United States
Environmental Protection
Agency
Municipal Environmental Research ^
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-83-113 Feb. 1984
Project Summary
Effects of Using Sewage Sludge
on Agricultural and Disturbed
Lands
T.D. Hinesly, LG. Hansen, and G.K. Dotson
A series of studies was conducted to
determine the effects of using sewage
sludge on agricultural and disturbed
lands. The studies included examina-
tions of soils, drainage water, runoff,
and crops from both field and lysimeter
plots treated with digested sewage
sludge from Chicago. In addition,
several special studies were conducted
to compare metal uptake in various corn
inbred hybrids. Further studies were
conducted to assess the effects of
certain sludge constituents on animals
that consume plants grown on sludge-
amended soils.
Forty-four lysimeters were construc-
ted (3.1 x 15.25 m) with three signifi-
cantly different soils types — Elliott silt
loam (10 lysimeters), Plainfield sand
(10 lysimeters), and Blount silt loam (24
lysimeters). Field plots were all Blount
silt loam and measured 6.1 x 12.2 m.
Digested municipal sewage sludge
from Chicago was applied tcrboth types
of plots annually, first by overhead
sprinklers and later by furrow irrigation.
Applications were made for 8 years on
the lysimeter plots and 10 years on the
field plots. Drainage and runoff samples
were analyzed for fecal colrforms. NH«-IM,
P. K, Na, Zn. Cu, Ni. Cd, Cr, Pb, Fe, Mn,
Se, As, Se, Hg, total solids, and organic
carbon.
Corn and soybean crops grown on the
plots were analyzed for yield, metals, N,
and P. Sludge samples were also taken
and analyzed at every application.
Runoff and drainage waters from
sludge-treated lysimeter plots often
had slightly higher concentrations of
NH4-N, NC-3-N, P, K, Na, Zn, Cu, Ni, Cd,
Cr, total solids, organic carbon, and
electrical conductivities than did similar
samples from the control plots. Concen-
trations of NOs were increased markedly
in drainage water. Soil concentrations
of several chemical elements also
increased, but the P-toxicrty in soybeans
was the only phytotoxic condition
produced by excessive sludge loading
rates applied each year. Metal concen-
trations in corn and soybean tissues,
and especially in corn grain, decreased
rapidly after sludge applications were
terminated. Soil type had no significant
effects on metal uptake by com.
Testing of inbred corn lines and their
progeny suggested that metal uptake
could be controlled through plant
breeding. These tests also showed that
major portions of Cd and other inorganic
elements were contained in the grain
fractions used as animal feed.
Applying sludge each year for 1O
years on continuous com plots improved
the physical properties of the soil and
never adversely affected seed germina-
tion. Sludge application to soil appeared
to have no deleterious effects on micro-
bial populations or enzyme activity in
the soil.
No adverse health or performance
effects were observed in the pheasants
and swine that were fed crops from
sludge-amended soils.
This Project Summary was developed
by EPA's Municipal Environmental
Research Laboratory, Cincinnati. OH, to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
Project Report ordering information at
back).
-------
Introduction
Digested sewage sludge is an effective
source of both nitrogen and phosphorus
for the fertilization of growing crops.
When sludge is applied by ridge and
furrow irrigation, crop yields are equal to
or greater than those obtained with
inorganic fertilizers applied at rates ade-
quate for maximum yields. But concern
exists over the possible uptake of metals
by food crops and their subsequent
effects on human health. For example, if
cadmium levels in food are sufficiently
elevated, it is conceivable that this metal
will accumulate in kidneys and eventually
create chronic illness.
This study was conducted to determine
the effects of using sewage sludge on
agricultural and disturbed lands. The
project included examinations of soils,
drainage water, runoff, and crops from
both field and lysimeter plots treated with
digested sewage sludge from Chicago.
Special studies were also conducted to
assess the effects of certain sludge
constituents on animals that consume
plants grown on sludge-amended soils.
