Phosphorus Nutrition
Of Corn
Outline –
P Nutrition of Corn
•
•
•
•
•
•
Changes in root system development over the season
Impacts on attainable yield potential
Requirements through growth stages
Placement options
Soil test levels and corn response to P inputs
Profitability of P fertility management
Corn Root System
Development
36 Days
8 Weeks
Mature
Source: Weaver, 1926
The first roots grow from the
seed, but the main root
system starts from the first
node above the seed.
Planting depth affects the
depth of the seed roots, but
the depth of the initiation of
the main root system is the
same, regardless of
planting depth.
Mycorrhizae
• “Fungus-root”
• Extend to absorb P from more soil
• Decline with increasing P fertility, fallow
Effect of fertilizer P on corn mycorrhizae.
Fertilizer P2O5
Rate, lb/A
Roots colonized at
6-leaf stage
Corn dry matter at
silking, tons/A
0
21%
4.5
55
19%
5.0
110
15%
5.2
Mean of 2 years, 1997/98, Quebec. Soil test P (Mehlich 3) was
65 to 87 ppm. Adapted from Liu et al., 2002
Early P Nutrition –
Outdoor Hydroponics
P supplied
Shoot P @
V1
Shoot P @
V3-V4
Kernel,
Yield,
up to V3-V4
%
%
#/plant
bu/A
High
0.58
0.72
444
155
Medium
0.52
0.44
410
138
Low
0.49
0.28
398
134
All treatments received high P after V3-V4 (ISU)
Mean of 2 years, 1985-1986
Source: Barry & Miller, 1989
How a Corn Plant Takes Up
Phosphorus
High-yield corn (307 bu/A)
Source: Karlen et al., 1988.
Nutrient Uptake in Corn
Versus Stage of Growth
Silt loam soil;
planted May 5,
1971; final grain
yield 187 bu/A.
Total P2O5 uptake, lb/A
Corn grown in silt
loam at Purdue
Agronomy Farm,
Indiana.
75%
Silking
90
80
70
60
50
Maturity
Maximum uptake rate
2 lb/A/day @ 45 dap
40
30
20
10
0
0
15
30
45
60
75
90
Days after planting
Source: Mengel & Barber, 1974
105
120
135
Nutrient Uptake:
• Total uptake ~0.55 lb P2O5
per bushel of grain yield
• Silage harvest removes 3.2 - 4.8 lb
P2O5 per ton at 65% moisture
Nutrient Removal in Grain:
0.34 - 0.44 lb of P2O5 per bushel
Source: Heckman et al., 2001
P Deficiency in Corn
Seedlings
Why Broadcast?
•
•
•
•
Can apply large amounts conveniently
Ideal for building soil fertility
Minimizes risk of fertilizer injury
On fields of low fertility, banded starter P may not be
adequate for maximum yield
• Combinations of broadcast and band applications
produce the highest yields on low testing soils
Band Application
• Overwhelms soil fixation capacity
• Places nutrients near the seedling
– Roots intercept early and proliferate near the band
– Including ammonium-N, slows P fixation and lowers pH near
the root to improve both P and micronutrient availability
• Favors the crop over the weeds
• Keeps nutrients away from the surface
– Reduces runoff P concentrations
Placement Options
Tillage
One-pass
Strip-till
Source: Randall, et al., 2001
P
P2O5 applied,
Grain yield, bu/A
application
lb/A
1997-2000 average
method
High P site
Low P site
High P site
Low P site
None
0
0
168
104
Starter
40
50
171
153
Broadcast
80
100
174
164
Fall band
40
50
164
144
None
0
0
164
103
Starter
40
50
169
151
Fall Band
40
50
167
143
Fertility Affects Impact of
P and K Placement
Low fertility
Placement
Fall chisel
Ridgetill
High fertility
Fall chisel Ridge-till
——— Two-year average, bu/A ———
Control
84
87
156
150
Broadcast
110
102
151
151
Surface band
108
112
152
152
Deep band
118
123
153
153
Source: G.W. Rehm, Minnesota
Placing P With the Seed
• Ontario research from 1960s and 1970s (52 site-years)
showed that 6-24-6 @ 50 lb/A with the seed:
–
–
–
–
Increased yield by zero to 2.9%
Delayed and sometimes reduced emergence
Hastened time to silking
Decreased grain moisture at harvest
Source: Bates, 1971; Richards, et al., 1985
Seed Placement:
Small Amounts, Liquid
or Granular
1
P2O5 rate,
Corn yield,1
lb/A
bu/A
0
137
Rate,
lb P2O5/A
5
151
10
21
Liquid3
Granular
MAP,
13-52-0
0
145
145
146
