Phosphorus Nutritionof Canola

Outline: P Nutrition of Canola

Photo courtesy of Canola Council of Canada

• What are the nutrient requirements of canola throughout the season?

• Why is P needed early in the season?

• Why is placing P near the seed important?

• How can I be sure P supplies are adequate?

• What are some good strategies for managing P?

NASS; Statistics Canada

What Have the Trends Been in Canola Yield?

Average Yield

Canada 24 bu/A

USA 26 bu/A

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35

1986

1987

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2003

Year

Can

ola

yie

ld, b

u/A

Canada

United States

What Is the Role of Pin Plants?

• Photosynthesis and respiration

• Energy transfer and storage (ATP)

• Cell division and enlargement

• Transfer of heredity traits

• Seed formation

What are the nutrient requirements of canola throughout the season?

Photo courtesy of Canola Council of Canada

• Primary orthophosphate ion:H2PO4

- (pH < 7.0)

• Secondary orthophosphate ion:HPO4

= (pH > 7.0)

• The form most common is a function of soil pH – both equally present at neutral pH

Plants Take Up P As:

Solution P

Johnston et al., 1999

P2O5 & S

N

K2O39 bu/A canola

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140

5 le

af

elongat

ion

full

flower

end o

f flo

wer

50%

podded

full

pod

harve

st

Growth stage

Nu

trie

nt

up

take

, lb

/A

How Much N, P, K, and S Does Canola Take Up

How Are Nutrients Distributed in Canola at Harvest?

Crop removal

0.7 – 0.9lb P2O5/bu

39 bu/A Canola

N P2O5 K2O S0

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180

Nu

trie

nt

con

ten

t, l

b/A

Seed Straw

Seed P and Early Season Canola Growth

• Seed P concentrationcan play a major role in early plant growth

• Seed P has been found to support canola growth for about 7 days

• After that period the seedling requires an external P source, either from soil or fertilizer to optimize growth

Photo courtesy of Canola Council of Canada

Brassica napus Brassica rapa

Canola Plant P Acquisition Strategies

• Canola has been shown to release organic acids from its roots, acidifying the rhizosphere, and increasing soil P availability

• Canola produces longer root hairs than many plants, increasing the soil volume from which it can absorb P

• In addition, canola root hair length and density increases as P supply decreases, further helping to access soil P

Photo courtesy of Neil Harker

P Deficient Canola - Symptoms?

What Role Does FertilizerP Play in Canola Growth?

What Happens to Fertilizer P After I Apply It?

• Absorbed by crop in year 1:– 10 to 30 % of applied P– Highest on low P soils

• Labile P (future years):– 70 to 90% of applied P– Future supply– Metastable Ca-phosphates and

adsorbed P

Solution P Labile P Non-labile P

Response of Canola and Wheat to Fertilizer P

Strong and Soper, 1974

100%

100%

100%

100%

153%

145%

128%

106%

0

0.5

1

1.5

2

2.5

3

3.5D

ry m

atte

r yi

eld

, g/p

ot

Firdale -CK

Firdale -Fert

Lakeland -CK

Lakeland -Fert

TopsRoots

Proportion of Fertilizer P Taken Up by Canola

Karla and Soper, 1968

58%

51%

53%48%

46%

41%

41%

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14

Rosette Bolting Firstflower

Harvest

P u

pta

ke,

mg

/po

t

Soil P

Fert P

Impact of Fertilizer P Placement

Photo courtesy of Roley Rumbold

Why is band placement of P near the seed important?

The primary cause of low short-term uptake of P fertilizer is:

• The inability of P to move to absorbing roots

• Solution:Roots adapt and respond through increased development when they encounter sources of soil and fertilizer P

Pla

nt

roo

t

Higher Pconcentration

Diff

usio

n

Lower Pconcentration

Plant Root Growth in P Band Reaction Zone

Strong and Soper, 1974

• In this pot study, the proportion of plant roots found in a simulated fertilizer band in the soil is shown

• All plants displayed the ability to proliferate root growth in the P fertilizer band area

• Canola was by far the crop which showed the greatest root response to the fertilizer P zone in this non-calcareous P deficient soil

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cen

t o

f ro

ots

in P

ban

d

Canola Wheat Flax

Check

P band

Spring broadcast,

40 lb P2O5/A

Seed-placed,20 lb P2O5/AAgrium

P Placement Can Influence Crop Response

Effect of Seed Row P (as MAP) on Canola Emergence and Yield

Nyborg and Hennig, 1969 10% seed bed utilization

8 bu/A10 bu/A

20 bu/A

17 bu/A

21 bu/A 21 bu/A

lb P2O5/A

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Pla

nt

em

erg

en

ce,

pla

nts

/m2

Seed row 1 in. below row

P2O5 placement

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23

46

What Role Does P Placement Play inCanola Yield?

