An economic analysis of soil erosion control in a watershed representing Corn Belt conditions


Nelson, M.; Seitz, W.

North Central Journal of Agricultural Economics 1(2): 173-186

1979


The economic impacts of soil erosion control and nitrogen use controls at the farm and watershed levels of aggregation are presented. A multiple-farm-level linear programming model of the production of crops in five-year rotations is used. The model, constructed to represent a 100-year period, gives estimates of the impacts of soil loss and nitrogen use controls at the farm and watershed levels of aggregation over time. Estimates of the impacts on crop selections, soil losses, conservation, and tillage practices and net incomes at the farm and watershed levels are presented.

AN
ECONOMIC
ANALYSIS
OF
SOIL
EROSION
CONTROL
IN
A
WATERSHED
REPRESENTING
CORN
BELT
CONDITIONS
ABSTRACT
The
economic
impacts
of
soil
erosion
con-
trol
and
nitrogen
use
controls
at
the
farm
and
watershed
levels
of
aggregation
are
presented.
A
multiple
-farm
-level
linear
programming
model
of
the
production
of
crops
in
five-year
rotations
is
used.
The
model,
constructed
to
represent
a
100
-year
period,
gives
estimates
of
the
impacts
of
soil
loss
and
nitrogen
use
controls
at
the
farm
and
watershed
levels
of
aggregation
over
time.
Estimates
of
the
impacts
on
crop
se-
lections,
soil
losses,
conservation,
and
tillage
practices
and
net
incomes
at
the
farm
and
watershed
levels
are
presented.
A
basic
problem
the
world
will
face
in
future
years
is
the
strain
of
an increasing
population
on
limited
land
resources.
According
to
moderate
growth
as-
sumptions
the
world
population
is
estimated
to
ex-
ceed
six
billion
by
the
year
2000.
It
has
been
esti-
mated
that,
by
the
year
2000,
food
output
must
triple
1965
output
if
widespread
starvation
is
to
be
avoided.
Food
output
must
expand
considerably
more
than
three
times
to
provide
an
adequate
diet
[1,
p.
120]
.
If
adequate
food
supplies
are
to
be
forthcoming,
land
will
have
to
be
a
primary
factor
in
meeting
the
initial
major
impact
of
increased
food
and
fiber
demand.
This
projected
increase
in
demand
will
encourage
more
intensive
use
of
land
susceptible
to
serious
soil
erosion.
As
an
indication
of
the
magnitude
of
the
po-
tential
erosion
problem,
Davis
[2,
p.
68]
,
reports
that
farmers'
attempts
to
increase
output
during
the
1973-74
cropping
seasons
resulted
in
approxi-
mately
60
million
additional
tons
of
soil
loss
from
about
four
million
acres
of
land
with
inadequate
soil
erosion
protection.
It
seems
imperative
that
further
decline
in
productivity
of
soils
as
a
result
of
erosion
must
be
prevented
if
projected
demands
for food
and
fiber
are
to
be
met.
Mack
C.
Nelson
is
assistant
professor
of
agricultural
economics,
The
Fort
Valley
State
College,
Fort
Valley,
Georgia.
Wesley
D.
Seitz
is
professor
of
agricultural
economics
and
associate
director
of
the
Institute
for
Environmental
Studies,
University
of
Illinois
at
Urbana
-Champaign.
This
research
is
conducted
with
the
support
of
the
U.
S.
Environmental
Protection
Agency
contract
#68-01-3584
and
the
cooperation
of
the
Agricultural
Experiment
Sta-
tion,
University
of
Illinois
at
Urbana
-Champaign.
The
con-
tributions
of
other
members
of
the
research
team
and
the
suggestions
of
the
editors
are
appreciated.
Mack
C.
Nelson
and
Wesley
D.
Seitz
While
scientists
do
not
agree
that
individual
crop
producers
should
significantly
reduce
soil
loss
to
maintain
soil
productivity,
most
do
agree
that
high
rates
of
soil
loss
reduce
productivity
and
in-
flict
offsite
damages
that
are
in
some
instances
more
costly
than
reduced
productivity
[10,
p.
58]
.
1
This
article
presents
estimates
of
the
economic
impacts
of
selected
environmental
policies
on
crop
producers
in
the
Big
Blue
Creek
watershed
located
in
northeastern
Pike
County,
Illinois.
This
approxi-
mately
27,000
acre
area
was
chosen
because
it
had
been
judged
representative
of
the
Corn
Belt
in
re-
gard
to
its
soils,
its
soil
erosion
problem,
and
its
production
of
important
agricultural
products
[9,
p.
18]
.
2
Time
and
resource
constraints
made
it
necessary
to
select
a
sample
of
farms.
The
percent-
ages
of
land
in
each
of
the
major
soil
types
of
the
total
nine
-farm
sample
is
nearly
the
same
as
those
of
the
watershed.
The
farmers
were
selected
to
represent
typical
actual
farms
in
terms
of
the
amount
of
various
types
of
soils
in
the
farm,
but
precise
farm
boundary
lines
were
not
used
in
de-
scribing
the
farms.
Thus
several
farms
are
quite
flat
and
highly
productive
while
others
are
hilly
and
less
productive.
