Are We Managing for Higher Yields?
Should We Strive for Higher Yields Symposium
American Society of Agronomy Annual Meeting
November 11, 2002
Indianapolis, IN
Paul Fixen
Potash & Phosphate Institute
pfixen@ppi-far.org
Web: www.ppi-ppic.org
Yield trends in the U.S.
150
130
Yield (bu/A)
120
50
Corn
1.9 bu/A/yr
45
y = 1.87x - 3610
40
Yield (bu/A)
140
110
100
90
80
30
25
We are managing
for higher yields
10
50
1965
1970
1975
1980
1985
1990
1995
1960
2000
3.8
1965
1970
1975
1980
1985
1990
1995
2000
1995
2000
50
Alfalfa
52 lb/A/yr
y = 0.0262x - 48.86
45
40
Yield (bu/A)
Yield (tons/A)
35
15
60
3.4
y = 0.407x - 773
20
70
1960
Wheat
0.41 bu/A/yr
3.0
2.6
Soybeans
0.38 bu/A/yr
y = 0.3794x - 720.97
35
30
25
20
2.2
15
10
1.8
1960
1965
1970
1975
1980
1985
1990
1995
2000
1960
1965
1970
1975
1980
1985
1990
Are we managing for attainable yields?
• What yields are attainable?
• A site-specific question
• Highest research yields
• Farmer examples – rain fed corn in IA and IL
• What management practices were used to
get them?
• Does not tell us what was required
• Does offer research direction
• What practices are currently being used?
Top corn yields from researchers in 1982
Dr. Roy Flannery
New Jersey
Dr. Sterling Olsen
Colorado
338 bu/A
332 bu/A
Exploitable yield potential in corn
450
H. Warsaw
Saybrook, IL
Corn yield, bu/A
400
F. Childs
Manchester, IA
350
300
1965-1991
2.0 bu/A/yr
250
1992-2001
20.1 bu/A/yr
IA Contest Winners
200
A yield gap does exist
150
100
IA State Average
50
1.6 bu/A/yr
0
1965
1970
1975
1980
1985
Year
1990
1995
2000
Herman Warsaw yield history, 1966-1985
400
Saybrook, IL
Corn yield, bu/A
350
300
250
200
7.4 bu/A/yr
150
100
1965
1970
1975
Year
1980
1985
Rain fed corn yields & rainfall - Herman Warsaw
Saybrook, IL
15-year
average
274 bu/A
Variable rainfall
From Saybrook, IL to Manchester, IA: Climate
Manchester, IA
Growing season climate, 1971-2000
Precip
Temp
GDD
Month
Man Urbana Man Urbana Man Urbana
Inches
Apr
May
Jun
Jul
Aug
Sep
Oct
Tot/Avg
3.3
3.9
4.6
4.4
5.0
3.3
2.6
27.0
3.7
4.8
4.2
4.7
4.4
3.2
2.8
27.7
F
47
59
68
72
70
61
50
61
51
62
72
75
73
66
54
65
Base 50
162 212
367 436
557 641
672 751
611 702
412 505
199 266
2980 3513
Source: Midwest Regional Climate Center
Saybrook, IL
From Saybrook, IL to Manchester, IA: Soils
Manchester, IA
Property
Soil type
Taxonomy
Cap. Class
Org. mat., %
pH
P1, ppm
K, ppm
Childs
Kenyon loam
Typic Hapludolls
IIe
5.5-6.0
5.3-6.1
126 (VH)
374 (VH)
Warsaw
Parr silt loam
Oxyaquic Argiudolls
5.3
6.0
81 (VH)
400 (VH)
Source: Childs data – Murrell and Childs, 2000; Smith, 2000; Dobermann, 2002
Warsaw data – PPI, 1986.
Saybrook, IL
From Saybrook, IL to Manchester, IA: Soil OM
Manchester, IA
Depth, In
Childs
0-6
6-12
12-18
18-24
24-30
30-36
5.6
4.5
3.0
-------
Warsaw-light Warsaw-dark
Organic matter, %
5.8
4.5
4.9
3.9
3.2
4.3
1.4
4.3
0.8
3.8
0.6
3.6
Source: Childs data – Dobermann, 2002.
Warsaw data – PPI, 1977.
Saybrook, IL
Fence row
5.2
3.7
2.7
2.3
1.5
0.9
From Saybrook, IL to Manchester, IA: Farmer
attributes
Manchester, IA
Dedicated to a concept … but very patient
• Warsaw: 20 years of intensively managed
continuous corn
• Childs:
35 years of intensively managed
continuous corn
Saybrook, IL
From Saybrook, IL to Manchester, IA: Practices
Manchester, IA
Practice
Fall tillage
Hybrid
Harv. Population
Row spacing
Manure
Childs
Mini MP 14” deep
Pioneer 34M95
34,000 - 40,000
30”
Historical high rates
Fall P2O5+K2O
180+120 (99, not 01)
Fall N, lb/A
50(UAN)
Preplant N
250(NH3 + sep. stab.)
Starter, N+P2O5+K2O
6+15+15
Postplant N
50(UAN)
3.5-4’ tall N
50(UAN+Guardian)
Fert N, lb/A
406 (1.0 bu/lb)
Other nutrients
Boron
Warsaw
CH 14” deep
FS 854
36,000
28”
20 T/A annually
250+250
45(DAP)
300(UAN)+ 100(AS)
26+26+26
75(UR)
None
546 (0.7 bu/lb)
Sulfur
Saybrook, IL
bu per lb of nutrient
Corn grain produced in the U.S. per unit of fertilizer
N used, 1964-2000.
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
1960
1.03
1970
1980
1990
2000
Questions about requirements:
Which practices are critical and at what level?
