Phosphorus... Essential for Life

Dr. Mark D. StaufferDr. Mark D. Stauffer

President, Potash & Phosphate Institute of CanadaPresident, Potash & Phosphate Institute of CanadaSenior Vice President, Potash & Phosphate InstituteSenior Vice President, Potash & Phosphate Institute

Phosphates are a vital ingredient in the diets of all living things…

• is the second most abundant mineral nutrient in the human body

• 80% of P in humans is in bones & teeth accounting for 20% of the mineral ash & 1% of total body weight

• The remainder is widely distributed throughout the body, in combination with fats, proteins and salts in every cell

Phosphorus is of universal importance to every living cell…

• Nucleic acids (DNA, RNA, genes, chromosomes)

• Proteins• Lipids• Sugars• Enzymes• Energy rich P compounds

(ATP, ADP)

is incorporated into…

Phosphate chain

ATP: Nature’s energy store

“Without phosphorus, there is no cell, no plant, and no grain…

Without adequate phosphorus, there is a lot of hunger…”

• Energy storage & transfer for every biological process

•photosynthesis•respiration•cell division, development, enlargement,

gene transfer, reproduction

is critical to basic plant physiology:

Impact on crops

Vigorous crop (Shoot/Root) growthImproved resource utilization

• water, nutrients• positive environmental implications

Better resistance to stress

• disease, pest, moisture, temperature

Earlier maturity

• good grain & fruit development• better crop quality, yield

LOWERSFARMER

RISK &

RAISES PROFIT

POTENTIAL

Growing Degree Units

Kg

P /h

a

Grain (Wheat)

Head

Stem

Leaves

30

25

20

15

10

5

0

(Jacobsen et al. 1992)

04/19

3005/10

6006/03

9006/19

12007/13

15007/31

18008/13

is mobile in the plant…linked to metabolic processes…& is concentrated in the most active areas of growth

• the majority of P is removed in fruit/grain

Corn Grain 0.22Stover 0.17

Cotton Seed 0.66Stalks 0.24

Soybeans Grain 0.42Straw 0.18

Wheat Grain 0.42Straw 0.12

Crop Plant part P content, %

Agronomic characteristics of P deficiency

… purpling of leaves / stems

… darkened leaves

• reduced leaf number, expansion & surface area

deficiency reflected in poor development at all stages…

• stunted growth

Impact on plant roots & tillers (wheat)

0 45 90 135 180 225 270 315 360

9

12345678

1011121314

P2O5 Rate, lb/A

Num

ber o

f Adv

entit

ious

Roo

ts a

nd T

iller

s/P

lant

Tillers

Roots

(Fanning and Goos 1992)

80 N

40 N

0 N

Impact on water use efficiency (wheat)

40 0 26 -1340 45 42 4040 90 49 63

0 0 30 ---0 45 38 270 90 40 33

N P2O5 WUE Increase

kg/ha kg/cm H2O in WUE, %

Impact on nutrient use efficiency (wheat)

0

100

200

300

400

500

600

0 60 120 180 240

N rate, kg/ha

Wheat K uptake, kg/ha

64kg P

16kg P

0kg P

(Schwartz and Kafkafi)

(Schlegel, Dhuyvetter, and Havlin, 1996)

Impact on residual soil nitrate & leaching

0

50

100

150

200

0 40 80 120 160 200

N rate, kg/ha

Soi

l NO

3-N

in u

pper

3 m

, kg/

ha

without Pwith P

At optimum N rate P reduced residual nitrate by 66 %

soil profile NO3-N after 30 years…

Impact on crop maturity (barley)

104106108110112114116118

0 13 27 40

P2O5 Rate, kg/ha

Day

s to

Mat

urity

of B

arle

y

Site 1Site 2

(Westco – Alberta, Canada)

Impact on yield & cost of production

Schlegel, Dhuyvetter, and Havlin, 1996

40

50

60

70

80

90

100

110

120

130

140

0 22 45 67 90 112 134 157 180 202 224

N rate, kg/ha

Cos

t of p

rodu

ctio

n, $

/t

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

13000

Yiel

d, k

g/ha

with P

without P

30 year average

OrganicInorganic

Soil Test

How much P is in the soil?

• 4 kg P/ha or less is plant-available in soil solution.

• An actively growing crop can use up all of the P in soil solution twice a day.

• A soil’s ability to maintain a plant-available P supply is the important factor.

Soil Solution

The Phosphorus Cycle

Plantuptake

Soil solutionphosphorus•HPO4

-2

•H2PO4-1

Primaryminerals(apatite)

Wea

therin

gSecondarycompounds

(CaP, FeP, MnP, AlP)

Dissolution

Precipitation

Mineralsurfaces

(clays, Fe and Al oxides)

Adsorption

Desorption

Organic phosphorus•Microbial•Plant residue•Humus

Mineralization

Immobilization

Crop harvest

Runoff anderosion

Leaching(usually minor)

Loss

Animalmanures

and biosolids Mineralfertilizers

Plant residues

Input

0

20

40

60

80

100

Low Medium SufficientSoil Test P

PotentialEnvironmental

Problems?

Rel

ativ

e cr

op y

ield

, %

(Sharpley et al. 1993)

Risk of environmental loss?

• Soil tests are good indicators of dissolved P in runoff …… BUT do not indicate environmental risk for a given field

Phosphorus in the Watershed

Sharpley, Gburek, USDA-ARS; Beegle, Penn State University

Soil Test P Distribution

Mehlich-3 Pmg/kg<30

30-100>100

Sharpley, Gburek, USDA-ARS; Beegle, Penn State University

Vulnerability to P LossP loss

vulnerabilityLow (clear)

MediumHigh

Sharpley, Gburek, USDA-ARS; Beegle, Penn State University

What Determines Phosphorus Fertilizer Need?