The
percent
of
the
land
by
slope
class
and
an
estimated
productivity
index
(bushels
of
corn
per
acre)
are
given
in
table
1.
The
sample
farms
permit
generalization
of
im-
pacts
to
the
watershed
and
to
the
Corn
Belt
and
to
surrounding
areas
to
a
much
lesser
extent.
The
im-
pacts
of
the
following
policies
are
estimated:
(a)
unrestricted
soil
loss
and
fertilizer
use;
(b)
restric-
tion
of
soil
loss
per
individual
farm
to
those
levels
recommended
by
the
Soil
Conservation
Service
(SCS);
(c)
restriction
of
fertilizer
use
to
50
and
100
pounds
per
acre;
and
(d)
restriction
of
individual
farms
to
a
combination
of
soil
loss
levels
recom-
mended
by
the
SCS
and
nitrogen
use
limits
of
50
and
100
pounds
per
acre.
1
Some
scientists
seem
to
suggest
that
what
is
reduced
is
only
the
native
productivity
of
the
soil,
which
may
be
supplemented
by
chemical
fertilizer
to
economically
main-
tain
the
initial
production
level.
2
Taylor
and
Frohberg
report
that
production
in
this
area
(the
Corn
Belt)
accounts
for
approximately
70
percent
and
60
percent
respectively,
of
the
total
United
States
corn
and
soybean
production.
It
is
also
important
to
note
that
corn
and
soybeans
are
the
most
erosive
crops
commonly
grown
in
the
Corn
Belt.
174
NORTH
CENTRAL
JOURNAL
OF
AGRICULTURAL
ECONOMICS,
Vol.
1,
No.
2,
July
1979
TABLE
1.
Productivity
index
and
distribution
of
land
by
slope
group
for
nine
sample
farms,
Big
Blue
Creek
Watershed,
Illinois
FARM
NUMBER
Productivity
index
A=0-2%
Percent
of
land
in
each
slope
group
F=18-30%
G>30%
TOTAL
ACRES
B=2-4%
C=4-7%
D=7-12%
E=12-18%
(bushels
of
corn
per
acre)
1
125
5.7
51.0
26.3
17.0
187.5
2
150
41.4
37.3
16.5
4.7
185.9
3
120
18.4
18.8
26.0
23.6
13.2
156.2
4
110
42.4
9.5
1.9
0.8
45.4
296.2
5
120
10.0
27.6
31.2
14.8
9.4
7.0
206.3
6
105
21.4
11.1
19.5
19.6
21.3
2.5
4.6
432.2
7
100
23.6
21.1
15.7
11.9
24.7
3.0
267.5
8
105
14.2
23.1
28.7
10.5
23.5
286.9
9
100
35.9
35.8
28.3
116.8
Wade
and
Heady
[12,
p.
13]
indicate
that
sedi-
ment
in
streams
is
the
most
abundant
of
all
pol-
lutants
of
U.
S.
waters.
They
point
out
that
sedi-
ment
impacts
are
widespread
and
that
sediment
control
is
interwoven
with
land
use
and
land
use
policy.
As
a
result,
it
appears
that
erosion
-
sedimentation
control
policies
are
a
distinct
possi-
bility.
Taylor
and
Frohberg
[11,
p.
25]
suggest
that
nitrogen
use
limits
within
the
range
suggested
in
this
study,
while
extreme,
are
plausible
under
a
strict
interpretation
of
the
1985
water
quality
goals
set
down
in
the
amended
1972
Federal
Water
Pollution
Control
Act.
Taylor
and
Frohberg,
how-
ever,
do
point
out
that
Illinois,
the
only
Corn
Belt
state
to
give
serious
consideration
to
limiting
ferti-
lizer
use,
determined
that
nitrates
were
not
pre-
sently
a
major
problem
and
recommended
that
controls
not
be
instituted.
Nevertheless,
since
some
water
supplies
in
the
state
have
exceeded
the
U.
S.
Public
Health
Service
standard
for
nitrates,
it
appears
the
issue
remains
to
be
resolved.
THE
MODEL
The
model
used
for
this
analysis
is
a
multiple
-
farm
-level
linear
programming
model
of
the
pro-
duction
of
seven
crops
(corn,
soybeans,
wheat,
oats,
alfalfa,
pasture, and
woodland)
in
five-year
rotations
[5,
p.
87].
3
The
prices
used
in
this
study
3
Where
C
=
corn,
Sb
=
soybeans,
OX
=
oats
(with
an
alfalfa
catch
crop),
W
=
wheat,
and
M
=
meadow
or
alfalfa,
the
rotations
included
in
the
model
were
(1)
C,
(2)
C-Sb,
(3)
C-C-Sb-OX,
(4)
C-C-Sb-W-M,
(5)
W-Sb
(double
crop),
(6)
C
-W
-M
-M,
(7)
Pasture,
and
(8)
Woodland.
were
generated
by
a
market
equilibrium
regional
model
developed
by
Taylor
and
Frohberg
[11,
p.
26]
.
The
market
equilibrium
prices
were
used
so
the
impacts
suggested
for
the
region
could
be
evaluated
at
the
watershed
and
individual
farm
level.
