Transcript Overview of Nitrogen Mass Balances in Agricultural Ecosystems

Overview – Nutrient
Fate and Transport
Mark B. David
University of Illinois at Urbana-Champaign
Presented at Building Science Assessments
for State-Level Nutrient Reduction
Strategies
Nov. 13, 2012
What I will cover
• what the problem is
• N and P sources, balances, and river exports in the
Mississippi River Basin (MRB)
– Illinois as example
– what is going to the Gulf
• importance of modified hydrology (tile drainage)
• timing of flow and nutrients; fate
• myths; the challenge ahead
What is the problem?
• both local and
downstream water quality
problems from nitrate
and total P
– local: algal production due
to P; drinking water for N
– downstream: hypoxia in
the Gulf of Mexico
• USEPA requiring nutrient
criteria in flowing waters
Hypoxic zone, 2012
What was new (in 2007, now old)
• reaffirmed previous assessment
• importance of spring (April, May, June)
nitrate
• now phosphorus recognized as having role in
Gulf
• no one answer to fix problem
– both agriculture and people (sewage effluent)
• recommended 45% reduction in N and P
going down Mississippi River
3
Water Flux (million m )
1200000
1000000
800000
600000
400000
200000
0
2.5
Nitrate-N
1.5
1.0
0.5
0.0
2.5
Total N
2.0
1.5
1.0
Particulate/organic N
0.5
Ammonium
15
20
10
20
05
20
00
20
95
19
90
19
85
19
80
19
75
19
70
19
65
19
60
19
55
0.0
19
Riverine N Flux
-1
(million metric tons N yr )
Mississippi
River Basin
Nitrogen
2.0
3
Water Flux (million m )
Riverine P Flux
-1
(million metric tons yr )
Mississippi River Basin Phosphorus
1200000
1000000
800000
600000
400000
200000
0
0.25
Total P
0.20
0.15
0.10
Soluble reactive P
0.05
15
20
10
20
05
20
00
20
95
19
90
19
85
19
80
19
75
19
70
19
65
19
60
19
19
55
0.00
Major Mississippi Subbasins
Major Mississippi Subbasins
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Nutrient
loads for
2001 to 2010
Nutrient load (1,000 metric tons N or P yr )
50
2001-2005
2006-2010
Total P
30
20
10
0
350
300
Nitrate-N
250
200
150
100
50
0
Subbasin
M
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Nutrient
yields for
2001 to 2010
-1
-1
Nutrient yield (kg N or P ha yr )
3.0
2.5
2001-2005
2006-2010
Total P
2.0
1.5
1.0
0.5
0.0
16
14
Nitrate-N
12
10
8
6
4
2
0
Subbasin
Spring nitrate, upper Miss and Ohio
0.30
30
25
Mississippi River at Grafton
0.25
0.20
Riverine Nitrate-N Flux
(million metric tons N)
20
Water Flux (cm)
15
10
5
0
30
25
20
15
0.10
0.05
Mississippi River at Grafton
0.00
0.30
0.25
0.20
0.15
0.10
10
5
0.15
0.05
Ohio River at Grand Chain, IL
0
1975 1980 1985 1990 1995 2000 2005 2010 2015
Ohio River at Grand Chain, IL
0.00
1975 1980 1985 1990 1995 2000 2005 2010 2015
Spring Nitrate (tons N yr-1)
Source of spring nitrate
0.7
0.6
MRB
Grafton and Ohio
0.5
0.4
0.3
0.2
0.1
0.0
1975 1980 1985 1990 1995 2000 2005 2010 2015
County Level Analysis of
Mississippi River Basin
• counties in MRB (all 1768)
• 1997 to 2006 annual data on fertilizer,
crops, animals, people, deposition
• predictive model from watersheds applied
to all MRB counties
• both N and P
From David et al. (2010)
Nutrient Balances
inputs
+
+
- outputs
-
-
Annual N Fertilizer Applications
Fertilizer (kg N ha-1)
0.0 - 11.2
11.3 - 27.2
27.3 - 45.4
45.5 - 65.9
66.0 - 107.1
From David et al. (2010)
Tile drainage is concentrated in the
corn belt
Drain of county
Fraction
0.0 - 5.1
5.2 - 16.3
16.4 - 31.7
31.8 - 51.4
51.5 - 81.8
From David et al. (2010)
Net N Inputs (NNI)
kg
nni N ha-1
-5 - 20
20 - 40
40 - 60
60 - 200
Some counties negative, N from soil mineralization
100
80
Fertilizer
60
Legume N
20
-1
Nitrogen (kg N ha )
Illinois N
budget
through
2012
40
NOy deposition
0
120
100
Grain harvest
80
60
40
20
Manure
Human consumption
0
50
Net Nitrogen Inputs
40
30
20
10
0
1950
1960
1970
1980
1990
2000
2010
Linking N balances to N Export
• hydrology overwhelming factor
– channelization, tile drainage
• can look at watershed N export as a fraction
of net N inputs
– most studies, about 25%
– however in MRB we know it is larger in critical
areas
– can be > 100% in heavily tile drained watersheds
Drainage by tiles and ditches
Patterned tile
systems
Embarras River - Camargo
9
19 3
9
19 4
95
19
9
19 6
9
19 7
98
19
9
20 9
0
20 0
01
20
02
20
0
20 3
0
20 4
05
20
0
20 6
0
20 7
08
20
0
20 9
1
20 0
1
20 1
12
19
NITRATE (mg N L )
-1
Embarras River
