Phosphorus
• Phosphorus is critical for crop growth
– Structural component of nucleotides, nucleic acids and phospholipids.
– Essential for all energy reactions
– Needed for all growth processes
– Promotes root development, tillering, early flowering, seed production, and uniform ripening.
• P fertilizer is a major input for crop production on the Canadian prairies
• Low P recovery is a major economic and environmental concern
How Much Phosphorus is Needed by a Crop?
• A 45 bu/acre spring
wheat crop removes
about 24 lb P2O5 per
acre
– About 10 lb more taken up
but recycled in residue
– Total of about 34 lb needed
for growth
– 40 bu/acre canola removes
38 and needs around 58 lb
for growth
Without an adequate P supply,
crop yield will be reduced
-input and off-take should be
balanced over time to avoid
excess or depletion
-not all crop requirement has
to come from fertilizer in each
year
Plants Access P from Soil Solution
Soil solution
phosphorus
HPO4-2
H2PO4-2
Fertilizer additions make up
the difference between crop
demand and soil supply
Products and practices that attempt to improve
P use efficiency
• Banding P near the seed
• Use of more crop available forms
– Fluids versus dry
– Orthophosphates versus polyphosphates
• Reduce soil reactions
– Avail
• Release P gradually to match plant uptake
– Coated MAP
• Fungi that mobilize P in rhizosphere
– Provide Penicillium bilaii
• Fungi that improve plant access to P
– Mycorrhizae
5
How efficiently is P fertilizer used in wheat
systems on the Canadian prairies?
• It is estimated the P use efficiency in the year of application is generally less than 30%
• What happens to the other 70%? – Lost by run-off or erosion?
– Converted to other forms of varying solubility?
– Incorporated into the soil organic matter or microbial biomass?
– Used by subsequent crops?
• Can we use our P fertilizers more efficiently?
0
20,000
40,000
60,000
80,000
100,000
120,000
140,000
1965
1970
1975
1980
1985
1990
1995
2000
2005
P2O
5 (t
on
nes)
Source: Johnston 2006
P Added
P Removed
On a long-term basis, crop removal and replacement of P
seem to be relatively well-balanced
Indicates about 80%
recovery over time
Manitoba
1965-2006
Timing of supply is important for crop yield response
Phosphate
Fertilizer
Soil
Solution P
Mineral
Surfaces
Secondary
Ca and Mg or
Fe and Al
phosphates
Primary
Minerals
(Apatite)
Plant Uptake
Lower
Availability
Soil P Reactions Reduce P Availability
Principles of Phosphorus Nutrition that Affect
Fertilizer Management Choices
• Soil will supply P to the crop – Fertilizer “tops up” soil supply for optimum yield
– P availability varies with environmental conditions
• P is needed early in growth – Plants must have adequate supply in first 3-6 weeks
– Soil supply may be too low early in the season
– Need to apply starter at or before seeding
• P is not very mobile – Ties up with Ca, Mg, Al and Fe
– Doesn’t move far in the soil
– Roots must intercept P since P won’t move to roots
Phosphorus is Relatively Immobile in the Soil
Has important effect
on P management
decisions
Phosphorus Should be Banded
• Banding slows tie-up of P in soil – Having ammonium N in the band slows reactions further
– MAP, DAP and APP are effective P sources because they
