Keith JohnsonForage Crops Specialist

(765)494-4800 johnsonk@purdue.edu

Impact of Cutting Management and Soil Fertility on Winter Survival

I appreciate the contributions of Dr. Jeff Volenec.

ObjectiveImprove winter survival of alfalfa with use of “Best Management Practices”

Critical Periods for Alfalfa Growth and Development

Seedling establishmentHerbage regrowth after harvestFall growth and its impact on winter hardiness (and ultimate survival)Spring growth and first harvest yield

Calculating Risk of Alfalfa Winter Injuryfrom: NCR 547 Alfalfa Management Guide

FactorsStand ageAlfalfa varietySoil pHExchangeable K levelSoil drainageSoil moisture during fall/winterHarvest FrequencyHigh stubble with a late harvest

Calculating Risk of Alfalfa Winter Injuryfrom: NCR 547 Alfalfa Management Guide

FactorsStand ageAlfalfa varietySoil pHExchangeable K levelSoil drainageSoil moisture during fall/winterHarvest FrequencyHigh stubble with a late harvest

People do

have some control!

Poor GoodBetter

Varieties Differ in Persistence

Later Seedling Development Involves Contractile Growth That “Pulls” the Cotyledonary Node (CN) Below the Soil Surface Forming the Crown

Source: Forages Vol. I, 6th Edition

CN

CN

Soil surface

Nodules(pink)

Alfalfa Crown With 2 Inches of Contractile Growth - Enables Alfalfa to Tolerate Mowing/Grazing and

Also Key to Winter Survival

Cotyledonary Node

Heaving Caused By Freeze-Thaw Cycles in Late Winter Reverses Contractile Growth Exposing Crowns and Taproots to Hazards of Mowing and the Extremes of Winter Weather

Greatest concern with high clay content soil with poor percolation

Don’t be surprised. Routinely scout the fields.

Taproots Anchor the Plant, Assist with Nutrient Uptake, and Store Organic Reserves Essential for Shoot Regrowth

Fall Dormancy=1Most dormant

Fall Dormancy=4Common to Midwest

Fall Dormancy=9Least dormant

Large Differences in Fall Dormancy Exist, and This Trait is Positively

Associated with Winter Hardiness

Dormant Nondormant

Autumn picture

Nondormant alfalfa is like diet soda, whereas dormant alfalfa is like normal soda when put in a

freezer. Which freezes first?

Genetic Selection for Greater Fall Dormancy Reduced Winter Injury

Height in Autumn, cm0 10 20 30 40 50

Win

ter I

njur

y(1

=uni

njur

ed, 2

=inj

ured

, 3=d

ead)

1.0

1.5

2.0

2.5

3.0

Year 1Y=1.12+0.035x

R2=0.88**

Year 2Y=0.4+0.046x

R2=0.81**

4 in. 16 in.

Past Research……...(Smith, 1964)

“The fact that plants have high carbohydrate reserves does not mean that they will necessarily develop a high degree of hardiness, but as carbohydrates are the main source of energy, plants low in these reserves cannot develop a high level of hardiness.” Taproot Starch, mg/g dry wt.

140 160 180 200 220 240 260

Leth

al T

empe

ratu

re 5

0

-20

-18

-16

-14

-12

-10

-8

Y=-55+0.37x-0.0007x2

R2=0.61*

Adapted from Castonguay et al., 1995

The Rankings of Winter Hardiness and Root Raffinose Family Oligosaccharide Concentrations

Have a Near-Perfect Correlation – Sucrose Does Not

Rank of Sucrose or Total RFO1 2 3 4 5 6 7 8 9 10 11 12

Ran

k of

Win

ter H

ardi

ness

123456789

101112

Total RFOY=0.3+0.96xr2=0.92**

SucroseY=2.0+0.69xr2=0.48*

Impact of Harvest Management

Herbage Regrowth After Harvest in Summer Depends Upon Stored Reserves in Taproots

05

1015202530354045

0 14 28 42 56 70 84 98

Days From May 25

Tap

roo

t S

tarc

h,

%

*=Harvest Date

*

* *

12”12”

12”

Frequent Harvesting in Summer Depletes Taproot Reserves and Reduces Yield and

Persistence

05

1015202530354045

0 14 28 42 56 70 84 98Days From May 25

Tap

roo

t S

tarc

h,

%

*= 35-day Harvest Interval*

* *

12”

12”12”

@=Biweekly Harvests

Accumulation of Stored Reserves is Key to Herbage Regrowth and Plant Survival.Pushing hard if number of harvests >4 in a year.

Alfalfa Taproot Reserves Accumulate in Autumn and are Necessary for Winter Survival

0

5

10

15

20

25

30

35

40

45

0 15 30 45 60 75 90 105 120Days From September 1

Tap

roo

t S

tarc

h,

%

Harvest

Oct. 1 Nov. 1 Dec. 1

No FallHarvest

Avg. KillingFrost

High TaprootStarch

Fall Cutting Management Influences Alfalfa Taproot Reserves and Winter Survival

0

5

10

15

20

25

30

35

40

45

0 15 30 45 60 75 90 105 120Days From September 1

Tap

roo

t S

tarc

h,

%

Harvest

Oct. 1 Nov. 1 Dec. 1

No FallHarvest

Avg. KillingFrost

Low Taproot Starch

Fall Harvest prior to killing frost

Fall Cutting Management Influences Alfalfa Taproot Reserves and Winter Survival

0

5

10

15

20

25

30

35

40

45

0 15 30 45 60 75 90 105 120Days From September 1

Tap

roo

t S

tarc

h,

%

Harvest

Oct. 1 Nov. 1 Dec. 1

No FallHarvest

Avg. KillingFrost

Low Taproot Starch

Harvest inEarly Oct.