Municipal sewage sludge was applied
annually to lysimeter and field plots at
variable rates. The 3.1- by 15.25-m
lysimeter plots and the 6.1- by 12.2-m
field plots represented three soil types
and received sludge applications for 8
and 10 years, respectively. The maximum
application rate was approximately equal
to the amount of sludge needed to supply
ten times the nitrogen required for an
optimum corn yield. The other rates were
equal to one-half and one-fourth of the
maximum rate. Corn and soybeans were
grown on both lysimeter and field plots.
Digested sewage sludge from Chicago
was applied to all plots, first by overhead
sprinklers, and later by furrow irrigation.
Water samples were analyzed for fecal
coliforms, NHU-N, P, K, Na, Zn, Cu, Ni, Cd,
Cr, Pb, Fe, Mn, Se, As, Se, Hg, total solids,
and organic C. Soil samples were
collected from 15-cm deep increments
annually after plowing and before sludge
addition. They were analyzed for total and
available metals and nutrients. Soil pH
and organic C content were also deter-
mined. Sludge samples were taken and
analyzed each time an application to soil
was made. Corn leaves, grain, and stover
were sampled and analyzed for metals, N,
and P.
Long-term field plot studies involved
variable rates of liquid digested sludges
applied in the same manner, as on the
lysimeter plots. The soil was Blount silt
loam and the crops were corn, soybeans,
and wheat. Plants were analyzed for yield
and composition, and soils were analyzed
annually, as in lysimeter studies.
A special study was conducted to
compare the heavy metal and P uptake by
corn inbred lines and hybrid crosses from
selected inbred lines.
To assess the effects of some of the
chemical elements in sludge on the
health, performance, and composition of
animals that consume the plants grown
on sludge-amended soils, crops were fed
to pheasants and swine.
Lysimeter Studies
Procedures
Beginning in 1969, sludge from high-
rate anaerobic digesters at the Calumet
and Stickney wastewater treatment
plants near Chicago was applied by
irrigation to 44 lysimeter plots measuring
3.1 by 15.25 m. The lysimeter installation
was located on a small watershed at the
Northeast Agronomy Research Center
near Elwood, Illinois.
The lysimeters contained three signifi-
cantly different soil types. Elliott silt loam
was simulated in 10 lysimeters by
removing the surface 31 cm of Blount silt
loam and replacing it with the surface of
Elliott. Plainfield sand was simulated in
10 lysimeters by excavating the Blount
silt loam to a depth of 1.52 m and
replacing it with sand from a Plainfield
soil. Blount silt loam occupied the
remaining 24 lysimeters.
Tile drains were installed through the
center of each lysimeter plot, and a
fiberglass trough was installed at the
downslope end of each plot to collect
runoff. Both drainage water and runoff
were conveyed separately through PVC
pipes from the plots by gravity to the
basement of an instrument house. Tip-
ping bucket equipment was provided to
measure rates and total volume of flows
from each of the PVC pipes. Automated
sampling equipment was provided for each
of the PVC pipes, and for the most part,
a 400 ml sample was collected from the
second tip of a tipping bucket and again
on each sequential 42nd tip of a bucket
thereafter for the duration of a flow
event.
Sprinkler irrigation was used to apply
sludge during the first two years, after
which a furrow system of irrigation was
used. Sludge was applied at rates equal to
depths of 6.4,12.7, and 25.4 mm. Control
plots were irrigated with 25.4 mm of well
water on the same day sludge applications
were made. All plots were fertilized with
KCI to supply 134 kg K/ha before the
preparation of seedbeds. Control plots (no
liquid sludge) received fertilizer applica-
tions of 268 kg N/ha and 134 kg P/ha as
NH4N03 and superphosphates. Fertilizer,
liquid sludge, and water applications
were terminated on all Blount silt loam
plots in the north series at the end of the
1973 growing season. Applications of
sludge at less than maximum rates were
also discontinued on Elliott silt loam and
Plainfield loamy sand plots in the north
series. But sludge applications were
continued on all plots representing these
two soil types in the south series until the
end of the 1976 growing season. After
1976, sludge was applied only on Blount
silt loam plots in the south series.