• Determination of site-specific attainable yield
estimates (Crop models)
• Carbon cycling – crop and environmental impacts
• Crop rotation vs monoculture
• Tillage requirements … no till/strip till
• Minimum N requirements, NH4+ vs NO3-, timing
• Role of subsoil fertility, organic matter, etc.
• Role of manure application
• Minimum soil test P and K requirements
• Role of secondary and micronutrients
• Importance of starter fertilizer (early yield
components)
Early Plant P status Impacts corn yield potential
(outdoor hydroponics study)
• P concentrations below 0.5% prior to V3V4 (ISU System), reduced kernels initiated
per ear and grain yield
• If kernel abortion is limited, final kernel
number should be correlated with kernels
initiated
• High early plant P concentrations should be
important for conserving yield potential in
high yielding environments
Barry & Miller, 1989
Seed is dominant P source
V2 - Soil becomes
dominant P source
Plant demand on
the soil for P
approaches
a maximum
P uptake per unit of root length (Barber, Purdue).
Plant P concentrations in Herman Warsaw’s corn
(Field 3W)
Year
Growth stage – plant part
1981 1982 1983 1984 1985
P,%
Seedling - whole plant
0.57
0.64
0.53
0.57
0.54
Early growth - 3rd leaf from top
0.39
0.35
0.31
0.39
0.39
Tasseling – earleaf
0.33
0.37
0.43
0.28
0.38
Sampled by Shields Soil Service, Saybrook, IL; Analysis by Agrico Labs.
• Theory (Barry and Miller; Barber) and practice (Warsaw) suggest starter P
might be important to obtain sufficient early plant P concentrations.
• Has not been demonstrated as essential for reaching attainable yields under
actual field conditions.
Soil Test P and K requirements for very high yields:
Classical theory
• For soil immobile nutrients like P or K, the STL vs % yield
relationship should not vary with site yield potential unless
plant population increases enough for adjacent roots to
compete for each other for P and K (Bray, 1954; Bray,
1963).
• Roots normally occupy less than 1% of soil volume (Barber,
1984) … an increase in size of the root system translates
into a greater volume of soil P or K being available for
uptake.
• As long as the size of the root system increases
proportionally with yield, a higher yielding crop should not
need a higher P or K concentration at the root surface …
should not require a higher soil test level.
Soil Test P and K requirements for very high yields:
Conditions that could lead to higher requirements
• Shoot growth increases that exceed root growth increases
as yields climb
• increasing N, P or available water (Barber, 1984)
• decreasing light intensity (Troughton, 1980; Horvath et
al., 1980)
• soil temperatures in the 75-85 F range (Walker, 1969;
Nye and Tinker, 1977)
• Redistribution of roots from the surface soil to a low P or K
subsoil
• soil factors (organic matter, pH, structure, etc.)
• varietal factors – vertical vs lateral rooting tendencies
• Each % increase in yield has greater economic value … want
to be further up the response curve
Repeated applications of P or K build profile soil
test levels
• Manure applied for 10 years
in this example
• The higher the surface
levels, the greater the
depth of high fertility
• A role that manure has
played in high yield
systems?
• If depth is critical, deep
placement may be an
alternative to extreme
surface level (Ongoing
Purdue study)
Data: Sharpley et al., 1984
Research needed
• “Research has given us good components
or parts … But greater strides toward high
yields will likely come through fitting those
parts into combinations that produce
positive interactions.”
Dr. Robert Wagner, 1979
Yield change due to
higher population, %
Impact of hybrid on the influence of N rate on yield
response to plant population in Colorado
12
8
4
320
0
-4
225
27K vs 38K
A
39K vs 46K
B
C
Variety
S.R. Olsen, reported by W. M. Stewart, 2000
D
150
lb N/A
Soil test P levels in the 6 leading corn states, 2001
Percent under 20 ppm Bray P1 equivalent
Indiana 25
Ohio 31
Illinois 16
Iowa 39
Minnesota 60
Nebraska 47
Soil test K levels in the 6 leading corn states, 2001
Percent under 160 ppm K
Indiana 71
Illinois 56
Minnesota 51
Ohio 56
Iowa 54
Nebraska 12
Phosphorus and potassium crop removal to nutrient
use ratios for the 6 leading corn producing states.
P
K
Ohio
Indiana
Illinois
Iowa
Minnesota
Nebraska
Ohio
Indiana
Illinois
Iowa
Minnesota
Nebraska
PPI, 2002.
1.32
1.53
1.60
2.03
1.72
1.87
1.07
1.24
1.44
1.47
1.25
1.33
1.19
1.02
1.00
0.89
1.04
0.96
1.77
1.33
2.24
1.62
12.39
3.44
Average of 1998-2000.
65
Medium or below, %
Nutrient State
Removal to use ratio
without
with
manure
manure
Medium or below in K: OH IN IL
60
55
50
45
40
1970
1975
1980
1985
1990
1995
2000
Are we managing for attainable yields?
• Probably not since typical yields are below what is likely
attainable
• To narrow the gap we need expanded research at high yield
levels
• Define site-specific attainable yields
• Management practices essential to attain them
• A mix of small plot multi-factor research and on-farm field scale
studies … linked with appropriate models
• Modern technologies should facilitate narrowing the gap
between attainable and typical yields
• “Calibrated” simulation models to help define attainable yields
• Improved weather data and management tools
• Site-specific technologies for greater efficiency
• Biotechnology for yield protection … and building
Are We Managing for Higher Yields?
Should We Strive for Higher Yields Symposium
American Society of Agronomy Annual Meeting
November 11, 2002
Indianapolis, IN
Paul Fixen
Potash & Phosphate Institute
pfixen@ppi-far.org
Web: www.ppi-ppic.org