Purchasing
activity
in
the
model
is
limited
to
the
purchase
of
nitrogen.
The
nitrogen
purchasing
activity
ha's
been
included
for
several
reasons.
First,
there
is
evidence
that
nitrogen
(nitrate)
applied
to
agricultural
lands
may
have
detrimental
effects
on
water
quality
if
it
is
present
in
excessive
levels,
and,
second,
the
bulk
of
commercial
nitrogen
produc-
tion
uses
energy
sources
that
are
becoming
increas-
ingly
expensive.
By
modeling
nitrogen
use
as
we
have,
we
are
able
to
make
changes
in
the
price
of
nitrogen
or
limit
the
total
quantity
applied
to
an
area
in
an
efficient
manner.
The
objective
function
maximized
is
annualized
income
above
total
costs
for
a
ten-year
period.
The
eight
rotations
included
in
the
model
can
be
produced
on
all
but
two
soil
types:
Permanent
pasture
and
woodland
activities
are
not
alternatives
on
land
with
slopes
of
4
percent
and
less,
and,
on
soil
types
with
slope
gradients
exceeding
18
per-
cent,
permanent
pasture
and
•woodland
activities
are
the
only
alternatives
available.
The
reasons
for
these
modifications
are
that
slope
group
E
(12-18
percent
slope)
and
above
are
not
generally
used
for
continuous
cropping
activities,
and,
while
soil
slopes
of
4
percent
and
less
can
be
devoted
to
pasture
and/or
woodland
activities,
other
cropping
activities
are
usually
much
more
profitable.
Resource
restrictions
included
in
the
model
are
land,
nitrogen
use,
and
soil
loss.
Land
is
classified
ANALYSIS
OF
SOIL
EROSION
CONTROL,
Nelson
and
Seitz
175
by
soil
type
-slope
-erosion
class.
Each
acre
of
land
within
a
soil
type
-slope
-erosion
class
is
considered
to
be
homogeneous
initially.
Nitrogen
constraints
allow
only
application
rates
of
50,
100,
or
150
pounds
per
acre
on
all
rotations
except
for
pasture
and
woodland.
These
uses
are
allowed
maximums
of
50
pounds
per
acre.
The
nitrogen
application
rates
are
adjusted
to
show
crop
rotation
makeup
and
the
influence
of
previous
crops
on
the
fertilizer
requirements
of
current
crops.
Soil
loss
constraints
are
based
on
maximum
SCS
tolerance
limit
recom-
mendations
[7,
p.
39-40].
Production
cost
data
on
rotation
components
have
been
developed
primarily
from
the
Illinois
Farm
Management
Manual
[3,
p.
4-5]
.
Total
pro-
duction
cost
is
separated
into
direct
costs,
labor
costs,
and
fertilizer
costs.
4
Individual
components
for
estimating
costs
of
producing
the
various
crops
are
related
to
yields.
Pasture
and
woodland
cost
functions
are
viewed
as
long-term
investments
rather
than
annual
costs.
However,
they
are
annual-
ized
for
comparison
with
other
costs.
Conventional,
plow
-plant,
chisel
plowing,
and,
in
the
case
of
the
double
crop
rotation,
zero
tillage
methods
are
used.
5
Conservation
alternatives
are
up
and
down
tilling,
contouring,
and
terracing.
6
All
practices,
however,
are
not
usable
on
all
land
types.
The
choice
of
conservation
practice
is
based
on
Soil
Conservation
Service
recommendations
for
various
slope
gradients
and
soil
loss
coefficients
used
in
the
model
were
based
on
the
universal
soil
loss
equation
[13,
p.
58]
.
MODEL
RESULTS
The
base
model
results,
constrained
only
by
the
individual
land
type
restrictions,
are
presented
in
table
2.
These
results
indicate
that
a
major
por-
tion
(about
80
percent)
of
the
acreage
is
devoted
to
row
crops.
7
Conventional
and
zero
tillage
prac-
4
Direct
cost
includes
preharvesting
soil
preparation,
seeding,
harvesting,
conditioning
power,
and
machinery
depreciation,
repairs,
fuel,
seed,
sprays,
and
other
materials.
The
direct
crop
costs
used
in
this
analysis
was
based
on
260-
to
339
-acre
farm
cost
data.
5
"Conventional
tillage"
consists
of
the
following
oper-
ations:
shredding
or
disking
residue,
plowing
(fall
or
spring),
and
disking
twice
with
harrowing.
"Plow
-plant
til-
lage"
consists
of
shredding
or
disking
residues,
spring
plow-
ing
with
attached
mulcher
or
clodbuster,
and
planting.
"Chisel
-plow
tillage"
consists
of
chiseling
the
residue,
har-
rowing,
and
planting.
"Zero
tillage"
consists
of
preparation
of
a
seed
zone
no
wider
than
two
inches
in
previously
un-
tilled
ground.
Tillage
is
usually
done
by
a
nonpowered,
fluted
coulter
running
ahead
of
a
planter
unit
with
disk
openers.
6
For
a
detailed
discussion
of
the
conservation
prac-
tices,
see
Nelson
[5,
p.
89].