Amounts of sludge solids and other
constituents applied annually to maxi-
mum-treated plots are listed in Table 1.
Appropriately lesser amounts from a
particular tank of sludge were applied to
plots treated with one-fourth and one-
half the maximum. Amounts of sludge-
borne constituents varied from one year
to the next because of differences in
sludge solids content and weather condi-
tions that controlled the number of
applications.
Concentrations of several sludge
constituents were monitored in drainage
and runoff water from the time the study
was initiated. Beginning in 1976, water
samples were analyzed for Se, As, Sb,
and Hg, even though concentrations of
these elements in sludges were relatively
low.
Results
Changes in Water Quality
The geometric means of data from
sludge-treated plots were compared with
those from control plots to determine
possible significant differences in water
quality resulting from sludge treatment.
Concentrations of Zn, Cd, and Cu in
runoff and drainage water were either
unaffected by sludge applications or were
increased regardless of soil type. But the
significant increases in concentrations of
these three metals were so low that
differences resulting from treatment
probably could not have been detected in
the absence of the extensive water
sampling program that was conducted
during this study. Not enough data have
been collected to assess adequately the
effects of sludge applications on concen-
trations of Ni, Cr, Pb, Se, As, Sb, and Hg.
The data that have been obtained
indicated that only Ni and Cr concentra-
tions in effluent waters from sludge-
treated sites may be increased slightly.
Annual sludge applications over an 8-
year period did not appear to have
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Table 1.
Series
and
year
Amounts (Dry Wtj of Sludge Constituents Applied Annually to Maximum-Treated Plots ofBlount Silt Loam, Elliott Silt Loam, and Plainfield
Loamy Sand Lysimeter Plots*
Metric tons kg/ha
of Total
solids/ha N P K Na Ca Mg Fe Mn Zn Cd Cu Ni Cr Pb
North series:
1969
1970
1971
1972
1973
1974
1975
1976
South series:
16.4
52.8
57.8
44.4
61.1
69.8
54.0
72.0
1134
2902
3532
2292
3286
4933
3367
3989
819
2067
1984 535
1174 252
2000 359
2717 361
1681 343
2343 403
246
204
414
284
207
269
448
1361
2062
2248
2770
2055
1641
1992
243
821
546
545
653
722
677
858
860
2734
2526
1825
2067
3190
2607
3301
5
17
17
21
32
30
26
40
158
427
265
192
248
359
245
273
7.9 36
22.6 101
13.2 69
7.8 33
6.8 41
21.8 117
13.4 85
19.2 127
10.7
22.1
15.6
4.3
5.2
24.2
21.3
32.1
102 23
266 100
161 71
54 46
87 55
210 65
170 60
219 66
1969
1970
1971
1972
1973
1974
1975
1976
19.3
36.2
104.7
32.2
58.8
70.7
52.4
71.3
813
2329
3636
1650
3202
4803
3367
4604
805
1187
3010
943
1796
2663
1681
2412
963
168
370
357
343
396
395
186
379
291
207
248
399
989
3287
1342
2831
1868
1641
1987
190
570
876
414
653
725
677
870
455
1723
3967
1239
2041
3339
2607
3301
4
10
25
14
31
37
26
45
122
312
464
135
224
350
245
273
5.2
22.2
24.0
5.8
6.7
21.7
13.4
19.1
27
69
114
22
38
114
85
115
7.7
14.5
28.2
3.1
7.6
22.6
21.3
30.9
79
174
298
40
76
205
170
226
14
100
124
30
52
75
60
66
* After the 1973 growing season, sludge applications were terminated on all plots in the north series except for maximum-treated Elliott silt loam and
Plainfield loamy sand plots.
affected concentrations of Pb, Se, As, Sb,
and Hg in runoff or drainage water
samples collected in 1976 and 1977.
