Phosphorus NutritionOf 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

36 Days

8 Weeks

MatureSource: Weaver, 1926

Corn Root System Development

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.

Fertilizer P2O5

Rate, lb/ARoots colonized at

6-leaf stageCorn 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

Effect of fertilizer P on corn mycorrhizae.

Mycorrhizae

• “Fungus-root”• Extend to absorb P from more soil• Decline with increasing P fertility, fallow

P suppliedShoot P @

V1Shoot 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

Early P Nutrition – Outdoor Hydroponics

High-yield corn (307 bu/A)Source: Karlen et al., 1988.

How a Corn Plant Takes Up Phosphorus

Source: Mengel & Barber, 1974

Corn grown in silt loam at Purdue Agronomy Farm, Indiana.

Silt loam soil; planted May 5, 1971; final grain yield 187 bu/A.

Nutrient Uptake in Corn Versus Stage of Growth

0

10

20

30

40

50

60

70

80

90

0 15 30 45 60 75 90 105 120 135

Days after planting

To

tal

P2O

5 u

pta

ke,

lb/A

75% Silking

Maximum uptake rate2 lb/A/day @ 45 dap

Maturity

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

Source: Heckman et al., 2001

0.34 - 0.44 lb of P2O5 per bushel

Nutrient Removal in Grain:

P Deficiency in Corn Seedlings

• 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

Why Broadcast?

• 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

Band Application

P P2O5 applied, Grain yield, bu/A

application lb/A 1997-2000 average

Tillage method High P site Low P site High P site Low P site

One-pass None 0 0 168 104

Starter 40 50 171 153

Broadcast 80 100 174 164

Fall band 40 50 164 144

Strip-till None 0 0 164 103

Starter 40 50 169 151

Fall Band 40 50 167 143

Source: Randall, et al., 2001

Placement Options

Source: G.W. Rehm, Minnesota

Low fertility High fertility

Placement Fall chisel Ridge-

till 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

Fertility Affects Impact of P and K Placement

Source: Bates, 1971; Richards, et al., 1985

• 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

Placing P With the Seed

P2O5 rate, Corn yield,1

lb/A bu/A

0 137

5 151

10 146

21 148

1 Mean of two hybrids at each of two Ontario sites; seed-placed 8-19-3

2 Mean of three Ontario sites3 Mean of three products:

10-34-0, 6-24-6, 8-19-3

Corn yield,2 bu/A

Rate,lb P2O5/A

Liquid3

Granular MAP,

13-52-0

0 145 145

10 156 156

21 152 157

Source: Lauzon et al., 1995

Seed Placement: Small Amounts, Liquidor Granular

Source: Bundy, 2001

Late Planting of Full Season Corn Increased Response to Starter in Wisconsin

Symbol Compound Formula pH

TSP monocalcium Ca(H2PO4)2 1.5phosphate

MAP monoammonium NH4H2PO4 3.5phosphate

TPP1 triammonium (NH4)3HP2O7 6.0pyrophosphate

DAP diammonium (NH4)2HPO4 8.0phosphate

1 Main P form in liquid 10-34-0

P Sources and Solution pH

Soil test Probability of response to Pcategory MN-SD-ND ON Very low > 80%Low 60-80% 75%Medium 40-60% 55%High 20-40% 25%Very high < 20% < 25%

Category definitions vary among laboratories

Soil Test Interpretation: Index of the Likelihood of Crop Response

Source: PKMAN Version 1.0, PPI

30

40

50

60

70

80

90

100

0 5 10 15 20 25 30 35 40

Soil Test P, ppm [Bray P1]

Rel

ativ

e Y

ield

, %

Iowa

Illinois

Missouri

Corn Response to P

Data source: Webb et al., 1992 (Iowa)

Mining P Reduces Soil Test P

298 lb P2O5 in 1975

0 lb P2O5 in 19750

5

10

15

20

25

30

35

40

45

50

1975

1977

1979

1981

1983

1985

1987

1989

Bra

y P

-1 (

pp

m)

Data source: Webb et al., 1992 (Iowa)

Residual Effect of P

298 lb P2O5 in 1975

0 lb P2O5 in 1975

50

75

100

125

150

175

200

1976

1978

1980

1982

1984

1986

1988

Co

rn g

rain

yie

ld,

bu

/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

P2O5 Zn Yield Leaf tissue

lb/A * 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

Data source: Adriano and Murphy

* 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

Fertilizer P2O5 applied, lb/A

Corn seedling Zn, ppm

10 18

60 8

115 21

915 18

Adapted from Shang & Bates, 1987

Phosphorus and Zinc

Irrigated continuous corn, Kansas, 30 yearsdata, 1961-1991.

N rate at MEY:with P = 159 lb/Awithout P = 145

P increased N use efficiency instead of greatly increasing N fertilizer demand

Source: Schlegel et al., 1996

Effect of N and P onCorn Yield

60

80

100

120

140

160

180

200

0 20 40 60 80 100 120 140 160 180 200

N rate, lb/A

Yie

ld,

bu

/A

with P

without P

Source: Schlegel et al., 1996, 30 year average

Corn $2.30/bu, N $0.15/lb, P2O5 $0.24/lb; other costs $240/A

The economic optimum N rate with P is 159 lb/A.

P increased profit by about $120/A at this rate

Effect of N and P onNet Revenue

-100

-50

0

50

100

150

200

0 20 40 60 80 100 120 140 160 180 200

N rate, lb/A

Net

rev

enu

e, $

/A

with P

without P

Source: Schlegel et al., 1996; 30 year average

At optimum N rate, P reduced residual nitrate by 66%

P Reduces Residual Soil Nitrate and Potential for Nitrate Leaching After 30 Years

0

50

100

150

200

0 40 80 120 160 200

N rate, lb/A

So

il N

O3-

N i

n u

pp

er

10

ft,

lb

/A

with P

without P

Phosphorus Hastens Corn Maturity

Corn, $2.50/bu; N, $0.15/lb; P2O5, $0.24/lb

Calculated from Dhuyvetter and Schlegel. 1994.

Phosphorus Hastens Maturity and Lowers Drying Costs, Adding to Return to P

0

50

100

150

200

250

0 40 80 120 160 200

Fertilizer nitrogen rate, lb/A

Net

ret

urn

to

40

lb P

2O5/A

, $/

A Drying cost reductionYield response income

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 110Norcross, GA 30092-2604Phone: 770-447-0335; Fax: 770-448-0439www.ipni.net

Reference 06128