phosphorus nutrition of soybean

Phosphorus Nutrition of Soybean

Outline –P Nutrition of Soybean

• P uptake by above-ground plant tissue

• Soybean root morphology

• P influx by roots

• Yields and soil test P levels

• P placement

• P timing

• P and soybean pests/diseases

P Uptake by Above-Ground Plant Tissue

Examining uptake throughout the season

Nutrient Uptake by 80 bu/A Soybeans

0

50

100

150

200

250

300

350

400

450

0 20 40 60 80 100 120 140 160

Days after planting

Aer

ial

accu

mu

lati

on

(lb

/acr

e)

N P2O5 K2O

Source: Henderson and Kamprath, 1970

Soybean P Uptake

Days after emergence

Growth stage (inferred)

0 28 56 84 112

10

20

30

40

50

60

70

80

90

100

0

% o

f to

tal u

ptak

e

V1 V6 V10 R4 R6 R7

Beans

Pods

Stems Petioles

Petioles (fallen)Leaves

Leaves(fallen)

Total P uptake:12 – 24 lb P2O5/A

Total P uptake:12 – 24 lb P2O5/A

Source: Hanway and Weber, 1971

Soybean Phosphorus Derivedfrom Fertilizer

Soybean plant fraction P derived from fertilizer

(%)

Leaves (and petioles?) 36

Stems 20

Pods 25

Beans 16

Source: Ham and Caldwell, 1978

Soybean Phosphorus Content Derived from Fertilizer

0

10

20

30

40

50

60

20 40 60 80 100 120

Days after planting

% o

f P

de

riv

ed f

rom

fe

rtili

zer

Soil P level

Low

Medium

High

Source: Bureau et al., 1953

Soybean Root Morphology

Establishing a background for discussions of P placement

Soybean Root Growth

• Phase 1(1st month after planting)

– Rapid vegetative top growth

– Downward taproot growth

– Development of horizontal laterals in upper soil profile

6 in.

Source: Mitchell and Russell, 1971

Soybean Root Growth

• Phase 2(2 – 2.5 months after planting)

– High rates of top growth(from flowering through pod formation)

– More laterals develop in upper soil profile

– Some laterals begin to turn downward

6 in.

Source: Mitchell and Russell, 1971; Raper and Barber, 1970


• Left side:single soybean plant grown in isolated plot

– Primary lateral roots branch from taproot within upper 15 cm (6 in.)

– Below 15 cm (depth of cultivation), taproot degenerated to a root with a diameter similar to primary laterals but with less branching (approx. 10 wk. after planting)

Source: Raper and Barber, 1970


• Right side:soybean grown in 30 in. rows

– Primary lateral roots branch from taproot within upper 15 cm (6 in.)

– Near center of rows (45 cm or 18 in.), laterals angle down sharply as they encounter root zone of neighboring plant

(approx. 10 wk. after planting)

Source: Raper and Barber, 1970

Soybean Root Growth

• Phase 3(Seed set to maturity)

– Continued rapid rates of downward extension of laterals

– Laterals penetrated deeper than the tap root

Depth ofRoot dry weight at the following

days after planting:

sample 31 67 80 102

(in.) -------------- (grams) -------------

0 - 3 0.24 2.60 3.10 4.23

3 - 6 0.04 0.26 0.73 0.52

6 - 9 0.01 0.07 0.12 0.08

9 - 12 0.01 0.04 0.07 0.04

12 - 18 -- 0.05 0.10 0.04

18 - 24 -- 0.03 0.10 0.08

24 - 36 -- 0.07 0.08 0.07

36 - 48 -- -- 0.06 0.06

48 - 72 -- -- -- 0.03

Source: Mitchell and Russell, 1971

Roots Proliferate in Zones of Higher P Concentration

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 0.1 0.2 0.3 0.4 0.5 0.6

P treated soil portion, %

Po

rtio

n o

f to

tal r

oo

t le

ng

thin

P-t

rea

ted

vo

lum

eSoybean

Corn

1:1

Source: Borkert and Barber, 1985

Effects of P or Mycorrhizae on Soybean Shoot Dry Weight

Source: Lambert et al. 1979

Greenhouse studyGreenhouse study

0

0.5

1.0

1.5

2.0

2.5

3.0

0 115 345 920

Applied P rate, lb P2O5/A

Sh

oo

t d

ry w

eig

ht,

gra

ms

0

20

40

60

80

100

% o

f ro

ot

colo

niz

ed

Non- mycorrhizal DM Mycorrhizal DMNon-mycorrhizal infection Mycorrhizal infection