contain ammonium
• Adding urea to MAP bands increases fertilizer P
uptake when fertilizer is banded away from seed
– However, excess N can delay P uptake due to band toxicity
Phosphorus Should be Banded
• Some plant roots proliferate in bands
• Ammonium in the band may also increase root
proliferation
• Uptake increases with P concentration and
rooting – Fertilizer bands provide high concentration
– More roots in the band increase uptake
Banding P Near the Seed-Row Ensures that Roots Will
Contact the P Granule Early in Growth
Broadcast Banded
At 25 Kg P2O5/Ha and 18 cm row
spacing have a granule every 2.3
cm (11-55-0)
The large difference between banded and broadcast
applications is POSITION
Courtesy Geza Racz
Banding P Near Seed is Most Important With
• Low soil P levels
• Restricted rooting
– Compaction
– Tillage pans
• Cool soil conditions – Solubility, mobility, rooting
– Early seeding
Fall band 70-30-10-10 on whole field
+10 lb/ac Seed
row P2O5
Pop-Up Effect from Seed Row P
Photo: Aaron Baldwin, Cargill
No starter P
Banding Reduces the Rate of P Needed
1.0
1.5
2.0
2.5
3.0
Gra
in Y
ield
(T/h
a)
0 10 20 40 80
Phosphate (kg/ha)
Broadcast
Banded
Westco Training Manual
20 band was as good
as 80 broadcast
Low P Mobility Limits How Much You Can Reduce P
Application Rates
• Must have a high enough rate that each
seedling can reach granule (or droplet)
during early growth
• Reducing rate below about 15-20 lb/acre
may restrict availability
• Distribution is affected by row spacing and
band width
– Greater the seed-bed utilization, the wider
apart the granules are spaced
– May need higher rate with higher seed-bed
utilization
Wheat - 7” rows, 5 lb/a P2O5
10 lb/a MAP fertilizer
7.6” between MAP particles
Wheat - 7” rows, 10 lb/a P2O5
19 lb/a MAP fertilizer
3.8” between MAP particles
Dry Fertilizer Material
Wheat - 7” rows, 15 lb/a P2O5
29 lb/a MAP fertilizer
2.5” between MAP particles
Wheat - 7” rows, 20 lb/a P2O5
38 lb/a MAP fertilizer
1.9” between MAP particles
Dry Fertilizer Material
Wheat – 7” rows, 5 lb/a P2O5
1.25 gallons/acre 10-34-0
11.2” between drops of fertilizer
Wheat – 7” rows, 10 lb/a P2O5
2.5 gallons/acre 10-34-0
5.9” between drops of fertilizer
Liquid Fertilizer Material
Wheat – 7” rows, 15 lb/a P2O5
3.75 gallons/acre 10-34-0
3.7” between drops of fertilizer
Wheat – 7” rows, 20 lb/a P2O5
5.0 gallons/acre 10-34-0
2.8” between drops of fertilizer
Liquid Fertilizer Material
Can different formulations improve P
availability?
• Monoammonium phosphate is the standard fertilizer source for the prairies
– Ammonium in formulation enhances efficiency
• Ammonium polyphosphate is standard fluid form
• Other novel formulations include:
– Fluid orthophosphates such as Alpine
– Avail additive
– Polymer coated MAP
Fluids Versus Dry
• Under highly calcareous conditions in
Australia, fluid forms of P are more available
than dry
– Water moving toward granule carries Ca
– Ca precipitates P and leads to small reaction
zone
– Fluid forms increase reaction zone and allow
greater root uptake
• Similar benefit has not shown up in tests in
Manitoba
There was no difference between dry MAP and fluid APP in
wheat yield over three years at two sites near Brandon
• Similar results in
previous studies by
