K Nutrition of Alfalfa

7/28/2019 K Nutrition of Alfalfa

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Potassium Nutritionof Alfalfa


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Potassium (K) Nutritionof Alfalfa

Outline:1. Plant development

2. Diagnosis

3. Yield and quality4. Economics

5. Irrigation and record yields

6. Cation competition

7. Balanced nutrition


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Alfalfa Production

U.S. Alfalfa Production and Yield

0

5

10

15

20

25

30

1920 1940 1960 1980 2000

Millionac

res

0

1

2

3

4

5

6

Yield(ton/A)

Production

Yield

In addition, Canada has 11 million acres yielding 1.4 ton/A U.S. crop value $7 billion per year, 2000-2003

USDA-NASS; Statistics Canada


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Alfalfa Root Development

Most lateral roots are near the soilsurface for the first year, but more deeplateral roots develop as the plant ages

Alfalfa has lower root density than many

grasses and a deeper rooting zone Nutrient applications increase root

growth, enabling roots to obtainmoisture and nutrients from greater

volume of soil


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Alfalfa Root Morphology(Approximately 2 Months after Planting)

Dryland Deeper penetration

Fewer but longer laterals

More secondary branches

Irrigated Shallower

More but shorter laterals

Less secondary branches

Weaver, 1926 (NE)

Dryland Irrigated


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Alfalfa Root Morphology(Approximately 3 Months after Planting)

Dryland Root system is more

profusely branched

Branches reached samedepth as tap root

Shallower root system

Irrigated

Fewer branches

Greater rooting depth

Tap root is the dominantstructure Dryland Irrigated

Weaver, 1926 (NE)


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Alfalfa Root MorphologyEnd of First year

Dryland Greater number of branches in

upper 1 ft. of soil

Maximum depth of 5 ft.

Roots oriented downward Irrigated

Fewer branches in upper 1 ft. ofsoil

Maximum depth of over 6 ft.

Greater lateral extent of rootsystem

Dryland Irrigated

Weaver, 1926 (NE)


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Alfalfa Root MorphologyJuly 10, Second Year

Dryland Depth of over 9 ft.

Roots oriented downward

Little lateral extension

Irrigated Depth of nearly 10 ft.

Greater lateral extention

Irrigated

Weaver, 1926 (NE)

Dryland


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Factors Restricting RootGrowth Reduce NutrientUptake

Disease damage

Insect damage

Temperature Acidity

Low oxygen

Poor drainage

Excess salt or sodium

Nutrient deficiencies

Poor nodulation

Soil compaction


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Recovery of K fromVarious Soil Depths

Depth of placement, in. Recovery, % of applied

Surface 41

0-6 29

6-12 19

12-18 16

18-24 10

30-36 11

Recovery at the end of the growing season with K placed in theSpring at various depths in an established alfalfa stand

Peterson and Smith, 1973


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Diagnosis of NutrientDeficiencies

Visual Observation Soil Testing

Tissue Analysis


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In K-deficient alfalfa, smallwhite or yellowish spotsfirst appear around the

outer edges of older leaves


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K Deficiency in Alfalfa

Moderate K Deficiency Severe K Deficiency


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Typical K Concentrations(at optimum fertility)

Stems near top ofplant contain themost K

Leaf K concentration

is similar amongupper and lowerleaves

Roots contain less K

Forage containing2.5% K removes 60 lbof K2O per ton of drymatter harvested

Plant part and

growth stage

K, % on dry

matter basis

Stems: near groundlevel

2%

Stems: near top up to 6%

Leaves: 1.8 - 2.2%

Roots: 1.1%

Forage harvested atearly bloom:

1.8% to 2.5%

Top 6 in. at bud to earlybloom:

2.0% to 3.5%

Lanyon and Smith, 1985


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K Concentration Declineswith Maturity

Barton and Reid, 1977 (WV)

0

1

2

3

Vegetative Bud Early

Bloom

Full

Bloom

Seed

Growth Stage

ShootK,

%


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Soil Testing andPlant Analysis

Soil Testing Verify that K levels are being maintained

Soil pH 6.5 or higher for efficient N fixation

Plant Analysis

Usually sample the top 6 in. at harvest Indication of adequate K fertility:


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K Deficiency HurtsMore Than Yield

Adequate K Improves: Plant persistence

Number of shoots per plant

Shoot yield

Deficient K: Reduces root starch storage

Reduces protein concentration in root

Results in poor survival and slow

shoot growth

Li et al., 1997 (IN)


