Transcript Slide 1

Effective Nutrient Management
Decisions …
Looking Beyond the Next Harvest
Paul Fixen, Potash & Phosphate Institute
Fernando Garcia, INPOFOS
www.inpofos.org
www.ppi-ppic.org
AAPRESID Congress, 2006
Africa, May 2006…
Parts of Africa burn each year
because of the importance
of crop nutrients
Earth Observatory - NASA
Southern
Congo
Basin
Ballard-Tremeer, 2006
Photo by Mike Braby
Much at stake
At least 30-50% of crop yield is attributable
to commercial fertilizer nutrients
Stewart et al., 2005
Science has never had a
more complete set of
“knowledge nuggets”.
Industry has never had a
more impressive set of
technologies.
Adsorption Index (mg kg-1)
0
150 300 450 600 750 900 1050
0
150 300 450 600 750 900 1050
0.0
Soil Depth (m)
0.2
Wright
0.4
The challenge:
0.6
0.8
1.0
1.2
Delivering science and technology to the farm such that it
can be integrated in support of decision making
No Manure
1.4
1.6
Manure
No N or P
135 N + 0 P
135 N + 80 P
No N or P
135 N + 0 P
135 N + 80 P
1.8
Highly P fixing soil
Site factors in nutrient management decisions
Crop - yield potential, value, tissue levels, leaf color, cultural practices
Soil - soil nutrient supply indexes, other properties
Grower - land tenure, capital supply, opportunity costs, objectives
Nutrient inputs - available commercial forms, wastes, costs
Water quality - set back restrictions, ground water regulations
Climate - probabilities for relevant events (for models)
Weather - for real-time model input
Technology - what’s available and appropriate
Typical nutrient management decision process
Possible site
factors
Crop
Soil
Grower
Nutrient inputs
Water quality
Climate
Weather
Technology
Decision support
Crop demand
Soil supply
Input efficiency
Economics
Environmental
Grower/Owner
Focus today will be on factors
having long-term consequences
Fixen, 2005
Recommended rates
Event probability
Economic return
Environmental impact
Application timing
Etc.
Output
Decision
Action
Outcome
Feedback
loop
Effective Nutrient Management
Decisions …
Looking Beyond the Next Harvest
Efficiency
vs.
effectiveness
Efficiency vs. effectiveness:
a single-season crop response example
Greatest effectiveness
Yield response
Lowest
efficiency
effectiveness
Greatest efficiency
Lowest
Applied P
Effectiveness depends on how well the
goals of nutrient management are met
 Short-term goals




Maximize net returns to fertilizer investments
Eliminate deficiencies
Improve effectiveness of other inputs
Meet short-term production goals
 Long-term goals
 Improve soil productivity
 Increase land value
 Maximize effectiveness of other inputs
 Meet long-term production goals
Short term vs long term goals
 A challenge: avoid confusing true gains in
system level efficiency with practices that simply
borrow from future productivity
 Case studies in Dobermann et al., 2005:
 Soybeans in Hawaii (P)
 Rice in Philippines (P&K)
 Cotton in California (K)
 Maize in Nebraska (N)
N use efficiency in irrigated maize in Nebraska
with recommended or intensive management
Recommended: 7,500 p/ha; soil test-based fertilizer rates; 2 N splits.
Intensive: 10,500 p/ha; higher fertilizer rates; 4 N splits + fall N on residue.
4-year averages
Maize yield, t/ha
Avg. Fertilizer N rate, kg/ha
N removed in grain, kg/ha
Rec.
14.0
195
167
Int.
15.8
305
198
Partial factor prod., kg grain/kg N applied
Removal efficiency, %
72
86
52
65
Measured change in soil organic N, kg/ha/yr
-58
+55
(N removal + change in soil N)/N applied, %
56
83
System level efficiency
Dobermann et al., 2005
Effective Nutrient Management
Decisions …
Looking Beyond the Next Harvest
Soil organic matter
Crop removal and P budgets
Organic C levels in soils of the northern
Pampas since beginning of agriculture
(Argiudolls)
Carbon (t/ha)
80
60
40
43% of
original
20
y = -6,4 Ln(x) + 70
2
R = 0,71
0
0
30
60
90
120
Years under cropping
Source: Alvarez y Steinbach (2006) from data of Andriulo and Cordone (1998)
Nutrient Depletion in the Pampean Region
Typic Argiudoll - Arroyo Dulce Series
Original = Undisturbed for at least the last 18 years
Cropped = 30 years of annual cropping (20 years soybeans)
Property
Organic matter (%)
pH
Total Nitrogen (g/kg)
Bray P (mg/kg)
Exch. Ca (cmol/kg)
Exch. Mg (cmol/kg)
Exch. K (cmol/kg)
Zinc (mg/kg)
Copper (mg/kg)
Boron (mg/kg)
Original
5.3
6.2
2.8
123.5
10.1
2.4
2.3
3.9
3.5
0.77
Cropped
3.5
6.0
1.9
14.9
10.0
1.9
1.3
1.9
2.4
0.28
66% of
original
Urricarriet y Lavado, 1997
Simulated total soil C changes for the central
U.S. Corn Belt (Lal et al., 1998)
61% of
1907
(0-20-cm depth)
Litter fall & root production has been
less than decay … So what?