During the last 6 years of the study, no
evidence was found that any measured
water quality parameter was deteriora-
ting with increased years of annual
sludge applications. Also noteworthy
(especially with regard to P and heavy
metals) is that sludge-amended Plainfield
loamy sands yielded about the same
concentrations of various elements in
their drainage waters as did the sludge-
treated Blount and Elliott silt loams.
Surface runoff and drainage water
samples from the lysimeter plots were
tested for fecal coliforms by the membrane
filter method within 36 hr of collection.
Concentrations in drainage waters from
the three soils types varied widely
between seasons. Differences between
fecal coliform levels of drainage water
from the silt loam soils and Plainfield
loamy sand plots are evident in all
seasons. The Plainfield loamy sand plots
consistently yielded lower concentrations
than the finer Blount and Elliott soils. In
general, comparisons of untreated and
maximum-sludge-treated plots show
only a slight increase in coliform counts
in the latter.
Soils
Compared with normal soils, those
treated with digested sewage sludge
contained relatively high levels of Zn, Cd,
Cu, Ni, Cr, and Pb. Except for Ni, levels of
all of these metals were significantly
higher in the surface of soils given
maximum sludge treatments. Because of
large variations in soil sample contents,
Ni concentrations in maximum-sludge-
treated soil surfaces were not always
higher than those in control plots. Except
for Ni, total concentrations of all metals
remained unchanged in the soil below
the surface plow layer regardless of
sludge application rates and soil type.
Surface soil pH of maximum-sludge-
treated Blount silt loam plots was
significantly lower than that of control
plots during the last year in the north
series and during the last 2 years for
those in the south series.
Grain Yields
Before 1974, grain yields on north
Blount plots were not affected by the rate
of annual sludge applications. But yields
increased during the second, third, and
fourth years after termination of sludge
treatment. Blount silt loam plots in the
south series that received one-fourth and
one-half the maximum sludge treatments
produced less corn grain in 1971 and
1974 than did the irrigated control plots.
On the other hand, yields from Blount silt
loam maximum-sludge-treated plots
were not significantly different from
those produced on control plots—except
in 1975, in the south series. For this one
year, grain yields were lower on maxi-
mum-sludge-treated plots (P<0.05) than
on irrigated control plots. But stover
yields from the same maximum-sludge-
treated plots were the highest ever pro-
duced during the study, regardless of
treatment.
Metal Uptake in Plants
Zinc concentrations were increased in
all plant tissues by annual sludge
applications. Where sludge applications
were terminated after 1973 (Blount silt
loam in the north series), Zn concentra-
tions in grain and stover from treated and
control plots were not significantly
different in 1976 and 1977. Zn concentra-
tions in leaves from those plots that had
previously received maximum sludge
treatments were significantly higher than
those in leaves from control plots during
1977, the last year of the study; but levels
were less than half those from the last
crop year affected by annual sludge
applications (1974).
Effects of sludge applications on Cd
contents were similar to those on Zn
concentrations. After sludge applications
were terminated (Blount silt loam, north
series, 1973), Cd concentrations in grain
from sludge-treated plots continued to be
significantly higher than in samples from
control plots. But in most years after
sludge applications were terminated, leaf
-------
and stover samples had Cd concentrations
that were two to six times less than in
years when applications were made
annually.