• Little difference was recorded betweenseed row and banded P when N was banded

• The split of P between 1/3 seed row and 2/3 band shows a minor advantage, and is attributed to those sites with cold soils at seeding

Western Co-operative Fertilizers Ltd. 75 lb N/A + 25 lb P2O5/A

0 5 10 15 20 25 30 35 40

Check

N+Bcst P

N+Band P

N+Seed P

N+2/3 band P, 1/3Seed P

Canola yield, bu/A

What Is the Role of P in Balancing Canola Nutrition?

Photo courtesy Neil Harker

Lafond, 2003

Nitrogen x Phosphorus Interactions

100%

106%

144%

90 N30 P2O5 90 N + 30 P2O5

Fertilizer applied, lb/A

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Can

ola

yie

ld, b

u/A

Hybrid Canola Response to N and P Rates

Karamanos, Unpublished data.

185436

72

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P2O5 lb/A

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10152025303540

0 50 100 150 200N rate, lb/A

Ca

no

la y

ield

, bu

/A

Does P Fertilizer Form Influence Crop Response?

Fixen, 1989; Leikam, 1990

• Research evaluating crop response to MAP, DAP and APP has found that all sources give equal crop response

• In addition, no agronomic differences have been found between dry and liquid sources

• The only exception is rock phosphate which provides limited crop response due to low P solubility

Related Impact of P Nutrition in Canola

Photo courtesy of Canola Council of Canada

• Phosphorus fertilization can lead to earlier maturity of canola – a major factor improving yield and quality in short-season environments

How can I be sure P supplies are adequate?

Photos courtesy of the USDA NRCS

What Information Does a P Soil Test Provide?

• An index of the amountof plant-available P inthe soil

• This index must becalibrated to yield response:

– Examine responses to P additions at various soil test levels

– Conduct studies across a wide range of soil test levels and environmental conditions

Nyborg, 1975

How Is A Soil Test Calibrated to Yield Response?

2 5

0 to 6 ppm P

13 to 19 ppm P

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P O applied, lb/A

Can

ola

yie

ld in

crea

se, b

u/A

Example of P Soil Test Calibration Data

McKenzie et al., 1995

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Kelowna P, ppm

Re

lati

ve

yie

ld,

%

• Calibration curve indicates which soil test levels tend to limit yields

• Data based on P responses observed across several sites and years

Critical Soil Test P Level

• The results of this calibration data set from Alberta show a critical level of 20 to 25 ppm (40 to 50 lb/A) P

• This is the level of soil test P above which only maintenance (starter/removal) application would be required

McKenzie et al., 1995

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Kelowna P, ppm

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%

What Are the Best Uses for Soil Test P Information?

—Estimating average probabilities of crop response—Examining changes in levels over time

—Estimating average relative yield response

—Estimating a specific probability of response for a given site and year

—Estimating a specific relative yield response at a given site and year

Good

Fair

Poor

What are some good strategies for managing P?

Photos courtesy of the USDA NRCS

Approaches to P Fertilization

• Sufficiency approach:Apply P to maximizenet returns to fertilizationin the year of application

– Strategy: fertilize onlywhen there is a goodchance that a profitableyield response will be realized

– Soil test levels kept in lower, responsive ranges

– Normally adopted on land leased for short periods of time or when cash flow is limited

Rel

ativ

e yi

eld

, %

Soil test P level

Approaches to P Fertilization

• Build and maintenanceapproach:Remove P as ayield-limiting variable

– Strategy: apply extra P(more than expectedcrop removal) to buildsoil tests to levels thatare not yield-limiting

– Soil test levels kept in higher, non-responsive ranges

– Normally adopted on owned land or land leased for longer periods of time

Rel

ativ

e yi

eld

, %

Soil test P level

Summary -P Nutrition of Canola

• P nutrition is critical to reaching the attainable yield potential of canola

• Canola responds to P deficiencies by changing its root development, forming more root hairs

• Canola will concentrate its roots in the area of P fertilizer bands, increasing fertilizer recovery

• P nutrition must be part of a management strategy that considers the importance of other nutrients

• Land ownership/rental and cash flow have a large impact on the approaches taken to managing soil fertility

Ref: 06128

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