7
The
percent
of
the
watershed
acreage
devoted
to
row
crops
is
calculated
by
dividing
the
row
crop
acreage
(1,705)
by
the
watershed
acreage
(2,136),
see
table
1.
tices
are
used,
and
up
and
down
tillage
is
the
pre-
dominant
conservation
practice.
A
total
of
about
34,000
tons
or
16
tons
of
soil
per
acre
erodes
from
the
model
area,
while
-
an
average
income
of
about
$93
(discounted
at
5
percent)
per
acre
is
gener-
ated.
8
However,
when
soil
loss
constraints
con-
sistent
with
Soil
Conservation
Service
recommen-
dations
are
imposed
on
individual
farms
(table
3),
the
acreage
devoted
to
row
crops
decreases
by
approximately
28
percent
(a
comparison
of
tables
2
and
3).
While
row
crop
acreage
decreases
considerably,
corn
acreage
increases
by
about
49
percent,
and
soybean
acreage
decreases
by
approximately
81
percent
when
compared
with
the
base
model.
Shifts
of
acreage
within
the
row
crops
result
from
attempts
to
maintain
high
levels
of
income
while
reducing
soil
losses.
The
farm
soil
loss
limits
result
in
minor
tillage
practice
adjustments,
but
cause
elimination
of
the
conservation
practice
of
up
and
down
tillage.
Terracing
and
contouring
are
used
in-
stead.
Soil
loss
is
reduced
by
approximately
75
per-
cent,
and
the
watershed
net
income
is
reduced
by
about
9
percent.
The
results
of
restricting
soil
loss
by
imple-
menting
SCS
recommendations
in
combination
with
nitrogen
use
restrictions
to
50
and
100
pounds
per
acre
are
presented
in
tables
4
and
5.
Incomes
are
reduced
by
13
and
10
percent
re-
spectively
compared
with
the
base
model
(table
2),
and
significant
reductions
in
nitrogen
use
are
indi-
cated.
The
one
-hundred
-pound
nitrogen
use
restric-
tion
in
combination
with
SCS
soil
loss
tolerance
recommendations
results
in
row
crop
acreage
de-
creases
of
34
percent
compared
with
the
base
model
(table
2).
Under
this
restriction
a
larger
per-
centage
of
row
crop
acreage
is
devoted
to
corn
than
is
the
case
with
the
base
model.
9
This
result
is
a
general
indication
that
the
soil
loss
restriction
impact
is
more
severe
than
the
impact
of
nitrogen
use
on
crop
selection
and
income.
Under
the
base
model,
nitrogen
use
of
up
to
150
pounds
per
acre
is
allowed,
but
less
acreage
is
devoted
to
corn
pro-
duction,
whereas,
under
the
combined
soil
loss
and
nitrogen
use
restriction,
more
acreage
is
devoted
to
corn
production.
FARM
LEVEL
IMPACTS
Data
on
net
incomes
and
soil
losses
at
the
indi-
vidual
farm
levels
resulting
from
the
imposition
of
soil
loss
and
nitrogen
use
restrictions
are
summa-
8
The
93
-dollar
-per
-acre
average
income
figure
is
found
by
dividing
the
watershed
net
income
($199,054)
by
the
watersheds'
acreage
(2,135).
9
This
is
shown
by
a
comparison
of
footnote
"e"
in
table
2
and
in
table
3.
TABLE
2.
Watershed
model
results
by
individual
farm
and
nine
-farm
total
with
nitrogen
application
rates
of
50,
100,
or
150
pounds
per
acre
and
no
soil
-loss
restrictions
(Period:
1
to
10
years)
Crop
Activities
Tillage
Practices
Conservation
Practices
z
Row
-crop
(acres)
Two
-crop
(acres)
Wheat
Wheat
(acres)
Total
SGM
b
Pasture
(acres)
(acres)
Conven-
tional
(acres)
Zero
tillage
(acres)
Up
and
down
tillage
(acres)
Contour-
ing
(acres)
Terrac-
ing
(acres)
NET
REVENUE
c
(dollars)
TOTAL
SOIL
LOSS
(tons)
TOTAL
d
N/FARM
(pounds)
1
188
111 111 111
77
111
169
19
$21,732
4,169
12,918
2
186
186
186
27,242
2,753
27,885
3
152
79
79
83
77
79
128
13
16
16,126
3,824
11,161
4
160
143
143
145
134
19
143
143
11
8
20,083
3,446
3,968
5
184
99 99
106
14
93
99
149
43
20,284
3,463
12,575
6
366
129 129
165
31
273
129
233
14
154
38,157
6,350
30,836
7
177
127
127
144
74
66
127 127
66
20,523
3,811
5,730
8
217
203
203
206
68
16
203
210
9
25,913
4,879
4,161
9
75
48
48
57
33
36
48
48
36
8,994
1,270
2,826
Total
1,705
e
939
939
1,017
f
354
843
939
1,393
57
332
$199,054
33,965
112,060
a
Two-crop
denotes
the
double
-cropping
option
of
wheat
and
soybeans
of
rotation
5.
b
SGM
denotes
small
grain
(wheat
and
oats)
and
meadow.
c
The
net
revenue
values
are
annual
averages
for
the
ten-year
period
discounted.
d
Some
acreage
uses
no
nitrogen
and
some
rotations
use
very
little
nitrogen.
f
Components
are
corn,
688.1;
and
soybeans,
1,015.75.