Racz and in later
studies on wheat and
soybean
• Soils are much less
calcareous than the
70% calcium carbonate
in the Australian trials
Orthophosphates versus Polyphosphates
• Polyphosphates are chains of orthophosphates
• Most polyphosphate fertilizers still have 40-60% of the phosphate in the orthophosphate form
• Polyphosphate converts to orthophosphate in soils rapidly
– Half usually is converted within a week,
– Conversion may be slower if soils are cool and dry
• Generally no difference in effectiveness under field conditions
– http://www.extension.umn.edu/distribution/
cropsystems/DC6288.html
In studies by Tom Jensen at Brandon, 10-34-0 and MAP performed
as well or better than enhanced P products (Average of 8, 16 and 32
kg ha-1 phosphate rates)
41.2
39.2
38.2 38.1
37.2
35.7
38.5
38.0
32
33
34
35
36
37
38
39
40
41
42
Grain
yie
ld, b
u/a
cre
10-34-0 Simplot 7-
25-6-4
MAP or 11-
52-0
Omex 10-34-
0 plus TPA
Alpine 6-22-4 Alpine 6-24-6 AVAIL No AVAIL
a
b
ns
Some Enhanced Efficiency P Fertilizers Being Evaluated
• Avail – Maleic Itaconic Copolymer
– Similar technology to Nutrisphere
– Complexes Ca, Mg, Fe and Al
– Reduces fixation of P
– Limited data under prairie conditions
In studies by Tom Jensen at Brandon, yield was similar with MAP
alone or treated with Avail
41.2
39.2
38.2 38.1
37.2
35.7
38.5
38.0
32
33
34
35
36
37
38
39
40
41
42
Grain
yie
ld, b
u/a
cre
10-34-0 Simplot 7-
25-6-4
MAP or 11-
52-0
Omex 10-34-
0 plus TPA
Alpine 6-22-4 Alpine 6-24-6 AVAIL No AVAIL
a
b
ns
Wheat (6 site-years)
- Avail
+ Avail
22
24
26
28
30
32
34
0 10 20 30 40
Phophorus rate, lb P2O5/acre
Gra
in y
ield
, b
u/a
cre
Karamanos
In wheat on the prairies, yield was similar if
MAP was applied with or without Avail
Application of Avail-treated MAP produced the same
potato yield as side-banded MAP
f
e
abc ab
bc de
Gaia Consulting
Portage and Carberry 2007 to 2009
350
360
370
380
390
400
410
420
Pota
to Y
ield
(cw
t/acr
e)
Control
Sideband 20
Sideband 40
Sideband 80
Avail 40
Broadcast 40
Avail did not improve grain yield over MAP over three years at
two sites near Brandon
• No difference among
treatments
• All products performed
the same if banded
Coated Enhanced Efficiency P Fertilizer is Being Evaluated
• Polymer coated monoammonium phosphate – Same technology as ESN
– MAP is gradually released into soil solution
– Matching release to crop uptake should reduce fixation
– Can also reduce risk of seedling damage
– Limited testing so far
Neither the coated MAP nor the Avail improved grain yield over
MAP or APP over three years at two sites near Brandon
• No difference among
treatments
• All products performed
the same if banded
Novel formulations have not shown yield
benefit in most independent studies
• Fluids, MAP, orthophosphate and polyphosphates,
Avail-treated and coated products performs similarly
• Important to band an adequate amount near seed-row
• Ensure P is available early in the growing season
• Balance P rate with removal over time to avoid
depletion
34
What about the microbial products
• Two major products sold in western Canada
• Provide (Jumpstart and part of Tagteam)
• Mycorrhizal inoculants
35
Provide is a microbial inoculant
• Penicillium bilaii (also classified as P. bilaji and P.
