Transcript Document

Fertilizer Use
Efficiency:
the North American
Experience
IFA Agriculture Committee
Fertilizer Demand Meeting
Philadelphia, PA
May 26, 2003
David W. Dibb, Paul E. Fixen,
and Mark D. Stauffer
Potash & Phosphate Institute/Potash & Phosphate Institute of Canada
Fertilizer Use Efficiency:
An Old Topic but With New Importance
 International Nitrogen Initiative (INI)
 Goal: to optimize N’s beneficial role in sustainable food
production and minimize N’s negative effects on human health
and the environment resulting from food and energy production.
 Will focus attention on improving fertilizer N efficiency at a global
scale
 Multiple Level Nutrient Management
 NRCS program under development to subsidize farmer practices
that improve nutrient use efficiency
 Will test our collective understanding of nutrient use efficiency for
N and P
Traditional Nutrient Efficiency Terms
 Recovery efficiency (RE) = Increase in
uptake per unit nutrient added usually expressed
as %
 Agronomic efficiency (AE) = Crop yield
increase per unit nutrient added such as
bu/lb or kg grain/kg nutrient
Kg grain per kg N .
Agronomic efficiency of fertilizer N used
on corn grain in the U.S., 1964-2002
75
70
65
60
55
50
45
40
35
30
59
43
1960 1965 1970 1975 1980 1985 1990 1995 2000
Since 1975:
39% increase in N efficiency
12% increase in fertilizer N per ha
40% increase in corn yields
N fertilizer recovery efficiency using
on-farm measurements
Opportunity for improvement
Crop
Region
Number
of farms
Avg N
rate,
kg/ha
Recovery,
%
Maize
NC USA
56
103
37
Rice
Asia-farmer
Asia-researcher
179
179
Wheat
India-poor weather
India-good weather
23
21
Cassman et al., 2002
117
112
145
123
31
40
18
49
Areas of opportunity for improvement
in fertilizer N efficiency
 Continued improvement in cropping
system management
 Realistic
estimation of attainable yield
 Yield potential protection – pest management
and other cultural practices
 Balanced nutrition
Balanced nutrition in the U.S.
 Ohio State University – dryland corn
 80
ppm soil test K
 139 ppm soil test K
45% N recovery
80% N recovery
 Kansas State University – irrigated corn
 No
P applied
 45 kg ha-1
35% N recovery
75% N recovery
Balanced nutrition in China
Treatment
Reference
Crop
N
NPK
N recovery by crop,%
Zhu, 1994
Barley
28
51
Jin, 2001
Wheat (11 yrs)
31
70
Corn (5 yrs)
35
66
Areas of opportunity for improvement
in fertilizer N efficiency
 Continued improvement in cropping
system management
 Use of site-specific precision ag
technologies
Site Specific Management:
Accounting for spatial variability
Spatial variability in fertilizer N efficiency
Year 1
Uniform N rate
11.1 t/ha average yield
Soybeans
In year 2
Indiana; two
N rates based
on soil type
N Efficiency,
kg grain/kg N
28-39
39-50
50-62
62-73
Murrell and Murrell, 2002
Year 3
Variable N rate
11.3 t/ha average yield
Variable N rate contributed to increased N
efficiency
40 ha field divided into 10 zones
Frequency of zones
9
Whole field year 1,
8
8
47 kg grain/kg N
Variable rate year 3, 53 kg grain/kg N
13% increase in
fertilizer N efficiency
7
6
5
4
4
3
2
2
2
1
2
1
1
0
0
28-39
39-50
50-62
62-73
N use efficiency, kg grain/kg applied N
Murrell and Murrell, 2002
Areas of opportunity for improvement
in fertilizer N efficiency
 Continued improvement in cropping system
management
 Use of site-specific precision ag technologies
 Better prediction of soil N mineralization
 Improved timing of N application
 Improved manure management and crediting
 Improved fertilizers
 Biotechnology?
Is the concept of fertilizer use
efficiency the same for P and K as it
is with N?
The result of applying the definition of
agronomic efficiency for N to P
 The highest “efficiency” occurs when inadequate amounts
are applied at low soil test levels
 Building soil test levels to optimum reduces “efficiency”
 “Efficient” P use means reduced profitability, water use
efficiency, N use efficiency, and land use efficiency
*
100
80
100
60
90
Relative yield, % .
P use efficiency, kg corn/kg P
120
40
20
**
0
5
10
15
Bray P-1, ppm
20
25
**
80
70
60
*
50
Low
Soil test level
High
We need to view P and K efficiency
as different than N efficiency
 A.E. Johnston and P Poulton
“The difference method (RE) is appropriate for N … but
is less useful for P and K where plant available
reserves of these nutrients can accumulate in the soil
from past applications of fertilizer.”
 Sustainable efficiency (for P&K) – Nutrient
input needed to sustain the system at optimum
productivity expressed as a removal to use ratio
P and K Sustainable Efficiency in N. America