Components
are
wheat,
938.4;
and
oats,
77.35.
NORTH
CENTRAL
JOURNAL
OF
AGRICULTURAL
ECONOMICS,
Vol.
1,
No.
2,
July
1979
TABLE
3.
Watershed
model
results
by
individual
farm
and
nine
-farm
total
with
soil
losses
restricted
to
SCS
tolerance
limits
on
a
per
-farm
basis
(Period:
1
to
10
years)
Crop
Activities
Tillage
Practices
Conservation
Practices
o
z
<
1.L.
NET
REVENUE
c
(dollars)
TOTAL
SOIL
LOSS
(tons)
TOTAL
d
N/FARM
(pounds)
Row
-crop
(acres)
Two
-crop
s
Wheat
(acres)
(acres)
Total
SGM
b
Pasture
(acres)
(acres)
Conven-
Zero
Up
and
down
tional
tillage
tillage
(acres)
(acres) (acres)
Contour-
ing
(acres)
Terrac-
ing
(acres)
1
120
21
68
188
106
81
$18,902
637
13,916
2
176
1
10
186
146
40
26,793
902
26,096
3
118
7
34
156
58
98
15,014
654
13,827
4
69
30
93
134
162
126
36
16,117
1,050
5,835
5
143
9
49
14
192
78
114
18,938
878
15,145
6
300
23
102
31
402
141
261
36,633
1,762
35,773
7
106
21
87
74
193
63
130
18,525
1,070
8,373
8
150
18
70
68
219
107
113
23,117
1,148
10,984
9
41
15
43
33
84
42
42
7,897
467
2,609
Total
1,223
e
145
556
f
354
1,782
867
915
$181,936
8,568
132,558
a
Two-crop
denotes
the
double
-cropping
option
of
wheat
and
soybeans
of
rotation
5.
b
SGM
denotes
small
grain
(wheat
and
oats)
and
meadow.
c
The
net
revenue
values
are
annual
averages
for
the
ten-year
period
discounted.
d
Some
acreage
uses
no
nitrogen
and
some
rotations
use
very
little
nitrogen.
f
Components
are
corn,
1,026.79;
and
soybeans,
199.57.
Components
are
wheat;
147.15;
oats,
158.17;
and
meadow,
249.52.
ANALYSIS
OF
SOIL
EROSION
CONTROL,
Nelson
and
Seitz
177
TABLE
4.
Watershed
model
results
by
individual
farm
and
nine
-farm
total
with
soil
loss
constrained
to
SCS
tolerance
limits
on
a
per
-farm
basis
and
nitrogen
application
rates
restricted
to
50
or
100
pounds
per
acre
(Period:
1
to
10
years)
a
Crop
Activities
Tillage
Practices
Conservation
Practices
NET
REVENUEc
(dollars)
TOTAL
SOIL
LOSS
(tons)
TOTAL
A
N
/
F
A
R
W
(pounds)
Row
-crop
(acres)
Two-crop
a
(acres)
Wheat
(acres)
Total
SGM
b
Pasture
(acres)
(acres)
Conven-
tional
(acres)
Zero
till
ag
e
(acres)
Up
and
down
till
age
(acres)
Contour-
i
ng
(acres)
Terrac-
i
ng
(acres)
1
111
21
76
188
106
81
18,607
637
8,328
2
145
22
22
63
164
22 22
124
40
25,203
902
10,779
3
107
5
49
156
58
98
14,771
654
7,910
4
67
30
95
134
162
126
36
16,091
1,050
4,526
5
133
7
59
14
192
78
114
18,731
878
10,803
6
264
19
138
31
402
141
261
35,953
1,762
19,638
7
106
21
87
74
193
63
130
18,526
1,070
8,373
8
149
18
71
68
219
107
113
23,075
1,148
10,253
9
41
15
43
33
84
42
42
7,897
467
2,609
f
Total
1,123
e
22
158
681
354
1,760
22
22
845
915
178,854
8,568
83,219
a
Two-crop
denotes
the
double
-cropping
option
of
wheat
and
soybea
ns
of
r
ot
a
ti
on
5.
b
SGM
denotes
small
grain
(wheat
and
oats)
and
meadow.
c
The
net
revenue
values
are
annual
averages
for
the
ten-year
period
discounted.
Some
acreage
uses
no
nitrogen
and
some
rotations
use
very
little
n
it
r
o
gen
.
f
Components
are
corn,
764.61;
and
soybeans,
357.32.
Components
are
wheat,
157.24;
oats,
294.82;
and
meadow,
229.60.
NORTH
CENTRAL
JOURNAL
OF
AGRICULTURAL
ECONOMICS,
Vol.
1,
No.
2,
July
1979
TABLE
5.
Watershed
model
results
by
individual
farm
and
nine
-farm
total
with
soil
loss
constrained
to
SCS
tolerance
limits
on
a
per
-farm
basis
and
nitrogen
application
rates
restricted
to
50
pounds
per
acre
(Period:
1
to
10
years)
Crop
Actiilities
Tillage
Practices
Conservation
Practices
a
LL.