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0

10

20

30

40

50

60

70

Nodule number Nodule weight, mg

0 21 43 64 86 107K2O added, lb/A

Grewal and Williams, 2002 (Australia)

K Fertilization IncreasesNodule Activity


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0

20

40

60

80

100

Leaf Drop (%) Leaf Spot

Rating

Leaf/Stem Ratio

(x100)

0 21 43 64 86 107K2O added, lb/A

K Fertilization ImprovesHay Quality

Grewal and Williams, 2002 (Australia)


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Plant counts taken in May as % of those previous September

Bailey, 1983 (MB)

K Helps Reduce Winterkillin Alfalfa

100

1971 1972 1973 1974 1975 1976 19770

20

40

60

80

Standdensity(%)

100 lb K2O/yrNo K

Year


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Alfalfa Responses to Kin Mixed Stands

Largest where soil K fertilitylevels are low

Increases over the lifeof the stand

Includes quality as wellas yield

Increased proportion oflegume to grass more protein

Increases in irrigated production


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0 100 200 300 400

3

4

5

16

17

18

19

Hayyield,

tons/A

Fertilizer K2O, lb/A

Initial soil test K

was 35 ppm (low)

4-yr total

19891992

1990

1991

Most EconomicRate

Klausner and Goyette, 1993 (NY)

Response to K IncreasesOver Life of Stand


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4

5

6

7

0 200 400 600

2.0

2.5

3.0

0 200 400 600

1989

1990

1991

Rock Springs Landisville

Yi

eld,

tons/A

Forage

K,

%


Alfalfa responseto K at two sites

Most EconomicRate

Beegle, 1992 (PA)

Initial soil test K rangedfrom 130 to 170 ppm



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Berg et al., 2003 (IN)

0

5

10

15

2025

30

35

0 100 200 300 400

Cumulativeyiel

d,

to

1998 1999 2000 2001 2002

Added K, lb K2O/A

Greatestresponseoccurred in5th year



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6

7

8

9

0 100 200 300 400 500

2.0

2.5

3.0

3.5

Yield,

tons/A


ForageK

,%

Most EconomicRate

1985

1986

Sheard et al., 1988 (ON)

1985

1986

Response increases afterintensive management

Alfalfa response to Kunder intensive 5-cutmanagement

Initial soil test K of

170 ppm in 1984,declined to 80 ppm inthe unfertilizedtreatment by spring1987

S K L


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Soil K Levels:Turn K Fertilizationinto Profit

Example: Annual economic returnto K fertilizer use:

Assuming $90 per ton of hay and K2O at$0.15 per pound (price ratio of 3 lb hayper lb of K2O)

Soil test Kcategory

Yieldresponse

K2O rate Netreturn

tons/A lb/A $/A

Very low 1.2 335 57.75

Low 1.0 260 51.00

High 0.2 90 4.50


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Economics ofK Fertilization

The most economic rate of K fertilization changes as theratio of K prices to hay prices changes

Soil Test KPrice Ratio

Category 2 3 4 5

Most economic rate of K2O (lb/A)

Very low 425 335 270 220

Low 330 260 214 175

High 130 90 60 40


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Profitability:Short vs. Long-Term

The yield increase in response to K application getslarger as the alfalfa stand ages

Alfalfa Yield Response to Annually Applied K

0.00.5

1.0

1.5

2.0

2.5

1 2 3 4 5 6 7

Age of stand, years

Yield

response,

ton

Quebec

Pennsylvania

New YorkManitoba

Missouri

K Fertilization According to


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Burmester et al., 1991 (AL)

0

4

8

12

16

120 240 440 550 640

K2O application rate, lb/A

Alfalfa

standdensit

y,plants/ft2

K Fertilization According toSoil Test RecommendationMaintains Alfalfa Stands

Recommended K rate


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Follet and Wilkinson, 1995

0

1

2

3

4.5 5 5.5 6 6.5 7

Soil pH

Yield,tons

/A

Alfalfa Response to Soil pH

Liming Acid Soil Improves


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Walworth and Sumner, 1990 (GA)

Liming Acid Soil ImprovesAlfalfa Growth andNutrient Recovery

0

2

4

6

8

0 2100 3400

Lime added, lb/A

Yr 1Yr 1Yr 1

Yr 2

Yr 2Yr 2

Yr 3

Yr 3

Yr3

pH 5.3

pH 6.1

pH 4.7

Alfalfayield,

ton/A

Liming Acid Soil Improves


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Liming Acid Soil ImprovesAlfalfa Growth and NutrientRecovery

Walworth and Sumner, 1990 (GA)

0

1

2

3

N K Ca

pH 4.7

pH 5.3

pH 6.1

Alfalfashootcom

position


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How Does this Changewith Irrigation?