Initial Bray 1 soil test P = 8 ppm

Management Factors Affecting Soybean Root Morphology

• Cultivar choice

– Root angle

– Root elongation rate

• Planting date

– Soil temperature

– Soil moisture

– Photoperiod

– Quantity of radiation

• Tillage– Soil moisture– Soil temperature– Soil bulk density– Soil aeration

• Soil fertility– Plant dry matter

distribution– Root proliferation

• Irrigation– Soil moisture profile

Source: Coale and Grove, 1986

P Influx by Roots

Examining how quickly roots can absorb P

Nutrient Influx by Roots

• Ions are not simply absorbed according to their ratios in solution

• Ions with this characteristic influx pattern require energy to be absorbed

– H2PO4-, HPO4

2-

– K+

• Maximum influx is reached at higher solution concentrations (Imax)

22-23 day old soybean roots22-23 day old soybean roots

-0.5

0.0

0.5

1.0

1.5

2.0

2.5

3.0

0 1 2 3 4 5

Solution P, 10-6 lb P2O5/gal

Infl

ux,

10-1

4 lb

P2O

5 /

(in

2 s)

Imax

Sources: Barber, 1984; Edwards and Barber, 1976

Nutrient Influx Depends on Both P and K Fertility

0.01.02.03.04.05.06.07.08.09.0

10.0

50 70 90 110 130 150

Soil test K, ppm

Infl

ux

, 10-1

3 lb

/ (

in2 s

)

50 70 90 110 130 150

P2O5 influx by soybean roots K2O influx by soybean roots

11 ppm Bray P-1

55 ppm Bray P-1

11 ppm Bray P-1

55 ppm Bray P-1

Low P limits P diffusionand energy for P uptakeLow P limits P diffusionand energy for P uptake

Low P limits energyfor K uptakeLow P limits energyfor K uptake

Source: Hallmark and Barber, 1984

P Influx Varies withPlant Age

-1

0

1

2

3

4

5

0 20 40 60 80 100 120

Plant age, days

Infl

ux,

10-5

lb

P2O

5 /

(in

. d

ay)

Corn

Soybean

Sources: Barber, 1978; Mengel and Barber, 1974

Yields and Soil Test P Levels

Examining how productionlevel is related to soil testP level

Soil Test P Calibration Data

100

80

60

40

20

00 10 20 30 40 50 60 70 80 0 10 20 30 40 50 60 70 80

Soil test Bray P-1, ppm

Rel

ativ

e g

rain

yie

ld,

%

Corn Soybean

Source: Mallarino, 1999

Comparisons of Soil Test P Calibration Data

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35 40

Bray P-1 soil test level, ppm

Re

lati

ve

yie

ld, %

MO IL AR

0 5 10 15 20 25 30 35 40

KY MS AL

Source: Snyder, 2000

P placementBroadcast and bandedapplications

Nutrient Placement Considerations

• Banding:– Less soil volume

fertilized– Smaller portion of

fertilizer is “tied up”– Roots proliferate

where N and P are found

– Rate may be too low to maximize yield

• Fewer roots exposed to supply

• Increase in influx rate by roots may not compensate for fewer total number of roots near P supplies Fertilized soil fraction, %

0 10020 40 60 80

Conceptual model(nutrient deficient soil)

Conceptual model(nutrient deficient soil)

Low nutrient rate

High nutrient rate

Dry

mat

ter

yiel

d

Source: Anghinoni and Barber, 1980

Starter vs. Broadcast:Irrigated Zone

• 3 of 10site-years responded significantly

• pH: 7.6 – 8.1

• Olsen P: 5.6 – 10.7 ppm

• Calcareous soil

• Band placement:2 in. below2 In. to the side (2x2)

-5

0

5

10

15

20

25

0 20 40 60 80 100

P2O5 rate, lb/A

So

ybe

an y

ield

re

spo

nse

, % Broadcast

2x2 Band

Range in average yields:50 - 71 bu/A

Range in average yields:50 - 71 bu/A

Source: Rehm, 1986

Starter vs. Broadcast:Dryland Zone

-10

0

10

20

30

40

50

60

0 25 50 75 100 125

P rate, lb P2O5/A

Yie

ld r

esp

on

se,

%

Source: Bullen et al., 1983

1 in. below

1 in. x 1 in.