Row
-crop
(acres)
Two-crop
a
(acres)
Wheat
(acres)
Total
SGM
b
Past
u
re
(acres)
(acres)
Conven-
ti
o
n
a
l
(acres)
Zero
till
age
(acres)
Up
and
down
t
ill
age
(acres)
Contour-
i
ng
(acres)
Terrac-
i
ng
(acres)
NET
REVENUEc
(dollars)
TOTAL
SOIL
LOSS
(tons)
TOTAL
d
N/
F
ARM
(pounds)
1
109
28
78
188
106
81
18,160
637
4,840
2
139
47
186
24
123
40
24,336
902
5,809
3
104
7
25
59
149
7
7
51
98
14,168
654
4,165
4
65
35
96
134
162
126
36
15,948
1,050
3,519
5
125
18
42
85
14
174
18
18
59
114
17,780
878
4,840
6
254
24
63
171
31
378
24
24
117
261
34,597
1,762
10,518
7
110
7
45
90
74
187
7 7
55
130
17,993
1,070
4,595
8
143
34
70
110
68
186
34
34
73
113
22,573
1,148
5,047
9
46
17
38
33
84
42
42
7,864
467
2,007
f
Total
1,095
e
90
325
774
354
1,694
90
114
752
915
173,419
8,568
45,340
a
b
Two-crop
denotes
the
double
-cropping
of
wheat
and
soybeans
of
rotation
5.
c
SGM
denotes
small
grain
(wheat
and
oats)
and
meadow.
d
The
net
revenue
values
are
annual
averages
for
the
ten-year
period
discounted.
Some
acreage
uses
no
nitrogen
and
some
rotations
use
very
little
nitrogen.
e
Components
are
corn,
693.78;
and
soybeans,
401.56.
f
Components
are
wheat,
324.62;
oats,
145.98;
and
meadow,
304.29.
ANALYSIS
OF
SOIL
EROSION
CONTROL,
Nelson
and
Seitz
179
180
NORTH
CENTRAL
JOURNAL
OF
AGRICULTURAL
ECONOMICS,
Vol.
1,
No.
2,
July
1979
Farm
-Based
SCS
"T"
100
Limits
95
90
Net
Income
As
A
Percent
of
Benchmark
Solution
Income
85
80
Farm
-Based
SCS
"T"
100
Limits
and
N
<
100
95
90
85
80
Farm
-Based
SCS
"T"
100
--
Limits
and
N
<
50
95
90
85
MEM
0
--
Watershed
I
1
2
3
4
5
6
7
8
9
Farm
Number
Figure
1.
Net
income
as
a
percent
of
benchmark
income
by
farm.
rized
graphically
in
figures
1
and
2.
One
result
that
appears
to
be
important
is
the
substantial
variation
in
the
impact
of
the
different
policies
on
different
farm
incomes.
For
example,
farm
number
2,
the
fl
atest
and
most
productive,
realizes
very
small
re-
ductions
in
net
income
while
farm
number
4,
the
farm
with
the
most
steeply
sloping
land,
experi-
ences
the
greater
net
income
reductions.
This
vari-
ation
in
net
incomes
between
individual
farms
upon
which
restrictions
are
imposed
stems
from
differences
in
erodability
and
productivity
of
the
farm
soil.
Data
presented
in
figure
2
indicate
that
soil
losses
on
individual
farms
range
from
a
high
of
about
25
tons
per
acre
on
farm
number
3
to
a
low
of
about
14
tons
per
acre
on
farm
number
2.
It
is
significant
that
a
policy
of
short
-run
profit
maxi-
mization,
the
benchmark
solution,
results
in
an
annual
average
soil
loss
per
acre
on
farm
number
3
five
times
greater
than
the
maximum
the
Soil
Con-
servation
Service
recommends
for
the
nation's
best
soils.
The
25
tons
per
acre
soil
loss
is
more
than
five
times
the
soil
loss
recommended
for
the
farm
ANALYSIS
OF
SOIL
EROSION
CONTROL,
Nelson
and
Seitz
181
Soil
Loss
(tons/acre/year)
Loss
(tons/acre/year)
5.0
4.5
4.0
26
24N.-
22
20-
18-
16
Farm
-Based
SCS
"T"
Limits
Benchmark
Solution
—..
,IMMinliMmolin
14
Watershed
1
2
3
4
5
6
7
8
9
Farm
Number
Figure
2.
Average
soil
loss
per
acre
year
by
farm.
following
SCS
soil
loss
tolerances.
1
°
It
is
also
interesting
that,
while
farm
number
2,
the
fl
atest
and
most
productive,
has
the
lowest
soil
loss
under
the
benchmark
solution,
it
has
the
highest
soil
loss
under
the
tolerance
limit
constraint.
This
reflects
the
higher
tolerance
limits
on
productive
soils
and
the
maximum
utilization
of
these
soils
in
this
model
solution.
LONG-TERM
ANALYSIS
This
section
examines
the
long-term
dimen-
sions
of
soil
erosion
control.
A
linear
programming
10
SCS
tolerances
are
defined
as
"the
maximum
amount
of
soil
loss,
in
tons
per
acre
per
year,
that
can
be
tolerated
while
allowing
for
sustained
economic
production
in
the
forseeable
future
with
present
technology."
