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

Mississippi
River Basin
Nitrogen
1200000
1000000
800000
600000
400000
200000
0
2.5
2.0
1.5
1.0
0.5
Nitrate-N
0.0
2.5
2.0
Total N
1.5
1.0
Particulate/organic N
0.5
Ammonium
0.0
1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015

Mississippi River Basin Phosphorus
1200000
1000000
800000
600000
400000
200000
0
0.25
Total P
0.20
0.15
0.10
0.05
Soluble reactive P
0.00
1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015

Major Mississippi Subbasins

Major Mississippi Subbasins

Nutrient loads for
2001 to 2010
50
40
30
2001-2005
2006-2010
Total P
20
10
0
350
300
250
200
150
Nitrate-N
100
50
0 on fton
M iss-
Clint
Gra
M iss-
M issou ri-
Om
M issou ah a an n be s ne lto n ri-
Herm
M iss-
The
Oh io-Can
Oh io-G ran d
Cha in tle
Rock
A rkan sas-Lit
Riv
Red er-A lex an dra
Lo w er
M iss
Subbasin

Nutrient yields for
2001 to 2010
3.0
2.5
2.0
1.5
1.0
0.5
2001-2005
2006-2010
Total P
0.0
16
14
12
10
8
6
Nitrate-N
4
2
0
M is s-
C lint on
M is s-
Gr af ton
M is sour
M i-Om aha is sour nn i-H erma
M is s-
Thebe s anne lto n and
C hain
Lit tle
Ohio-C
Ohio-Gr
A rkans as-
R ed
R iv
R ock er-
A lex andra
Low er M is s
Subbasin

Spring nitrate, upper Miss and Ohio
30
25
20
15
10
5
0
30
25
20
15
10
Mississippi River at Grafton
5
Ohio River at Grand Chain, IL
0
1975 1980 1985 1990 1995 2000 2005 2010 2015
0.30
0.25
0.20
0.15
0.10
0.05
0.00
0.30
0.25
0.20
0.15
0.10
Mississippi River at Grafton
0.05
Ohio River at Grand Chain, IL
0.00
1975 1980 1985 1990 1995 2000 2005 2010 2015

Source of spring nitrate
0.7
0.6
0.5
0.4
0.3
0.2
MRB
Grafton and Ohio
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)

inputs
Nutrient Balances
+ +
- 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
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 N ha -1
-5 - 20
20 - 40
40 - 60
60 - 200
Some counties negative, N from soil mineralization

Illinois N budget through
2012
100
80
Fertilizer
60
40
Legume N
20
NOy deposition
0
120
100
80
60
40
20
0
Grain harvest
Human consumption
50 Net Nitrogen Inputs
40
30
Manure
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

Embarras River
20
15
10
5
0
19931994199519961997199819992000200120022003200420052006200720082009201020112012

Embarras River
40
30
20
10
60
50
0
199519961997199819992000200120022003200420052006200720082009201020112012
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 Row Crop %
Manure P Net P Inputs
From Jacobson et al. (2011)

Modeled January to June Total P
From Jacobson et al. (2011)

Illinois P budget through
2012
20
15
10
Fertilizer
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
• limited in-stream losses of nitrate during high flow periods
– Lake
Shelbyville
– Saylorville
Reservoir
• retention times too short
• spring nitrate, headed to Gulf
100
80
60
40
20
0
0.1
Lake Shelbyville, Illinois
Garnier et al. (1999)
Royer et al. (2004)
Saylorville Reservoir, Iowa
Crumpton equation
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
30
25
Corn-Corn-Soy
Miscanthus
Switchgrass
Prairie
20
15
10
5
0
J a n
0
8
J u l0
8
J a n
0
9
J u l0
9
J a n
1
0
J u l1
0
J a n
1
1
J u l1
1
J a n
1
2
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!