With seed

Spring broadcast

Fall broadcast

Starter vs. broadcast:Temperate Rain Fed Zone

• 20 site-years at research stations

• 4 – 29 ppmBray P-1

• 9 sites tested Very Low to Low(6 to 15 ppm Bray P-1)

• 7 of the 9 sites (78%)(6 to 11 ppm Bray P-1) showed significant responses to P

• P placement did not influence soybean yield

3.9 3.9

13.111.6

02468

101214

Bro

adca

st

Sta

rter

Bro

adca

st

Sta

rter

Yie

ld r

esp

on

se,

%

Averaged overall sites

Averaged overresponsive sites

Source: Borges and Mallarino, 2000

Comparison of Placement Combinations and Rates

5.0

7.2

14.0

19.9 19.6

0

5

10

15

20

w/s

eed

band

broa

dcas

t

broa

dcas

t +

w/s

eed

broa

dcas

t +

ban

d

4 10 0 4 10

18 46 60 78 106

5 12 30 35 42Source: Ham et al., 1973

N:

P2O5:

K2O:

Yie

ld r

espo

nse,

%Bray P-1: 3.5 ppmNH4OAc K: 150 ppm

Bray P-1: 3.5 ppmNH4OAc K: 150 ppm

Deep Banding vs. Broadcast

• 20 site-years at research stations

• No-till systems

• 0 – 6 in. soil samples:– 4 – 29 ppm Bray P1

– pH 5.9 – 7.1

• Significant responses to P occurred on 7 sites ranging from 6 – 11 ppm Bray P1

– Average response at these sites:4.6 bu/A

– 5 of the 7 sites showed no differences in placement

30 in.

30 in.

Range in average yields:26 – 63 bu/A


6 - 8 in.


Deep Banding vs. Broadcast

• 11 site-years on farmer fields

• No-till systems

• 0 – 6 in. soil samples:– 5 – 34 ppm Bray P1

– pH 5.8 – 7.5

• Across all site-years, there was a slight(1 bu/A) advantage to P fertilization, and no difference between placement methods

30 in.

7.5 in.

6 - 8 in.




Considerations forPlacement

• Banding is expected to be superior when soil test levels are low and only smaller rates of P are applied

• Broadcast applications may be superior to banded applications when rainfall or irrigation keeps moisture in the upper part of the soil profile

• Placement of bands directly below the seed may be better than other band placements

• Band and broadcast applications used together may be better than either one applied on its own

P TimingComparing fresh andresidual effects of fertilization

Annual vs. Biennial:Broadcast Applications

• Corn/soybean rotation• Long no-till history• P timing (0-46-0)

– Every 2-yr.80 lb P2O5/A

– Every yr.40 lb P2O5/A

• 2 of 4 site-years showedno timing differences

• 1 site (18 ppm Bray P1):annual > biennial by 3 bu/A

• 1 site (37 ppm Bray P1): biennial > annual by 3 bu/A

30 in.



Source: Buah et al., 2000

Annual vs. Biennial:Broadcast Applications

• Corn/soybean rotation

• Long no-till history

• P timing– Every 2 yr.

(0, 30, 80, 160 lb P2O5/A)

– Every yr. (0, 15, 40, 80 lb P2O5/A)

– Direct > residual 2 out of 3 years

– 2 bu/A average response

– Bray P-1: 6 – 14 ppm

10 in.




Annual vs. Biennial:Starter Applications

• Corn/soybean rotation• Long no-till history• P timing (0-46-0)

– Every 2-yr.80 lb P2O5/A

– Every yr.40 lb P2O5/A

• 2 of 4 site-years showedno timing differences

• 1 site (18 ppm Bray P1):annual > biennialby 6 %

• 1 site (37 ppm Bray P1): biennial > annual by13 %

30 in.

30 in.



2 in.

3 - 4 in.


Annual vs. Biennial:Starter Applications

• Corn/soybean rotation

• Long no-till history

• P timing– Every 2 yr.

