Phosphorus...

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Phosphorus... Essential for Life
Dr. Mark D. Stauffer President, Potash
Phosphate Institute of Canada Senior Vice
President, Potash Phosphate Institute
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Phosphates are a vital ingredient in the diets of
all living things
P

• 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

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Phosphorus is of universal importance to every
living cell
P
is incorporated into

• Nucleic acids (DNA, RNA, genes, chromosomes)
• Proteins
• Lipids
• Sugars
• Enzymes
• Energy rich P compounds (ATP, ADP)

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P
is critical to basic plant physiology

• Energy storage transfer for every biological
  process
• photosynthesis
• respiration
• cell division, development, enlargement, gene
  transfer, reproduction

Without phosphorus, there is no cell, no plant,
and no grain Without adequate phosphorus, there
is a lot of hunger
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P
Impact on crops

• Vigorous crop (Shoot/Root) growth
• Improved 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

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P
is mobile in the plantlinked to metabolic
processes is concentrated in the most active
areas of growth
(Jacobsen et al. 1992)
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Agronomic characteristics of P deficiency
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P
deficiency reflected in poor development at all
stages
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P
Impact on plant roots tillers (wheat)
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P
Impact on water use efficiency (wheat)
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P
Impact on nutrient use efficiency (wheat)
(Schwartz and Kafkafi)
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Impact on residual soil nitrate leaching
P
200
soil profile NO3-N after 30 years
150
without P
with P
100
Soil NO3-N in upper 3 m, kg/ha
At optimum N rate P reduced residual nitrate by
66
50
0
0
40
80
120
160
200
N rate, kg/ha
(Schlegel, Dhuyvetter, and Havlin, 1996)
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Impact on crop maturity (barley)
P
118
116
114
112
Site 1
Days to Maturity of Barley
110
Site 2
108
106
104
0
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27
40
P2O5 Rate, kg/ha
(Westco Alberta, Canada)
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Impact on yield cost of production
P
Schlegel, Dhuyvetter, and Havlin, 1996
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How much P is in the soil?

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

Soil Solution

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

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

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The Phosphorus Cycle
Plant uptake

• Soil solution
• phosphorus
• HPO4-2
• H2PO4-1

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Risk of environmental loss?
100
80
60
Relative crop yield,

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

40
20
0
Low
Medium
Sufficient
Soil Test P
(Sharpley et al. 1993)
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Phosphorus in the Watershed
Sharpley, Gburek, USDA-ARS Beegle, Penn State
University
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Soil Test P Distribution
Sharpley, Gburek, USDA-ARS Beegle, Penn State
University
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Vulnerability to P Loss
P loss vulnerability Low (clear) Medium High
Sharpley, Gburek, USDA-ARS Beegle, Penn State
University
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What Determines Phosphorus Fertilizer Need?
ƒ
Population, Land resources/fertility, Historic
nutrient use patterns, Cropping diversity, Export
versus domestic goals, Government policy, Current
Economy
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Indigenous Phosphorus supply - the net effect?
Highly P def soils
gt 60
40-60
20-40
(Fairhurst et al., 1999)
0-20
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Soybean yields US/Brazil
AgriStats, NASS
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Soybean growth US/Brazil
?
AgriStats, ANDA, NASS
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Soybean P removal US/Brazil
AgriStats
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• Opportunities
• World food demand
• Favorable climate
• Lower land price
• Low production cost
• High yields with fertility correction
• Improving infrastructure
• Political/economical stability

EC Joint Research Centre, 2002
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Smallholder farms - Sustainability of Slash
Burn Systems Oxisol, Manaus, Brazil

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

CROP
Rice Soybean Corn Cowpea
TREATMENT
N P K Lime Cu S B Zn Mn Mg
Year After Burning
Cravo and Smith, 1997
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• No fertilizer
• Total yield 1.73 t/ha

Cravo and Smith, 1997
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Soil fertility decay pattern No fertilizer
Cravo and Smith, 1997
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NPK plus Lime
Cravo and Smith, 1997
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Yield Response to P

• plus 3 t Aglime

Applied P kg/ha
396
264
132
Cumulative yield, t/ha
Control
Crop Number
Cravo and Smith, 1997
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Cerrado soil has poor fertility cant produce
without fertilizers
Gypsum LimePK 3,780 kg/ha
Seed only 480 kg/ha
Dirceu Broch, Fundação MS
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Grain production gaps
Compiled from Lopes, 1996 and Yamada, 2003
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Soybean P response in Cerrado soil
Source Fundação MT
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TOP FARMER GROUPS TO DEVELOP AND TRANSFER
TECHNOLOGY
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(No Transcript)
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Challenges

• Potential for agricultural expansion is great

• Projections for future production are bold

• How sustainable is this production?

• Maximum economic yield is always the desired
  goal

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

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P consumption world comparisons (kg per arable
ha)
AgriStats
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Soybean growth US/Brazil
AgriStats, ANDA, NASS
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Best management practices
90
80
Yield
70
60
Increase
50
40
30
20
10
0

(Corn results from several U.S. states)
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Within-field returns fromoptimum N/P rates (Corn)
12 hectares, 1997 Southwestern MN Malzer et al, U
of MN