check

20 K2O

Crop Response to Added K in High K Soils in Montana (264 Sites)

36 Expts.

48 Expts.

33 Expts

97 Expts.

0 20 40 60 80

Winter Wheat

Spring Wheat

Feed Barley

Malt Barley (irr.)

Alfalfa

Corn Silage

Potatoes (irr.)

10 Expts.

22 Expts.

18 Expts.

5.5 bu/A

4.8 bu/A

3.9 bu/A

9.2 bu/A

0.35 t/A

2.8 t/A

25 cwt/A

Frequency of response, %

Each crop represents 2 to 8 cropping yearsSoils testing > 600 ppm (1967-1979)

Skogley & Haby 1981

Barley, oats, and rape – 1968-74

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 6.151 - 100 132 73 4.8

101 - 150 115 55 2.5151 - 200 100 52 2.4201 - 300 99 46 2.7301 - 400 37 43 2.4

> 400 28 21 1.9

Lopetinsky 1977

Frequency Distributionof Soil K on a 220 x 220 ft. Grid at Mundare, AB

Penny et al., 1996

Mean = 135 ppm

Mode = 108 ppm

0

5

10

15

20

25

30

35

Fre

qu

en

cy

(%

)

59-101 101-143

143-185

185-227

227-269

269-311

Soil K (ppm)

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

• 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

Crop Responses to Chloride

Physiological Leaf Spot on Kestrel Winter Wheat

No ChlorideNo Chloride ChlorideChloride

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

Yield Boost from Chloride Depends on Wheat Variety

-6

-4

-2

0

2

4

6

8

10

12

Yie

ld r

es

po

ns

e, b

u/A

Barrie Cora Grandin Karma Kyle

1996 1997 1998

Fertilizer K Management

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+

KClKCl KK22SOSO44

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

Available K SlowlyAvailable K

Unavailable K

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

Fertilizer K Placement

Barley Response to KCl Placement and Rate

N and P added to soil test recommendation SIP Soil Fertility Rpt, 1968

Broadcast

Side band

Seed row

0

5

10

15

20

25

30

0 15 30 60 90 120 150 180 240

lb K2O/A

Gra

in Y

ield

Incr

ea

se

(bu

/A)

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

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

Proportion of roots expected for no K effect (%)

0 20 40 60 80 100

Pro

po

rtio

n o

f ro

ots

ob

ser

ved

in

K s

olu

tio

n (

%)

0

20

40

60

80

100 Corn 17 days old

Be Sure and Use Soil Testing to Monitor Soil K Supplies

Summary—K 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

International Plant Nutrition Institute655 Engineering Drive, Suite 110Norcross, GA 30092-2604Phone: 770-447-0335; Fax: 770-448-0439www.ipni.net

Reference #06111