Field Plot Studies
Procedures
Four replications of 6.1 -by 12.2-m plots
with four sludge treatments randomized
within blocks were established in 1968
on Blount silt loam soil (Aerie ochraqualf,
fine, illitic, mesic) occupying part of the
cultivated area on the Northeast Agro-
nomy Research Center near Joliet,
Illinois. Digested sludge was first applied
by furrow irrigation in 1968 and an-
nually thereafter during the growing
season. An additional application was
sometimes made during the fall after the
grain harvest. All plots were annually
fertilized with a broadcast application of
KCI to supply 134 kg K/ha. Control plots
(no liquid sludge) were further treated
with annual broadcast fertilizer applica-
tions supplying 268 kg N/ha and 134 kg
P/ha. As often as weather conditions
permitted, liquid digested sludge was
transported by truck trailer tanks from the
Metropolitan Sanitary District of Greater
Chicago Southwest or the Calumet
wastewater treatment plants and applied
at liquid depths of 25.4 mm (maximum),
12.7 mm (one-half maximum), and 6.4
mm (one-fourth maximum) to each of the
appropriate plots on the same day.
Immediately after ridges and furrow
were established, corn (Zea mays L.) was
planted at rates calculated to give a plant
population of 60,000 plants/ha on top of
ridges spaced 76 cm apart. In general,
sludge was applied for the first time each
year when corn plants had reached a
height of about 15 cm.
Samples of sludge, soil, and plant
tissues were collected and analyzed by
the same methods and procedures
described in the earlier section on
lysimeter studies.
Annual and accumulated amounts of
liquid digested sludge applied in 1968-77
to maximum-treated plots are shown in
Table 2 along with the calculated dry
weights of solids applied. About 3,000,
700,180, and 140 kg/ha of Zn, Cu, Ni,and
Cd (respectively) were accumulatively
applied as constituents of sludge on
maximum-treated plots.
Results
Soils
Several chemical properties of Blount
silt loam were changed by sludge
applications. Changes in soil composition
Table 2. Annual Digested Sludge Loading Rates and Total Accumulations on Maximum-
Sludge-Treated Blount Silt Loam Plots Planted with Corn
Liquid sludge
applied (cm)
Year
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
Annual
17.1
25.4
22.9
38.1
12.7
27.9
17.8
12.7
17.8
15.2
Accumulation
17.1
42.5
65.4
103.5
116.2
144.1
161.9
174.6
192.4
207.6
Dry solids
applied Imt/ha)
Annual
51.62
48.31
52.67
128.37
25.61
62.15
48.72
32.56
54.44
52.29
Accumulation
51.52
99.83
152.50
280.87
306.48
368.63
417.35
449.91
504.35
556.64
were similar to those measured on soils
from lysimeter plots. Apparently, an
equilibrium condition between additions
and losses of N and C had been established
by 1974, and concentrations at equilibri-
um depended on annual loading rates.
Nothing indicated that total N and organic
carbon concentrations below 30 cm were
affected by sludge applications. Total P
concentrations were increased at both the
0- to 15-cm and 15- to 30-cm depths of
the soil by sludge applications.
Maximum and one-half maximum
sludge applications resulted in significant
corn grain yield increases in only 4 years
out of 10. But they never decreased
yields, and all sludge treatments resulted
in significantly higher 10-year average
grain yields than were produced with
high rates of conventional inorganic
fertilizers. The annual addition of large
amounts of sludge resulted in increased
concentrations of several elements in
corn grain, as shown in Table 3. Only Zn
and Cd were consistently increased in all
tissues tested.
Continuous Soybeans on Plots
of Blount Silt Loam
The main objective of this segment of
the study was to determine how soil
chemical changes produced by sludge
applications affect soybean nutrition and
chemical composition of plant tissues.
Three replications of 12.2- x 12.2-m
plots in a random complete block were
established on Blount silt loam in the fall
of 1968 for the following depth of
applications of liquid sludge: control
(zero); maximum (25.4 mm); one-half
maximum (12.7 mm); one-fourth maxi-
mum (6.4 mm). Well water was supplied
at the same time and rate as the
maximum sludge applications.