Review current crop removal to use ratios
 Review current soil test levels
 Combine the two to assess efficiency
Information Sources:
• Soil Test Levels in North America, PPI/PPIC/FAR Technical Bulletin
2001-1.
• Plant Nutrient Use in North American Agriculture, PPI/PPIC/FAR
Technical Bulletin 2002-1.
Partial K budgets for the U.S.
(average of 1998-2000)
Region
Crop
Applied
Recov.
removal
fertilizer
manure*
Removal to use
fertilizer
fert+man
------- K2O, billion kg -----U.S.
8.8
4.6
1.7
1.91
1.39
6 corn states
3.0
1.9
0.5
1.62
1.30
* USDA-NRCS, 2000; Due to manure distribution problems relative to crop demand,
this likely overestimates the agronomic contribution.
Ratio of K removal by crops to fertilizer
applied plus recoverable manure
BC
AB
MB
SK
ON
PQ
WA
PEI
NB
ME
MT
ND
NS
MN
OR
VT
ID
WI
SD
NH
NY
MI
MA
CT
WY
IA
PA
NE
NV
IL
IN
KY
NC
AZ
DE
VA
MO
KS
TN
OK
NM
AR
SC
MS
TX
AL
> 5.00
MD
WV
CO
CA
0.00-0.89
0.90-1.09
1.10-1.49
1.50-4.99
NJ
OH
UT
RI
R/(F+M)
GA
LA
FL
Percent of Soils Testing Medium or Lower
in K in 2001
North America
43%
Partial P budgets for the U.S.
(average of 1998-2000)
Region
Crop
Applied
Recov.
removal
fertilizer
manure*
Removal to use
fertilizer
fert+man
------- P2O5, billion kg -----U.S.
5.2
4.0
1.5
1.30
0.95
6 corn states
2.3
1.4
0.4
1.71
1.33
*USDA-NRCS, 2000; Due to manure distribution problems relative to crop demand
and unavailability of a portion of manure P, this likely overestimates the agronomic
contribution.
Ratio of P removal by crops to fertilizer
applied plus recoverable manure
BC
AB
MB
SK
ON
PQ
PEI
WA
NB
ME
MT
ND
NS
MN
OR
ID
NH
NY
WI
SD
MI
MA
CT
WY
IA
PA
NE
NV
IL
IN
KY
NC
AZ
DE
VA
MO
KS
TN
OK
NM
AR
SC
MS
TX
AL
>1.50
MD
WV
CO
RI
0.00-0.49
0.50-0.89
0.90-1.09
1.10-1.49
NJ
OH
UT
CA
R/(F+M)
VT
GA
LA
FL
Percent of Soils Testing Medium or Lower
in P in 2001
North America
47%
Viewing removal to use in light of soil
test levels
 Large regional differences exist across North
America in both current removal to use ratios
and soil test levels
 “1” is often not the appropriate removal to use ratio
target for a state or for a field


Soil test levels < optimum: ratio should be < 1
Soil test levels > optimum: ratio should probably be > 1
 Starter fertilizer needs are often independent of
soil test levels or removal to use ratios
Est. crop removal / (fertilizer + manure use)
State level P assessment: R/(F+M)
1.8
1.6
1.4
Low and
decreasing
SD
IA
High but decreasing
WI
1.2
1.0
AR
0.8
0.6
0.4
0.2
GA
High and increasing
Low and increasing
0.0
-15
-10
-5
0
5
10
15
20
State median soil test level - target level, ppm
Target level = lower end of high category
25
Estimating target removal/use ratio for a field
 Target K test = 150 ppm




Current test = 130
Build: (150 - 130) x 9 kg K2O/ppm = 180 kg K2O/ha
To spread build over 4 yrs = 180/4 = 45 kg K2O/ha
Avg crop removal per year =
67 kg K2O/ha
Total to apply = 45 + 67 =
112 kg K2O/ha
Target removal to use ratio = 67/112 = 0.60
Examples of apparent recovery efficiency
of P fertilizer in long term studies
Soil(s)
Applied
No. of Recovery
P2O5, kg/ha Crops
%
Calcareous clay
67
5 F
28
Clay loam, pH 7.3
29
9 F
54
28 soils, pH 6.2-7.9
152
8 GH
74
4 soils, pH 6.7-7.6
230
19 GH
87
Sandy loam, non-calcareous
118
4 F
100
GH = Green house; F = Field.
Fixen, 1992
If a field is at its optimum soil test
level, and replacement of the P and
K removed by crops maintains that
optimum level, what is the efficiency
of P or K?
100%
If use must exceed removal to maintain optimum productivity,
soil erosion or fixation are often the cause:
 Reduce erosion losses
 Utilize banding and annual fertilizer application
Impact of Improving Efficiency on
Fertilizer Demand
 Critical to properly define efficiency for the
nutrient in question
 Nitrogen




Good progress has been made in improving
agronomic efficiency
Will be significant pressure to further improve
agronomic efficiency without sacrificing yield potential
Research shows there is room for improvement
Yields will likely continue to increase faster than N
use
Impact of Improving Efficiency on
Fertilizer Demand (continued)
 Phosphorus and potassium
 Will be increasing pressure to improve system efficiency
by reducing P levels where excessive
 Sustainable efficiency will translate into increased P and
K demand in some major production regions
 Pressure to improve N efficiency should result in
increased support for balanced nutrition with P and K
 Higher future crop yields could require higher target soil
test levels and temporarily impact demand
 The thermodynamic need to replace P and K removal at
some soil level sets a lower limit for P and K use
 As food needs increase … fundamentals of
natural systems indicate a permanent and
expanding role for fertilizers in food production