bilaiae) is a fungi that colonizes the rhizosphere
• Effective in solubilizing phosphorus (P) under
controlled conditions
• Under field conditions, results have been mixed
36
On P responsive sites with durum wheat, Provide did not increase yield as
compared to the untreated control at nine site-years in Manitoba and Alberta
• Adding Provide alone was
equal to the untreated
control
• Adding Provide plus 10 lb
of phosphate gave yield
response of about ½ of
applying 20 lb of
phosphate
• Significant yield increase
with P but no significant
benefit of provide
20
30
40
50
60
Gra
in Y
ield
(bu
acre
-1)
Mean Minnedosa
Control
Provide aloneProvide + 10 lb P
20 lb P40 lb P
Grant et al. (2002)
Flax Yield Did Not Respond to Either Side-banded P
or Provide in Nine Site-Years in Manitoba
0
5
10
15
20
25
30
35
Gra
in Y
ield
(bu
acre
-1)
Brandon Minnedosa Rosebank
Control
20 P
Provide
Effect of P. bilaii and P fertilizer on wheat and barley
barley grain yield
60
80
100
120
140
160
0 9 18 27
P Rate (kg/ha)
Barl
ey Y
ield
(B
u/a
cre
)
P alone
P + P.bilaii
Karamanos
35
40
45
50
55
60
0 9 18 27
P Rate (kg/ha)
Wh
ea
t Y
ield
(B
u/a
cre
)
P alone
P + P.bilaii
47 site years – 20 site years
Mycorrhizal Association May Improve P Availability
• Mycorrhizae are an association between plant roots and a fungus – Especially important for flax and corn
– Do not occur with canola or sugar beet
– Mycelium grows into the soil and increases area mined for nutrients
• Fungi gives nutrients to plant and plant gives sugars to the fungi
• Mycorrhizae are reduced by: – Tillage
– Summer fallow
– P fertilization
– Following a nonmycorrhizal crop
Plant Root
Benefit of Inoculation with Mycorrhizae Uncertain
• Inoculation with mycorrhizae not widely tested in field conditions
• Native mycorrhizae exist naturally in soils
– Inoculation may not be needed under many conditions
• Some crops are more dependant on mycorrhizae
– Flax or corn versus wheat
• Crop “pays” mycorrhizae with photosynthate – If cost is greater than benefit, AM may decrease
yield
In nine site-years in Manitoba and Alberta colonization in
wheat roots was increased by inoculation and reduced by P
0
5
10
15
20
25
30
-Co
lon
iza
tio
n-
%
Lacombe MCDC Maziers
P Fertilizer
Control
Myc
*
*
*
0.0
0.4
0.8
1.2
1.6
Bio
ma
ss Y
ield
(T
ha
-2)
Lacombe MCDC Maziers
Control
P Alone
Mycorrhiza
Mycorrhiza + P
**
Biomass at Six Weeks Tended to Decrease
with Mycorrhizal Inoculant
Biomass yield at heading also tended to decrease
with inoculation
*
Mycorrhizal Inoculation Did Not Affect Wheat Grain
Yield in Nine Site Years in Manitoba and Alberta
Inoculant tended to reduce grain yield at Philips in 2005
10
15
20
25
Gra
in Y
ield
(bu
acre
-1)
Control
MAP S
B
CRP SB
APP SB
APP Drib
.
No Myc. Myc
• Yield was higher with P
fertilizer than inoculant
alone
• Grain yield was reduced
at Philips when
inoculant was added
with fertilizer
Effect of mycorrhizal inoculation
• Mycorrhizal inoculation increased colonization – Tended to decrease early biomass
production
– No benefit on final grain yield
– Sometimes led to a small decrease in yield
• Mycorrhizae may “cost” wheat more than they contribute
• Need more information on other crops
– Effect may differ with flax
Summary
• P use efficiency in the year of application can be low
– 25 to 30%
• P reacts in the soil to forms that are less available than
original fertilizer
– However plants can still access this P in following years
48
Summary
• Banding starter P placed close to the seed is important
to optimize crop yield
• Cutting rate too low may not place P close to each seed
• Little difference between MAP and other new
formulations under Manitoba conditions
– Fluids vs dry
– Orthophosphates vs polyphosphates
– Avail treatments
– Polymer coating
49
Summary
• Provide does not appear to be highly beneficial under
field conditions
• Inoculation with mycorrhizal spores can increase
colonization in wheat
– Does not lead to yield increase
– May decrease yield under some conditions
• Inoculation needs more testing with mycorrhizal-
dependent crops like flax
50
Summary
• Crop removal of P is fairly well balanced with P addition
in non-manured fields
• P use efficiency may be higher than we think
• Cutting application rates to less than crop removal may
not be desirable
– Too little P for plant roots to physically access
– Long-term depletion of soil P
– Crop productivity is lower on P depleted soils
• Band an available form of P near the seed row at rates
that reflect crop removal over the cropping sequence
51
Thank You
For your
Attention