(0, 30, 80, 160 lb P2O5/A)

– Every yr.(0, 15, 40, 80 lb P2O5/A)

– Annual > biennial 2 out of 3 years

– 2 bu/A average response

– Bray P-1: 6 – 14 ppm

10 in.



30 in.

4 in.


Residual effect of a single, large application of P

40

50

60

70

80

90

100

110

120

1975 1980 1985 1990 1995 2000Year

% o

f yi

eld

att

ain

ed w

ith

600

lb

P2O

5/A

ap

pli

ed i

nit

iall

y, a

nd

67.

5 lb

P2O

5/A

ap

pli

ed a

nn

ual

ly

0 lb P2O5 applied initially67.5 lb P2O5/A applied annually

600 lb P2O5 applied initially 0 lb P2O5/A applied annually

Source: Dodd and Mallarino, 2005

Timing Considerations

• Cases where annual applications may be better than biennial applications in no-till systems:

– Soils with lower soil test levels

– Soybeans planted in narrower rows

• Other tillage systems need to be investigated

• Single, larger applications of P can have significant residual value

– Builds soil test levels

– Can be performed when economics of larger applications are favorable

– Allows P to be omitted in times of unfavorable economic conditions

Phosphorus and soybean pests/diseases

Nutrition and Foliar Diseases:Asian Rust

Rate Upper extent Lesion Type of Overall

N P2O5 K2O of rust lesions density pustule rating

(lb/A)

80 0 0 upper third heavy sporulating susceptible

0 61 0 upper third medium sporulating mod. susceptible

0 0 32 upper third medium sporulating mod. susceptible

80 184 0 upper third heavy sporulating susceptible

27 61 32 middle third medium non-sporulating mod. resistant

Source: Piccio and Fanje, 1980

Nutrition and Diseases:Soybean mosaic virus

K2O

P2O5

Total N + P2O5 + K2O,at equal rates

N

Source: Pacumbaba et al., 1997

05

101520

25303540

4550

0 25 50 75 100 125 150

Nutrient rate, lb/A

SM

V i

nci

den

ce,

%

Nutrition and Nematodes:Soybean cyst nematode (SCN)

02468

1012141618

0-0 30-30 60-60 90-90 120-120

Fertilizer mixture (P2O5 - K2O), lb/A

Cys

ts /

100c

c

0

5

10

15

20

25

30

Yield

respo

nse, %

C/C S/S C/S Yield response

Cultivar highly susceptibleto SCN races 3 and 4Cultivar highly susceptibleto SCN races 3 and 4

Source: Howard et al., 1998

Yield response

Nutrition and Nematodes:Soybean cyst nematode (SCN)

Source: Howard et al., 1998

02468

1012141618

0-0 30-30 60-60 90-90 120-120

Fertilizer mixture (P2O5 - K2O), lb/A

Cys

ts /

100c

c

0

5

10

15

20

25

30

Yield

respo

nse, %

C/C S/S C/S Yield response

Cultivar resistantto SCN races 3 and 4Cultivar resistantto SCN races 3 and 4

Yield response

Conclusions

• At harvest, most of the P in the above-ground portion of soybean is in the grain

• At lower soil test levels, more of the P taken up by the plant comes from applied P

• In the first month after planting, root development is primarily characterized by elongation of the taproot

• In subsequent months, soybean develops much of its root system near the soil surface

• Compared to corn, the rate of P influx by soybean roots is about 4 times slower in the first 20 days

• P proliferates soybean roots when present in concentrated zones

• Mycorrhizae can increase soybean growth at low soil test P levels, even when P is applied

Conclusions

• Soil test calibration data provide a biological evaluation of chemical tests

• Average calibration relationships can be similar across large geographies

• Placement of bands directly below the seed may be better than other band placements

• Band and broadcast applications used together may be better than either one applied on its own

• Annual applications appear to be superior to biennial applications when plant spacing is narrower and soil tests are low

• P can help reduce the incidence and or severity of some soybean diseases

International Plant Nutrition Institute (IPNI)655 Engineering Drive, Suite 110Norcross, GA 30092-2604Phone: 770-447-0335; Fax: 770-448-0439www.ipni.net

phosphorus nutrition of soybean

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