Only one application had been made in
1972 when the soybean seedlings on
maximum-sludge-treated plots began to
show symptoms of Ptoxicity. After severe
P toxicity symptoms were observed,
sludge applications were suspended until
harvesting was completed in 1973. When
P toxicity symptoms did not occur on
soybeans growing on maximum-sludge-
treated plots in 1973, sludge applications
were resumed on plots, that in previous
years had also received a broadcast
application of superphosphate, to deter-
mine whether P toxicity would recur.
Soybean yields were increased by
sludge application each year. Yield
depression in 1972 and 1976 on maxi-
mum-sludge-treated plots was attributed
to the P toxicity.
The concentrations of several elements
in soybeans were increased by sludge
application. Maximum sludge application
frequently resulted in higher concentra-
tions of N in leaves and petioles, but not in
beans and stalks. Phosphorus was
increased sometimes, but not in plants
from plots where sludge applications
were terminated in 1972. Concentrations
of Zn, Cd, and Ni were significantly
increased in all soybean tissues by
annual applications.
Mine Spoil Study
In the spring of 1973, a continuous
corn study was established on newly
graded strip-mine spoil banks in Fulton
County. For this study, sludge loading
rates, application methods, replication of
treatments, sample-collection and hand-
ling, etc., were similar to those in the
continuous study established in 1-968 on
the Northeast Agronomy Research Cen-
ter. The main difference between the two
studies was that the sludge used in
Fulton County was pumped from holding
reservoirs that stored the digested sludge
barged from the Southwest wastewater
treatment plant in Chicago. Major object-
ives of the study were (1) to assess the
value of sludge as opposed to convention-
al fertilizer for improving strip-mine
spoils for profitable rowcrop production,
and (2) to compare uptake of inorganic
elements by corn grown on sludge-
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TableS. Concentrations ofZn. Ni, Cu. andCdin Corn Grain from Sludge-Treated Field Plots on
Blount Silt Loam *, t
(ppm)
Sludge Treatment
Constituent Year
Zn 1970
1971
1972
1973
1974
1975
1976
1977
Ni 1970
1971
1972
1973
1974
1975
1976
1977
Cu 1970
1971
1972
1973
1974
1975
1976
1977
Cd 1970
1971
1972
1973
1974
1975
1976
1977
0
32
24
22
29
28
24
33
30
1.6
0.7
0.6
1.2
1.4
3.3
0.6
0.5
2.7
2.4
2.8
2.4
3.0
2.1
3.0
2.0
0.30
0.14
0.14
0.08
0.09
0.06
0.09
0.07
One-fourth
Maximum
40
37
29
37
37
36
42
43
1.6
1.2
0.8
0.9
1.6
3.2
0.6
0.4
3.7
2.6
3.0
2.6
3.1
2.1
2.5
2.2
0.60
0.70
O.45
0.15
0.18
0.17
0.26
0.25
One-half
Maximum
50
36
40
51
46
44
54
50
2.1
1.4
1.3
1.3
1.9
6.9
1.0
0.7
2.7
2.2
2.9
2.6
2.6
2.2
2.8
2.1
0.79
0.65
0.83
0.35
0.04
0.28
0.42
0.60
Maximum
65
53
50
58
56
53
62
62
3.1
4.0
2.2
1.7
2.0
5.9
1.6
2.0
2.9
2.0
3.1
2.0
2.2
2.0
3.2
2.4
1.00
0.92
1.10
0.61
0.81
0.51
0.84
0.92
Significant
Difference
/5J
70J
73J
6*
7*
6*
5J
9t
1.0%
1.7\
0.4\
0.4J.
0.4\
0.9t
0.4%
0.20J
0.40J
0.52J
0.06J
0.22\
o.osj
0. 73*
0.22J
"Concentrations are on a dry weight basis.
^Samples from plots identified in report as NW 8OO series.
^Significantly different at P < .01.
^Significantly different at P< .05.
amended-strip-mine silty clay loam with
corn grown on sludge-amended Blount
silt loam. Before plowing each spring,
336, 224, and 115 kg/ha of N, P, and K,
respectively, were applied to control
plots.
