Phosphorus Nutrition of Canola

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Phosphorus Nutritionof Canola
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Outline P Nutrition of Canola

• 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?

Photo courtesy of Canola Council of Canada
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What Have the Trends Been in Canola Yield?
NASS Statistics Canada
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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

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What are the nutrient requirements of canola
throughout the season?
Photo courtesy of Canola Council of Canada
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Plants Take Up P As

• Primary orthophosphate ionH2PO4- (pH lt 7.0)
• Secondary orthophosphate ionHPO4 (pH gt 7.0)
• The form most common is a function of soil pH
  both equally present at neutral pH

Solution P
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How Much N, P, K, and S Does Canola Take Up
Johnston et al., 1999
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How Are Nutrients Distributed in Canola at
Harvest?
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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
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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
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P Deficient Canola - Symptoms?
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What Role Does FertilizerP Play in Canola Growth?
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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

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Response of Canola and Wheat to Fertilizer P
Strong and Soper, 1974
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Proportion of Fertilizer P Taken Up by Canola
Karla and Soper, 1968
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Impact of Fertilizer P Placement
Photo courtesy of Roley Rumbold
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Why is band placement of P near the seed
important?
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The primary cause of low short-term uptake of P
fertilizer is

• The inability of P to move to absorbing roots
• SolutionRoots adapt and respond through
  increased development when they encounter sources
  of soil and fertilizer P

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Plant Root Growth in P Band Reaction Zone

• 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

Strong and Soper, 1974
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P Placement Can Influence Crop Response
Spring broadcast, 40 lb P2O5/A
Seed-placed, 20 lb P2O5/A
Agrium
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Effect of Seed Row P (as MAP) on Canola
Emergence and Yield
10 seed bed utilization
Nyborg and Hennig, 1969
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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

75 lb N/A 25 lb P2O5/A
Western Co-operative Fertilizers Ltd.
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What Is the Role of P in Balancing Canola
Nutrition?
Photo courtesy Neil Harker
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Nitrogen x Phosphorus Interactions
Lafond, 2003
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Hybrid Canola Response to N and P Rates
Karamanos, Unpublished data.
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Does P Fertilizer Form Influence Crop Response?

• 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

Fixen, 1989 Leikam, 1990
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Related Impact of P Nutrition in Canola

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

Photo courtesy of Canola Council of Canada
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How can I be sure P supplies are adequate?
Photos courtesy of the USDA NRCS
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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

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How Is A Soil Test Calibrated to Yield Response?
Nyborg, 1975
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Example of P Soil Test Calibration Data

• Calibration curve indicates which soil test
  levels tend to limit yields
• Data based on P responses observed across several
  sites and years

McKenzie et al., 1995
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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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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

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What are some good strategies for managing P?
Photos courtesy of the USDA NRCS
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Approaches to P Fertilization

• Sufficiency approachApply 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

Relative yield,
Soil test P level
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Approaches to P Fertilization

• Build and maintenanceapproachRemove 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

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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

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International Plant Nutrition Institute
(IPNI)655 Engineering Drive, Suite 110Norcross,
GA 30092-2604Phone [phone] Fax
770-448-0439www.ipni.net
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