Janzen, 2006
Hypothetical hydroelectric plant
Crop
residues
Soil
organic
matter
Biological
benefits
O.M.
decay
 Opening valve B temporarily increases power generation, but at the
expense of water storage.
 Closing valve B increases water stored, but reduces power
generation.
 Increasing both storage and power requires an increase in water
inflow.
Janzen, 2006
Organic C evolution during 40 years
Rotations Study INIA La Estanzuela (Uruguay)
3.0
COrganic
orgánico
C (%)
2.5
2.0
1.5
S1
S2
S5
S7
1.0
0.5
0.0
1958
1968
1978
1988
1998
2008
Years
Años
S1: Continuous row cropping without fertilization
S2: Continuous row cropping with fertilization
S5: 50% row cropping 50% pastures
S7: 66% row cropping 33% pastures
Source:
A. Morón (2003)
Influence of 45 years of N and P fertilization of
irrigated maize on soil organic matter content
Soil organic matter, %
2.8
0-15 cm
Bray P-1
ppm
2.6
26
2.4
5
2.2
Tribune, KS
2
0
50
100
150
Fertilizer N, kg/ha
Schlegel, 2006
200
250
Soil carbon in 0-7.5 cm soil depth as a
function of N and P fertilizer rates.
77 kg P2O5/ha
No P fertilizer
0
Halvorson and Reule, 1999
22
45 67 90 112 135 157 179
N fertilizer rate, kg/ha
Insufficient P leads to reduced C
sequestration … bad for soils, bad for climate
Root carbon costs of bean genotypes
 Low P plants:
 Lose more C through
root respiration
 Have increased root
exudation of C
 Often have increased
physiological C costs
P-inefficient
genotypes
Lynch and Ho, 2005
P-efficient
genotypes
Crop nutrient removal
 Provides a basic reference point for evaluating
impact of current practices on soil fertility
 Most effective when combined with soil test
information
Negative budgets reduce soil test P
Bray P-1 (ppm)
50
45
40
35
147 Kg P in 1975
30
25
20
15
10
0 P in 1975
19
75
19
76
19
77
19
78
19
79
19
80
19
81
19
82
19
83
19
84
19
85
19
86
19
87
19
88
19
89
5
0
Data source: Webb et al., 1992 (Iowa)
Average P use on corn and soybeans in
the U.S. relative to crop removal
60.0
Fert. + Manure P
P2O5 , kg/ha
50.0
40.0
Use
30.0
Removal
20.0
10.0
1960 1965 1970 1975 1980 1985 1990 1995 2000
Fixen and Murrell, 2002
Percent of samples testing medium or below
in P in the Corn Belt.
55
R2 = 0.72
Medium or below , %
50
45
40
35
Removal < Use
30
1970
1975
Fixen and Murrell, 2002
1980
Removal > Use
1985
1990
1995
2000
2005
U.S. Corn Belt states: P application/removal
ratios for field crops
Fert use/rem.
0.90
0.80
0.70
1.00
IL
IN
IA
MN
(Fert. + manure use)/rem.
1.00
0.60
0.50
0.40
0.30
0.20
2000
2001
After Murrell, 2006.
2002
2003
2004
2005
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
2000
Median soil P, ppm
IL 36
IN 29
IA 25
MN 18
IL
IN
IA
MN
2001
2002
2003
2004
2005
A closer look at the state of Illinois
BC
AB
MB
SK
ON
PQ
PEI
WA
NB
ME
MT
ND
NS
MN
OR
VT
ID
NY
WI
SD
MI
WY
IA
PA
NE
NV
IL
IN
MD
UT
VA
MO
KS
KY
NC
AZ
DE
WV
CO
CA
NJ
OH
TN
OK
NM
AR
SC
MS
TX
AL
GA
LA
FL
P budget for the state of Illinois by watershed
State total, million lbs P2O5
+ Applied fertilizer (2005)
613
+ Recoverable manure (1997) 77
- Crop removal (2005)
1,075
Net budget
-385
Use to removal ratio
0.64
Median Bray P-1 level for 2005 crop = 36 ppm
Removal and application of nutrients in
wheat, corn, soybean, and sunflower
2004/2005 Season
NPKS removal
Girasol
Soja
Trigo
Maíz
902
1500
1200
900
600
391
300
240
0
1800
thousand ton
thousand ton
1800
1836
NPKS appication
1500
1200
900
600
522
165
300
0
N
P
K
S
N
P
17
33
K
S
In the 2004/05 season, application of N, P, K, and S accounted for 28%, 42%, 2% y
13% of the N, P, K, and S removed, in corn, wheat, soybean, and sunflower
Argentina: Application/Removal Ratios for N,
P, K and S in field crops
Application/Removal ratio
0.5
P
0.4
0.3
N
0.2
S
0.1
K
0
1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004
Year
The ratios are increasing by 1.2%, 2.1%, 0.1%, and 1.1% per year
for N, P, K, and S, respectively
P balance for
grain crops
Estimated for 2002/03
kg/ha
Elaborated from data of Fundación
Producir Conservando
Maps developed with ArcView ®
Available P in soils of the Western pampas
35
Bray P (ppm)
30
25
20
y = -0.40x + 814.30