Maximum sludge applications produced
significantly higher yields of corn grain
than for the control plots in 3 of the 5 years,
and the 5-year mean yields were also
significantly higher. But the expected
increase in corn yields with increased
years of applying sludge did not occur,
perhaps because of excessive tillage
required to produce an adequate seed •
bed.
Except for Zn and Cd, sludge applica-
tions did not consistently produce signifi-
cant changes in concentrations of the
elements studied in corn tissues. Accu-
mulations of Zn and Cd in strip-mine spoil
appeared to affect tissue concentrations
much more than they did in plots of
Blount silt loam.
Special Studies
Uptake of Heavy Metals and P
by Inbred Corn Lines and
Crosses of Selected Inbred
Lines
This study was conducted to determine
differences in the accumulations of
selected elements in leaves and grain of
inbred corn grown on control plots and
sewage-sludge-amended soil.
Twenty inbred corn lines commonly
used as parents for hybrids adapted to the
Corn Belt were planted in Blount silt loam
(Aerie ochraqualf, fine illitic, mesic) with
and without sludge. At the beginning of
the 1976 growing season, maximum-
sludge-treated plots had received a 7-
year accumulative application of sludge
solids (374 metric tons/ha, dry weight
equivalent). During the growing season,
236 mm of sludge (71 metric tons/ha of
dry solids) were applied on maximum-
treated plots.
The six inbred lines in Table 4are listed
by Cd concentrations in grain from plants
grown on maximum-sludge-treated plots.
The results suggest that variations in P
and metal levels in corn leaves and grain
are determined by heritable differences
as well as by various concentrations
available in soils for plant uptake.
Effects of Sludge Applications
on Organic Fractions of Blount
Silt Loam Soil
This study was undertaken to gain
more precise information on the fate and
nature of the organic fraction of anaerobi-
cally digested sludge in the soil environ-
ment. The studies were carried out using
six Blount silt loam plots from the 44-plot
lysimeter facility. Soil samples were
collected in May 1975 to a depth of 76 cm.
Leachate water samples from the plots
were collected at the beginning of each
drainage event occurring from May 1974
through April 1975.
The most striking change in soil
composition resulting from sludge appli-
cation was the increase in oil and grease.
In the 0- to 15-cm depth, this fraction was
increased from 1.67% to 11.93% of the
total organic C. No poor growth resulting
from oxygen deficiency has been observed,
however, in these studies.
Biological Activity in Soils and
Strip-Mine Spoil With and
Without Sludge
When sludge from plants treating
industrial wastewaters are applied to
land, the ability of soil to bind heavy
metals and accumulate them in plant
rooting zones raises a serious question as
to the influence of the more soluble
metals on the biological activity in soils.
The purpose of this work was to determine
how the continuous heavy applications of
digested municipal sludge to cropland
affect the main systematic and physiolo-
gical groups of soil microflora and
enzymatic activity.
The data show consistent increases in
total bacterial populations with high
sludge application rates. In general, the
response of total bacteria to sludge
treatment at the maximum level was at
lease a twofold increase.
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Table 4. Concentrations of Cd in Grain from Inbred Corn Lines Grown on Control and Sludge-
Amended B/ount Silt Loam Plots *
fmg/kg)
Sludge application rates
Inbred
B37
H98
R802A
R177
AB73
R805
0
0.12
0.11
<0.06
0.16
0.09
0.06
Maximum
3.87
2.43
0.34
0.33
0.15
0.08
Least Significant
Difference
7.76f
o.srt
0./2f
0.1 4\
O.OSi.
n.s. §
* Concentrations are ranked from highest to lowest uptake by inbred lines grown on maximum-
sludge-treated plots.
t4 Significantly different at P < 0.05 and P < 0.07, respectively.
§ Not significantly different.