Generally,
SCS
has
established
soil
loss
tolerances
ranging
from
one
to
five
tons
per
acre
per
year.
For
further
details
see
Schertz
and
Clark
[7,
p.
31.
model
of
one
hundred
years,
in
subperiods
of
ten
years,
was
used
to
analyze
the
potential
long
-run
impacts
of
soil
erosion
control.
The
objective
func-
tion
maximized
is
annualized
income
above
total
costs
for
a
ten-year
period,
discounted
at
5
per-
cent.
Series
of
ten
ten-year
planning
periods
are
considered
to
generate
the
one
-hundred
-year
anal-
ysis.
In
any
given
ten-year
period
the
objective
function
values
are
weighted
by
the
makeup
of
the
rotations
that
enter
the
solution.
Initial
soil
depths
in
inches
of
each
soil
type
slope
-erosion
class
were
estimated
and
placed
with-
in
the
model.
These
data
were
adjusted
by
gross
erosion
losses
after
each
ten-year
period
using
a
FORTRAN
model
[4,
p.
10].
Gross
soil
loss
esti-
mates
in
tons
per
acre
are
converted
to
acre
-inch
figures
based
on
bulk
density
data.
The
adjust-
ments
in
yields,
necessitated
by
soil
loss
over
time
are
achieved
by
modifying
the
adjustments
for
soil
182
NORTH
CENTRAL
JOURNAL
OF
AGRICULTURAL
ECONOMICS,
Vol.
1,
No.
2,
July
1979
200
190
180
170
160
150
140
130
2
120
110
100
90
80
••••••
70
~NI
Assumptions
1.
Production
Under
SCS
60
Plomm•
Tolerance
Limits,
Discounted
0%
2.
Unconstrained,
Discounted
0%
50
.1011110
Pasture
Production
On
Eroded
Soil
3.
Unconstrained,
Discounted
0%,
No
40
'NMI&
Production
On
Eroded
Soil
4.
Same
As
1,
Discounted
5%
30
5.
Same
As
2,
Discounted
5%
6.
Same
As
3,
Discounted
5%
20
1•1•1111M
10
6
0
I
1
1
1
I
0
10
20
30
40
50
60
70
80
90
100
Time
(years)
Figure
3.
Net
watershed
income
for
an
average
year
by
ten-year
periods
for
100
years.
ANALYSIS
OF
SOIL
EROSION
CONTROL,
Nelson
and
Seitz
183
In
0
Cumulative
Net
Watershed
Income
(mil.
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
0
SCS
Tolerance
Limits,
Not
Discounted
Unconstrained,
Not
Discounted
Unconstrained,
Discounted
SCS
Tolerance
Limits,
Discounted
I
I
1
10
20
30
40
50
60
Time
(years)
I I
I
I
70
80
90
100
Figure
4.
Cumulative
net
watershed
income
over
ten-year
periods
for
100
years.
erosion
and
slope
suggested
by
Odell
and
Oschwald
[6,
p.
12;
5,
p.
90].
This
procedure
is
followed
until
the
topsoil
is
completely
eroded
on
a
given
slope
type.
If
topsoil
is
completely
eroded,
one
of
two
assumptions
is
made:
Either
production
ceases,
or
the
soil
can
support
pasture
and/or
woodland
production
at
reduced
yields
[5,
p.
90]
.
11
11
This
analysis
does
not
consider
soil
formation,
which
will
likely
be
minimal
in
the
100
-year
period.
On
some
subsoils
it
is
possible
to
continue
production
after
topsoil
erosion
at
higher
costs
by
substituting
plant
nutrients
and
adding
organic
matter.
Figure
3
graphically
presents
two
sets
of
data
from
the
long
-run
analysis
of
the
watershed
area.
In
one
case
it
is
assumed
that
pasture
and/or
wood-
land
production
is
possible
at
reduced
yields
on
completely
eroded
soils.
In
the
other
case
it
is
assumed
that
no
economical
production
is
possible.
Figure
3
indicates
that
incomes
are
higher
when
restrictions
are
not
present
than
are
those
incomes
generated
subject
to
Soil
Conservation
Service
recommendations
during
the
early
years.
However,
after
the
interval
of
thirty-one
to
forty
years,
in-
comes
generated
subject
to
SCS
recommendations
are
substantially
greater
than
those
with
the
un-
184
NORTH
CENTRAL
JOURNAL
OF
AGRICULTURAL
ECONOMICS,
Vol.
1,
No.
2,
July
1979
(1000
dollars)
U
E
U
Cumulative
Net
Farm
1.
SCS
Tolerance
Limits,
Undiscounted,
Farm
No.
2
2.
Unconstrained,
Undiscounted,
Farm
No.
2
3.
SCS
Tolerance
Limits,
Farm
4
280--
Undiscounted,
No.
260
240
220
4.
Unconstrained,
Undiscounted,
Farm
No.
4
1
200
1111•10M•
180
160
MIMM•10
140
120
Imam.
100
11•11110•10
80
60
40
20
ima
to
0
1
0
10
20
30
40
50
60
70
80
90
100
Time
(years)
Figure
5.
