Title: Fertilizer Use Efficiency: the North American Experience
1Fertilizer 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
2Fertilizer 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
3Traditional 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
4Agronomic 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
5N fertilizer recovery efficiency using on-farm
measurements Opportunity for improvement
Cassman et al., 2002
6Areas 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
7Balanced 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
8Balanced nutrition in China
9Areas of opportunity for improvement in
fertilizer N efficiency
- Continued improvement in cropping system
management - Use of site-specific precision ag technologies
10Site Specific ManagementAccounting for spatial
variability
11Spatial 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
12Variable 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
13Areas 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?
14Is the concept of fertilizer use efficiency the
same for P and K as it is with N?
15The 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
16We 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
17P 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.
18Partial 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.
19Ratio of K removal by crops to fertilizer applied
plus recoverable manure
20Percent of Soils Testing Medium or Lower in K in
2001
North America 43
21Partial 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
23Percent of Soils Testing Medium or Lower in P in
2001
North America 47
24Viewing 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
25State 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
26Estimating 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
27Examples of apparent recovery efficiency of P
fertilizer in long term studies
GH Green house F Field.
Fixen, 1992
28If 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?
- 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
29Impact 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
30Impact 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