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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,
%
Fertilizer K2O, lb/A
Alfalfa responseto K at two sites
Most EconomicRate
Beegle, 1992 (PA)
Initial soil test K rangedfrom 130 to 170 ppm
Response to K IncreasesOver Life of Stand
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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
Response to K IncreasesOver Life of Stand
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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
Fertilizer K2O, lb/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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Burmester et al., 1991 (AL)
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
Burmester et al., 1991 (AL)
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
Burmester et al., 1991 (AL)
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