Cumulative
and
undiscounted
net
farm
income
(farms
no.
2
and
no.
4)
over
ten-year
periods
for
100
years.
restricted
soil
loss
policy.
The
magnitude
of
the
differences
is
somewhat
less
when
these
incomes
are
discounted,
but
the
same
trends
exist.
Figure
4
presents
cumulative
discounted
and
undiscounted
net
incomes
under
SCS
soil
loss
recommendations
and
those
with
unconstrained
soil
loss,
assuming
that
no
production
takes
place
after
all
topsoil
has
eroded.
The
undiscounted
cumulative
curves
show
that
unconstrained
or
unrestricted
soil
losses
result
in
greater
net
in-
ANALYSIS
OF
SOIL
EROSION
CONTROL,
Nelson
and
Seitz
185
comes
through
approximately
the
forty
-year
period,
after
which
net
incomes
generated
subject
to
SCS
soil
loss
recommendations
are
greater.
When
these
incomes
are
discounted
at
5
percent,
income
estimates
with
SCS
soil
loss
recom-
mendations
are
slightly
lower
than
those
with
the
unrestricted
policy
up
to
about
forty
years.
After
this
point,
net
incomes
are
higher
with
constrained
soil
losses.
However,
the
cumulative
total
incomes
for
the
restricted
and
unrestricted
soil
loss
policies
over
the
one
-hundred
-year
period
are
about
equal.
This
results
primarily
from
a
combination
of
the
discount
rate
and
greater
incomes
in
the
initial
years
in
the
unconstrained
policy,
which
largely
balances
the
greater
incomes
with
SCS
soil
loss
restrictions
in
later
years.
Data
presented
in
figures
3
and
4
on
the
water-
shed
area
do
not
indicate
how
the
income
impacts
of
soil
loss
restrictions
differ
among
individual
pro-
ducers.
These
data
also
fail
to
indicate
if
and
when
individual
producers
will
break
even
under
con-
strained
and
unconstrained
policies.
Data
presented
in
figure
5
give
cumulative
income
patterns
for
two
farms
over
the
one
-hundred
-year
period.
These
data
show
that
the
income
of
farm
number
2
will
not
be
severely
reduced
if
soil
loss
constraints
are
imposed.
However,
if
soil
loss
limitations
are
im-
posed
on
farms
of
soil
type
makeup
steeply
slop-
ing
land
similar
to
farm
number
4,
incomes
would
be
severely
impacted.
These
data
further
show
that
farm
number
2,
which
includes
the
most
flat
and
productive
land,
would
break
even
(equal
cumulative
incomes
with
the
two
policies)
around
year
thirty.
Farm
number
4
data,
however,
show
that
it
takes
about
ninety-five
years
before
the
cumulative
incomes
are
equal
under
the
two
poli-
cies.
It
should
be
recognized
that
these
estimated
impacts
may
change
substantially
if
we
consider
the
aggregate
price
and
quantity
effects
which
may
result
if
soil
loss
and
nitrogen
use
restriction
policy
is
developed
for
the
nation
or
major
agricultural
production
regions.
A
Corn
Belt
study
utilizing
a
linear
programming
model
with
similar
nitrogen
use
and
soil
loss
restrictions
results
shows
that
pro-
ducers
would
gain
with
per
acre
soil
loss
and
nitro-
gen
use
restrictions
[11,
p.
28;
8,
p.
200]
.
This
gain
is
significantly
influenced
by
the
fact
that
the
estimated
price
and
quantity
changes
occurred,
to
a
large
extent,
in
the
inelastic
portion
of
the
de-
mand
curve
for
corn
and
soybeans.
Thus
per
acre
soil
loss
and
nitrogen
fertilizer
restrictions,
which
would
be
to
the
disadvantage
of
an
individual
pro-
ducer
if
imposed
only
on
his
farm,
would
be
to
his
advantage
if
imposed
in
a
large
region.
CONCLUSIONS
This
article
presents
results
of
an
analysis
of
the
effects
of
alternative
soil
erosion
control
poli-
cies
at
the
watershed
and
farm
level
for
part
of
the
Corn
Belt.
In
general
the
following
conclusions
can
be
drawn
from
the
results
of
this
analysis:
(1)
im-
posing
soil
loss
restrictions
will
impact
most
farms
but
will
have
different
impacts
on
net
incomes
among
farms
of
different
soil
types;
(2)
cumulative
discounted
incomes
over
the
one
-hundred
-year
period
for
the
watershed
with
or
without
soil
loss
restrictions
are
about
equal;
(3)
cumulative
dis-
counted
incomes
on
some
farms
subject
to
soil
loss
restrictions
will
be
below
those
of
farms
with
no
soil
loss
policy
and
would
not
reach
a
breakeven
point
regardless
of
the
length
of
planning
period;
(4)
per
acre
soil
losses
would
be
substantially
re-
duced
if
soil
loss
restrictions
were
instituted
based
on
SCS
recommendations;
and
(5)
the
model
sug-
gests
that
adoption
of
procedures
and
practices
to
control
nitrogen
use
and
soil
losses
will
not
be
undertaken
without
further
incentives.
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