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Record Yield:Researchers at University of Arizona(Yuma) set record for alfalfa yieldin a year:

24.1 tons/A alfalfa hay in10 cuttings

Optimal and uniform irrigation

Chopped hay removed immediately after cutting

N fertilizer regularly added was it needed?

460 lb P2O5/A added before planting

K management unknown


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0

2

4

6

8

10

12

14

16

Cumula

tiveHayYie

ld,

Tons

K2O rate, lb/A

0 200 400 600 600

Optimum K Rate in IrrigatedAlfalfa: An Example

Koenig, 2002 (UT)

Too

muchin

one

application


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Placement and ApplicationOptions

Establishment Broadcast to build up soil test K before seeding

Banded starters should contain mostly P

Maintenance

Apply following harvest to replace removal High rates: split over several cuts to avoid salt injury

To boost winter hardiness, apply before critical fall growthperiod (before last 6 weeks of growth)

When soil K levels are high, spring applications can lead tohigher K levels than desired, and may be unnecessary

F


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Yield response to K found in last harvest of 2000 For first harvest of 2001, no response to K fertilization was observed

Reason:K can be released from soil minerals during winter and spring

Volenec, 2002 (IN)

K Impacts Fall Harvestmore than Spring

0

0.3

0.6

0.9

1.2

0 100 200 300 400

Hay

yield,

ton

Fall Harvest, 2000

K applied, lb K2O/A)

0

0.3

0.6

0.9

1.2

1.5

1.8

0 100 200 300 400

Hay

yield,

ton

Spring Harvest, 2001

K applied, lb K2O/A


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Manure Management

Manure supplies many nutrients but usually not in the ratio required

for alfalfa!

Physical problems

compaction, crown damage,leaf burn, salinity

Nutritional problems

N can stimulate weeds

excessive K can cause cation

imbalance in dairy feed rations

L U K


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Luxury Uptake of K forDairy Feed

K in alfalfa varies from3%

Luxury uptake when soil Kis very high

K levels above 3% unnecessary

Liquid manure systems efficientlyrecycle K

High K forage: A concern fordry dairy cows

Leads to milk fever, retained placentas after calving For the transition period (2 to 4 weeks before calving) forage

with


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0

0.1

0.2

0.3

0 150 300 450 600

K applied, lb K2O/A

TissueMg

,%

Magnesium Concentrations in Alfalfa

K Competes with OtherCations for Plant Uptake: Mg

K C O


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0

0.4

0.8

1.2

1.6

0 150 300 450 600

K applied, lb K2O/A

TissueCa

,%

Calcium Concentrations in Alfalfa

K Competes with OtherCations for Plant Uptake: Ca


K Fertilization Reduces


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K Fertilization ReducesUptake of Other SoilCations: NA

0

500

1000

1500

2000

2500

3000

0 100 200 300 400

James, 1988 (UT)

Sodium Concentrations in Alfalfa

K applied, lb K2O/A

Sodium,p

pm

Balanced P and K Nutrition Is


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0

1

2

3

4

5

6

78

1998 1999 2000 2001 2002

No P or KP only

P and K

Alfalfahayyield,t

on/A/yr

Berg et al., 2003 (IN)

Balanced P and K Nutrition IsEssential for Optimal Yieldsand Stand Maintenance

Fertilization According to


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Recommended K rate

02

4

6

810

12

14

16

120 240 340 440 540 640

Yr 3

Yr 2

Yr 1

Yield,to

ns/A

K applied, lb K2O/A

Fertilization According toSoil Test Recommendations


Summary


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SummaryK Nutrition of Alfalfa

Alfalfa takes up and removeslarge amounts of K from the soil

Fertilization is essential for highyields, stand longevity,

and winter hardiness Fertilized to optimum, forage

contains 2 to 3% K

Application: pre-plant and following harvests

Apply recommended rates to avoid luxury uptake


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International Plant Nutrition Institute (IPNI)

655 Engineering Drive, Suite 110

Norcross, GA 30092-2837

Phone: 770-447-0335; Fax 770-448-0439Website: www.IPNI.NET

K Nutrition of Alfalfa

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