10
156
156
148
21
152
157
Mean of two hybrids at each of
two Ontario sites; seed-placed
8-19-3
Source: Lauzon et al., 1995
Corn yield,2 bu/A
2
Mean of three Ontario sites
3 Mean of three products:
10-34-0, 6-24-6, 8-19-3
Late Planting of Full
Season Corn Increased
Response to Starter in
Wisconsin
Source: Bundy, 2001
P Sources and Solution pH
Symbol
Compound
Formula
pH
TSP
monocalcium
phosphate
Ca(H2PO4)2
1.5
MAP
monoammonium
phosphate
NH4H2PO4
3.5
TPP1
triammonium
pyrophosphate
(NH4)3HP2O7
6.0
DAP
diammonium
phosphate
(NH4)2HPO4
8.0
1
Main P form in liquid 10-34-0
Soil Test Interpretation:
Index of the Likelihood of
Crop Response
Soil test
category
Very low
Low
Medium
High
Very high
Probability of response to P
MN-SD-ND
> 80%
60-80%
40-60%
20-40%
< 20%
Category definitions vary among laboratories
ON
75%
55%
25%
< 25%
Corn Response to P
100
Relative Yield, %
90
80
Iowa
Illinois
Missouri
70
60
50
40
30
0
5
10
15
20
25
Soil Test P, ppm [Bray P1]
Source: PKMAN Version 1.0, PPI
30
35
40
Bray P-1 (ppm)
Mining P Reduces Soil
Test P
50
45
40
35
30
25
20
15
10
5
0
298 lb P2O5 in 1975
0 lb P2O5 in 1975
Data source: Webb et al., 1992 (Iowa)
Residual Effect of P
Corn grain yield, bu/A
200
298 lb P2O5 in 1975
175
150
125
100
75
50
Data source: Webb et al., 1992 (Iowa)
0 lb P2O5 in 1975
Phosphorus and Zinc
P2O5
Zn
lb/A *
• Zn deficiency impairs
plant P regulation
• Either high soil P or
large amounts of
applied P can induce
Zn deficiency if soil Zn
is low and no Zn
fertilizer is applied
Data source: Adriano and Murphy
Yield
Leaf tissue
bu/A
P, %
Zn, ppm
0
0
101
0.14
12
0
10
102
0.16
24
80
0
73
0.73
10
80
10
162
0.41
17
* P and Zn band-applied
Phosphorus and Zinc
• Continuous application of very high rates of P does not
always induce greater Zn deficiency (Mallarino, 1995)
Olsen soil test
P, ppm
Adapted from Shang & Bates, 1987
Fertilizer P2O5
applied, lb/A
Corn seedling
Zn, ppm
10
18
60
8
115
21
915
18
Effect of N and P on
Corn Yield
200
with P
without P
Yield, bu/A
180
N rate at MEY:
with P = 159 lb/A
without P = 145
160
140
P increased N use
efficiency instead
of greatly
increasing N
fertilizer demand
120
100
80
60
0
20
40
60
80
100 120 140 160 180 200
N rate, lb/A
Source: Schlegel et al., 1996
Irrigated continuous
corn, Kansas, 30 years
data, 1961-1991.
Effect of N and P on
Net Revenue
200
with P
without P
Net revenue, $/A
150
100
The economic optimum
N rate with P is 159 lb/A.
50
P increased profit by
about $120/A at this rate
0
0
20
40
60
80
100
120 140
160 180
200
-50
-100
N rate, lb/A
Source: Schlegel et al., 1996, 30 year average
Corn $2.30/bu, N $0.15/lb,
P2O5 $0.24/lb;
other costs $240/A
P Reduces Residual Soil
Nitrate and Potential for
Nitrate Leaching After
30 Years
Soil NO3-N in upper 10 ft, lb/A
200
with P
without P
150
At optimum N rate,
P reduced residual
nitrate by 66%
100
50
0
0
40
80
120
N rate, lb/A
Source: Schlegel et al., 1996; 30 year average
160
200
Phosphorus Hastens Corn
Maturity
Phosphorus Hastens Maturity
and Lowers Drying Costs,
Adding to Return to P
Net return to 40 lb P 2O 5 /A, $/A
250
200
Drying cost reduction
Yield response income
150
100
50
0
0
40
80
120
160
200
Fertilizer nitrogen rate, lb/A
Calculated from Dhuyvetter
and Schlegel. 1994.
Corn, $2.50/bu; N, $0.15/lb;
P2O5, $0.24/lb
Summary P Nutrition of Corn
•
•
•
•
•
•
Roots must grow to where the P is, since P is nearly
immobile in most soils
Seedlings provided with high P develop higher
attainable yield potential
Uptake of P continues through the season
Placement near the seedling often boosts yield.
Corn response to P depends on soil test level
P fertility management is key to profitability and
efficient use of N
International Plant Nutrition Institute (IPNI)
655 Engineering Drive, Suite 110
Norcross, GA 30092-2604
Phone: 770-447-0335; Fax: 770-448-0439
www.ipni.net
Reference 06128