Population, Land resources/fertility, Historic nutrient use patterns, Cropping diversity,

Export versus domestic goals, Government policy, Current Economy…

ƒ

Highly P def soils> 60%

20-40%40-60%

0-20% (Fairhurst et al., 1999)

Indigenous Phosphorus supply - the net effect?

0.0

0.5

1.0

1.5

2.0

2.5

3.0

1961 1966 1971 1976 1981 1986 1991 1996 2001

US - t/ha

Brazil - t/ha

Soybean yields – US/Brazil

AgriStats, NASS

0

10

20

30

40

50

60

70

80

1961 1966 1971 1976 1981 1986 1991 1996 2001 2006

Milli

ons Brazil - Area (ha)

Brazil Production (t)US - Area (ha)US - Production (t)

?

Soybean growth – US/Brazil

AgriStats, ANDA, NASS

0

100

200

300

400

500

600

700

800

900

1,000

1,100

1961 1966 1971 1976 1981 1986 1991 1996 2001 2007

Thou

sand

s US, t

Brazil, t

Soybean P removal – US/Brazil

AgriStats

EC Joint Research Centre, 2002

Opportunities…• World food demand

• Favorable climate

• Lower land price

• Low production cost

• High yields with fertility correction

• Improving infrastructure

• Political/economical stability

Smallholder farms - Sustainability of Slash & Burn Systems – Oxisol, Manaus, Brazil

Cravo and Smith, 1997

• 8 years of cultivation after initial slash & burn• 17 consecutive crops

1 2 3 4 5 6 7 8Year After Burning

CROPRiceSoybeanCornCowpea

TREATMENTN & PKLime & CuSB & ZnMnMg

0

600

1,200

1,800

2,400

1982 1983 1984 1985 1986 1987 1988 1989

Yie

ld, k

g/ha

RiceSoybeanCowpeaCorn

0

20

40

60

80

1984 1985 1986 1987 1988 1989

Yie

ld, k

g/ha

SoybeanCowpeaCorn

No fertilizer:• Total yield = 1.73 t/ha

Cravo and Smith, 1997

Soil fertility decay pattern – No fertilizer

Cravo and Smith, 1997

Months till 50% Decrease Increase

Org C 134 -Ca 23 -Mg 15 -K 5 -Al - 33pH - 29Zn 21 -

0

600

1,200

1,800

2,400

3,000

3,600

1982 1983 1984 1985 1986 1987 1988 1989

Yie

ld, k

g/ha

RiceSoybeanCowpeaCorn

NPK plus Lime

Cravo and Smith, 1997

1 3 5 7 9 11 13 15 170

10

20

30

Yield Response to P

Crop Number

Cum

ulat

ive

yiel

d, t/

ha

Applied Pkg/ha

396

264

132

Control

Cravo and Smith, 1997

• plus 3 t Aglime

**Subsistence farmers require clearing & abandoning 3 new hectares per year to produce the same amount of food on one sustainable hectare

Gypsum+Lime+PK =3,780 kg/ha

Seed only = 480 kg/ha

Cerrado soil has poor fertility & can’t produce without fertilizers

Dirceu Broch, Fundação MS

4.86.0

13.5

12.0

4.0 4.0

8.0

5.0

3.55.0

0

2

4

6

8

10

12

14Y

ield

, t/h

a

Rice Corn Beans Soybean Wheat

BrazilCerradoGood farmersExperimentalShort/Med Goal

Compiled from Lopes, 1996 and Yamada, 2003

Grain production gaps

Soybean P response in Cerrado soil

Source: Fundação MT

0

1,500

3,000

4,500

Yie

ld, k

g/ha

0 80 160 240

033

83114

132

Broadcast & Incorporated, kg P2O5/ha

Seed placed, kg P2O5/ha

3,310

3,220

4,210

640

TOP FARMER GROUPS: TO DEVELOP AND TRANSFER TECHNOLOGY

Challenges

• Potential for agricultural expansion is great

• Projections for future production are bold

• Maximum economic yield is always the desired goal

• Adequate P is a crucial part of the yield equation responsible for reaching this goal

• How sustainable is this production?

0

20

40

60

80

100

120

140

1961 1964 1967 1970 1973 1976 1979 1982 1985 1988 1991 1994 1997 2000

USAChinaIndiaFranceArgentinaBrazil

P consumption – world comparisons (kg per arable ha)

AgriStats

0

10

20

30

40

50

60

70

80

1961 1966 1971 1976 1981 1986 1991 1996 2001

Milli

ons Brazil - Area (ha)

Brazil Production (t)US - Area (ha)US - Production (t)

Soybean growth – US/Brazil

AgriStats, ANDA, NASS

pH &high soil P

Irrigation

Variety Seeddensity Early

Seeding &high soil K

Low compaction

Early seeding

Crop rotation

High soil P0102030405060708090

% In

crea

se

YieldN use efficiency

Best management practices

(Corn results from several U.S. state’s)

$/ha0 100 200 300 400 500 600

Rel

ativ

eel

evat

ion

(m)

405

402

360

300

240

180

120

60

South to north

distance (m

)

060

120 180 240

West to east distance (m

)

Within-field returns fromoptimum N/P rates (Corn)

12 hectares, 1997Southwestern MNMalzer et al, U of MN