R = 0.42
2
15
n=1847
10
5
0
1970
1975
1980
1985
1990
1995
2000
2005
2010
Source: Díaz-Zorita, Duarte & Asoc. (2005)
Fertilizing the system: Replenishing N, P,
and S … economic results
Averages of 5 trials of the Nutrition Network CREA Southern
Santa Fe Rotation C-W/S – 6 years (3 cycles of the rotation)
U$/ha
1800
1507
1200
1090
600
417
0
Fertilizer cost
Gross income
Gross margin
 Treatments compared were check and NPS (100% replenishment)
 Grain prices (U$/t) Corn: 80 – Wheat: 90 – Soybean: 165
 Nutrient prices (U$/t) Urea: 380 – MAP: 380 – Calcium sulfate: 150
 Average annual rates 126 kg N + 36 kg P + 21 kg S
Source: CREA Sur de Santa Fe-INPOFOS-ASP
Residual effects of fertilization
Grain yield (kg/ha)
Experiment El Fortín – Gral. Arenales (Buenos Aires)
Nutrition Network CREA Southern Santa Fe 2004/05 and 2005/06
9000
8000
7000
6000
5000
4000
3000
2000
1000
0
8288
Check between 2000 and 2003
NPS between 2000 and 2003
7257
5180
2976
Wheat 2004
2715
3274
Soybean 2004/05
Corn 2005/06
Wheat/soybean 2004/05: All fertilized with 86 kg N + 27 kg P + 10 kg S
Corn 2005/06: All fertilized with 88 kg N + 26 kg P + 10 kg S
Source: CREA Sur de Santa Fe-INPOFOS-ASP
5.4
35-48
Yield, t/ha
4.9
“On impoverished soils (<10 ppm P)
even the largest fresh applications
of broadcast P did not raise yields
to those achieved on enriched soils
(>25 ppm P) in the absence of fresh
phosphate.”
23
4.3
6
3.8
A.E. Johnston, 1986
Olsen P
6 ppm 23 ppm
3.2
35 ppm
2.7
48 ppm
*
0
56
112
168
Applied P2O5, kg/ha
224
Yields were higher where soil P was increased
with an initial broadcast application compared
to annual banding at a lower soil P level
Relative yield,
percent of maximum
110
Olsen soil test
at end of 5-yr:
15 ppm
100
90
Amount broadcast
initially, kg P ha-1
80
0
5 ppm
80
70
5-yr averages
60
0
5
10
15
20
Annual rate of seed placed P (kg P ha-1)
Wager et al., 1986
Effects of soybean expansion on the soil
system
Soybeans dominate the rotation
(soybean monoculture)
Low C input
to the system
Corn, wheat or other
crops are not
profitable
SOM
decreases
Field at Southeastern
Cordoba under continuous
soybean
Biological, chemical and physical
soil properties are affected
Soil profile showing
compacted zones (red marks)
at 10-15 cm
Leased land in Argentina
 Estimated that 50% of cropped land in Pampas
is leased
 Recent survey of 131 farmers in southern Santa
Fe province (central Pampas) on % of cropped
land leased
 Farms < 200 ha: 28% leased
 Farms > 200 ha: 60% leased
(Source: Cloquell et al., 2005)
Percent of land in farms rented
or leased in 2002 in the U.S.
U.S. 28.4%
Impact of duration of land use and capital
supply on target Bray P-1 soil test levels
Target soil test levels for the following
durations of land use (yr.)
Capital
1
4
More than 8
-------------- (mg P kg-1) -------------Very limited
4
14
20
Limited
6
16
21
Available
9
18
22
Based on PKMAN modeling approach with a visual interpretation of
Iowa State Univ. calibration data for maize and soybean
Summary
 Effective nutrient management should consider numerous site-specific




factors, some of which have long-term consequences
Sustainable management involves finding a balance between crop
residue addition and the benefits of organic matter decay
 Appropriate nutrient management can supply more crop residue to
the soil and increase system C retention
P removal exceeds use in the Pampas and the U.S. Corn Belt
 Soil testing can help predict when deficit budgets will reduce
productivity and profitability
Rented land is common in the Pampas and the U.S. Corn Belt and can
serve as a deterrent to increasing soil productivity
 There is a need for leases that equitably share the short-term costs
of practices that return long-term benefits
The Argentine Pampas and the U.S. Corn Belt have similarities in
characteristics and challenges to long-term sustainability
 Continued cooperative sharing of research results should help meet
those challenges and help us all look … beyond the next harvest
Effective Nutrient Management
Decisions …
Looking Beyond the Next Harvest