Plant Survival Over Winter and Shoot Growth in Spring Depends on Taproot Reserves

0

5

10

15

20

25

30

35

40

45

0 15 30 45 60 75 90 105 120 135 150

Days From January 1

Tap

roo

t S

tarc

h,

%

Jan. Feb. Mar.

Ready forHarvest 1

ShootGrowthAppears

Apr. May

CHO Used ForRespiration

Plant Survival Over Winter and Shoot Growth in Spring Depends on Taproot Reserves

0

5

10

15

20

25

30

35

40

45

0 15 30 45 60 75 90 105 120 135 150

Days From January 1

Tap

roo

t S

tarc

h,

%

Jan. Feb. Mar.

Ready ForHarvest 1

ShootGrowthAppears

Apr. May

CHO Used ForRespiration

MismanagedPrevious Fall

October Cut

October Uncut

Spring Vigor is Reduced by Fall Cutting

As expected, fall cutting Increased winter injury.

Fall cutting also reduced spring vigor (measured as shoot length)

Q60 H69 P51 NO2 P55 5939

10

15

20

25

Win

ter i

njur

y

1.00

1.25

1.50

1.75

2.00

2.25CutUncut

Plan

t hei

ght i

n A

pril

(cm

)A

B

(1 =

no

inju

ry, 3

= d

ead

plan

t)

From Haagenson et al., 2003Dormant Semidormant Non-

dormant

Impact of Cutting Management on Winter Survival

Harvested mid-OctNo harvest mid-Oct

Impact of P and K Fertility

Low K and P High K and P

360K 66P

0K 0P

Classic K deficiency

+K +P

-K +P

+K -P

Regrowth- 1 Week Post-Harvest

Balance, Balance, Balance

360 K 0 P

0 K, 66 P 180 K, 44 P

270 K 0 P

April 1999

360 K 0 P

0 K 66 P 180 K 44 P

270 K 0 P

May 2004

300K-75P 0K-0P

270K 44P 0K 44P0K 22P

90K 66P 270K 22P

May 19,2003: First Hay Harvest

Severe Stand Losses Have Occurred Where P Has Been Applied Without K

Balance, Balance, Balance

Yield Component Analysis Permits Us to Understand How Alfalfa Responds to Improved P and K Nutrition

Yield=plants/area x shoots/plant x mass/shoot

Shoots/area

Yie

ld, 0

K/0

P in

19

98

=1

00

%Yield was Increased by 0K/66P in 1998 to 2000, But Resulted in the Lowest Yields in 2002 to 2004

0

20

40

60

80

100

120

140

1998 1999 2000 2001 2002 2003 2004

0K 0P0K 66P360K 0P360K 66P

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1998 1999 2000 2001 2002 2003 2004

0K 0P

0K 66P

360K 0P

360K 66P

Mas

s pe

r Sh

oot,

gMass per Shoot MimickedTrends in Forage Yield

0

20

40

60

80

100

120

140

1998 1999 2000 2001 2002 2003 2004

0K 0P0K 66P360K 0P360K 66P

0

10

20

30

40

50

1997 1998 1999 2000 2001 2002 2003 2004

0K 0P0K 66P360K 0P360K 66P

Pla

nts

per

ft2

Plant Density Declines For All Fertility Treatments, and is Not Closely Associatedwith Forage Yield

Death occurs in summer not winter

0

20

40

60

80

100

120

140

1998 1999 2000 2001 2002 2003 200

0K 0P0K 66P360K 0P360K 66P

0

10

20

30

40

50

60

70

1998 1999 2000 2001 2002 2003 2004

0K 0P0K 66P360K 0P360K 66P

Shoo

ts p

er S

quar

e Fo

ot

Forage Yield Was Not Associated With Shoots/ft2in 1998 to 2001, While K Fertilizer ApplicationIncreased Shoot Density in 2003 and 2004

0

20

40

60

80

100

120

140

1998 1999 2000 2001 2002 2003 2004

0K 0P0K 66P360K 0P360K 66P

Plant Population versus Time

Dec 97

May 98

Dec 98

May 99

Dec 99

May 00

Mar 01

May 01

Dec 01

May 02

Dec 02

May 03

Plan

t Pop

ulat

ion,

pla

nts/

m2

0

100

200

300

400

500

LSD.05=14

Summer Plant Disappearance

A Final Word on Alfalfa Stand. . . . .

Fewer shoots are needed for an economic stand when proper attention is given to the P and K fertilizer needs of the alfalfa.

Mass per shoot is most closely associated with yield.

Loss of stand mostly occurs during the summer. Does this result because of cumulative stress from mismanagement other times of the season?

Balance, Balance, Balance

Alfalfa possesses high tolerance to physical stress, including defoliation and cold. Our management, however, does make a difference.

Questions?