20
15
10
5
0
Embarras River
-1
-1
Nitrate Export (kg N ha yr )
60
50
40
30
20
10
0
95 996 997 998 999 000 001 002 003 004 005 006 007 008 009 010 011 012
9
1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 2 2 2
Water Year
Modeled January to June Nitrate Export
Predicted N Yield (kg N/ha)
0.00 - 3.00
3.01 - 7.50
7.51 - 10.00
10.01 - 15.00
15.01 - 25.00
Best model includes fertilizer, sewage effluent,
and tile drainage
Components of P Mass Balances
• net P inputs
= inputs – outputs
inputs (fertilizer)
outputs (grain harvest - human and animal
consumption)
• net indicates additions or removals from soil
• little P (relative to N) is lost to streams, but
it is biologically important
• surface runoff and tile leaching
• manure
Fertilizer P
Manure P
Row Crop %
Net P Inputs
From Jacobson et al. (2011)
Modeled January to June Total P
From Jacobson et al. (2011)
20
15
Fertilizer
10
-1
Phosphorus (kg P ha )
Illinois P
budget
through
2012
5
0
20
15
Grain harvest
10
5
Manure
Human consumption
0
20
15
10
5
Balance
0
-5
-10
1950
1960
1970
1980
1990
2000
2010
P from
fields to
rivers –
Embarras
River
From Gentry et al. (2007)
Particulate
P from
fields to
rivers
From Gentry et al. (2007)
Importance of a Few Storm Events
From Royer et al. (2006)
Fate of N
– Lake
Shelbyville
– Saylorville
Reservoir
• retention times
too short
• spring nitrate,
headed to Gulf
100
N Removed (%)
• limited in-stream
losses of nitrate
during high flow
periods
Lake Shelbyville, Illinois
Garnier et al. (1999)
Royer et al. (2004)
Saylorville Reservoir, Iowa
80
Crumpton equation
60
40
20
0
0.1
1
10
100
1000
Depth/Time of Travel (m yr-1)
10000
Fate of P
• some sediment removal
• problem of sediment
already in streams/rivers
– stream bank, bed erosion
• algal biomass can move
downstream
• no way to easily get out
of system (like nitrate)
Source: Clay Soil and Water Conservation
District, Minnesota
What we know about nutrient sources
• Upper Mississippi and Ohio
subbasins are the major
source of nitrate and total P
– even more so in critical spring
period
• the tile drained cornbelt is
clearly identified
• mass balance of P has greatly
decreased, but not N
What can we do in agriculture?
• given,
– it is not typically over fertilization
based on current rates and yields
– may be zero or negative N & P balances
in some areas of the tile drained
Midwest
• three types of conservation
practices could help
– nutrient-use efficiency
– in-field management
– off-site measures
Potential Efficiencies -SAB report
Perennial biofuels quickly reduce
nitrate loss
Corn-Corn-Soy
Miscanthus
Switchgrass
Prairie
25
20
15
10
5
Ja
n1
2
Ju
l11
Ja
n1
1
Ju
l10
Ja
n1
0
Ju
l09
Ja
n0
9
Ju
l08
0
Ja
n0
8
Nitrate-N Concentration
(mg N L-1)
30
From Smith et al. (2013)
Point sources in MRB?
• sewage effluent and
industrial (22% of annual
N and 34% of P)
• however, only 14% (N) and
20% (P) of spring load
• not going to solve problem,
but could help for P
A few myths
• no-till solves all problems
• a few (bad) actors are the problem
• over application of N (or P) is most of the
problem
• just targeting a few fields will solve most of
the problem
• edge of field denitrification can solve the
problem
• the response will take a long time (decades?)
What’s making it difficult
• more corn (and fertilizer)
• more intensive tile drainage
• warmer winters
• more intense winter/spring precipitation
• fall N in Illinois, Indiana, Ohio
• the intensity of agriculture across the
cornbelt
• many (most?) practices to reduce nutrient
loss don’t increase yield
Conclusions
• N and P balances don’t relate well to nitrate and P loss
across the MRB (but could increase losses in a drought
year)
• counties with high fertilizer inputs have high crop
fractions (& corn acres) and tile drainage
– all lead to nitrate loss
– corn & soybeans on tile drained land much more important
than manure, deposition, or sewage effluent
• P from both surface runoff and tiles
– sewage effluent also important
• high winter/spring flow and nutrient losses are a
challenge, and seem to be getting worse
Job ahead for us
• 45% reductions in N and P will be quite difficult
in upper MRB
• we haven’t really started
– not in any meaningful way
• variety of methods and costs
– many or most unrelated to yields
• scale of problem is impressive
• but, we do know how to do it!