Fertilizer Use Efficiency: the North American Experience

1
Fertilizer Use Efficiencythe 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
2
Fertilizer Use Efficiency An Old Topic but With
New Importance

• International Nitrogen Initiative (INI)
• Goal to optimize Ns beneficial role in
  sustainable food production and minimize Ns
  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

3
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

4
Agronomic efficiency of fertilizer N used on corn
grain in the U.S., 1964-2002
59
43
39 increase in N efficiency 12 increase in
fertilizer N per ha 40 increase in corn yields
Since 1975
5
N fertilizer recovery efficiency using on-farm
measurements Opportunity for improvement
Cassman et al., 2002
6
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

7
Balanced nutrition in the U.S.

• Ohio State University dryland corn
• 80 ppm soil test K 45 N recovery
• 139 ppm soil test K 80 N recovery
• Kansas State University irrigated corn
• No P applied 35 N recovery
• 45 kg ha-1 75 N recovery

8
Balanced nutrition in China
9
Areas of opportunity for improvement in
fertilizer N efficiency

• Continued improvement in cropping system
  management
• Use of site-specific precision ag technologies

10
Site Specific ManagementAccounting for spatial
variability
11
Spatial variability in fertilizer N efficiency
Year 1Uniform 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
Murrell and Murrell, 2002
12
Variable N rate contributed to increased N
efficiency
40 ha field divided into 10 zones
9
8
8
7
13 increase in fertilizer N efficiency
6
5
Frequency of zones
4
4
3
2
2
2
2
1
1
1
0
0
28-39
39-50
50-62
62-73
N use efficiency, kg grain/kg applied N
Murrell and Murrell, 2002
13
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?

14
Is the concept of fertilizer use efficiency the
same for P and K as it is with N?
15
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

16
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 PK) Nutrient input
  needed to sustain the system at optimum
  productivity expressed as a removal to use ratio

17
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.

18
Partial K budgets for the U.S. (average of
1998-2000)
USDA-NRCS, 2000 Due to manure distribution
problems relative to crop demand, this likely
overestimates the agronomic contribution.
19
Ratio of K removal by crops to fertilizer applied
plus recoverable manure
20
Percent of Soils Testing Medium or Lower in K in
2001
North America 43
21
Partial P budgets for the U.S. (average of
1998-2000)
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.
22
Ratio of P removal by crops to fertilizer
applied plus recoverable manure
23
Percent of Soils Testing Medium or Lower in P in
2001
North America 47
24
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 lt optimum ratio should be lt 1
• Soil test levels gt optimum ratio should probably
  be gt 1

• Starter fertilizer needs are often independent of
  soil test levels or removal to use ratios

25
State level P assessment R/(FM)
1.8
1.6
1.4
1.2
1.0
Est. crop removal / (fertilizer manure use)
0.8
0.6
0.4
0.2
0.0
-15
-10
-5
0
5
10
15
20
25
State median soil test level - target level, ppm
Target level lower end of high category
26
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
27
Examples of apparent recovery efficiency of P
fertilizer in long term studies
GH Green house F Field.
Fixen, 1992
28
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

29
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

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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