Except for Azotobacter, no clear-cut
evidence was found that microbial
populations and their activities were
restricted by sludge applications. The
most popular explanation for a decrease
in Azotobacter populations with higher
sludge application rates is that they are
unable to compete successfully with
other organisms in the presence of
abundant nutrient supplies.
Influence of Municipal Sewage
on Mineralization of Plant
Residues and Changes in
Microbial Populations
Heavy metals have been shown to affect
some microbiological processes in the
soil. The purpose of this study was to
determine the direct influence of metals
in sludge on the mineralization of plant
residues as compared with the indirect
influence of metals accumulated by
plants.
Based on data from the literature and
findings from this study, it appears that
the way metals affect the activity of
microorganisms depends on the form in
which the metals exist. Sludge mixed
directly with plant residue did not have an
inhibiting effect on the mineralization of
organic C.
Physical and Chemical
Changes in Sewage-Sludge-
Amended Soil and Factors
Affecting the Extractability of
Selected Chemical Elements
Objectives of the study reported here
were as follows: (1) Determine changes
in chemical and physical properties of a
soil that had been annually irrigated with
anaerobically digested municipal sewage
sludge during six successive growing
seasons; (2) investigate changes in 0.1 N
HCI and 2.5% CH3COOH extractable
quantities of P, Fe, Mn, Zn, Cu, Ni, Cr, Cd
and Pb from control and sludge-amended
soils; and (3) employing the same two
acids, examine changes in extractable
levels of the previously listed elements in
soil samples adjusted to different moisture
contents and incubated at different soil
temperatures.
On maximum-sludge-treated plots,
accumulated solids (dry weight equiva-
lent) incrementally applied during the 6
years amounted to 369 metric tons/ha in
1974.
The incorporation of 369 metric tons/ha
of dry solid residuals of liquid sludge
suspensions applied by furrow irrigation
on Blount silt loam in more or less equal
increments over a period of 6 years
caused significant increases in several
plant nutrient and non-nutrient elements.
Soil contents of organic C and total N
were increased more than twofold. The C
to N ratios were 11.5 and 11.7, respec-
tively, for control and sludge-amended
plots; thus, they were not significantly
different. Sludge applications caused a
4.4-fold increase in total P. Except for Fe
and Mn, soil contents of all heavy metals
were significantly increased by sludge
applications. On a proportional basis, Cd
was increased to the greatest extent.
Potassium, Mg, and Na contents were
about the same in control and sludge-
amended soils. Liming of soils probably
was the major cause of differences in Ca
levels.
The pH was not significantly different for
control and sludge-amended soils. Rela-
tively high annual applications of digested
sludge caused a significant increase of
2.5 meq/100 g in soil cation exchange
capacity. Exchangeable concentrations of
several heavy metals were higher in
sludge-amended soils, but total exchange-
able concentrations as a percent of cation
exchange capacity were not significantly
different. Digested sludge applications
increased the total water-holding capacity
(moisture content at 1 /3 atmospheres air
pressure) of the soil, but available water
holding capacity (moisture content at 1 /3
atmosphere less content at 15 atmos-
pheres) was unchanged.
Animal Studies
Selected Chemical Elements in
Tissues of Pheasants Fed Corn
Grain Produced on Sewage-
Sludge-Amended Soil
The feeding of corn (Zea mays L) grain
produced by the use of sewage sludge as
a fertilizer was initiated in the winter of
1973 using pheasants (Phasianus colchi-
cus) as test animals. Total sludge applied
during the 6 years (1968 through 1973)
on each maximum-treated plot amounted
to 369 metric tons/ha (dry weight).
Sludge application significantly in-
creased concentrations of Zn, Cd, Ni, K,
and Pin corn. But only Cd was significant-
ly increased in birds, and only in duo-
denal, liver, and kidney tissue when the
grain was fed to pheasants. Cd was not
increased in muscle tissue. Concentra-
tions did not exceed the range that is
normal for wild pheasants. No correlation
was shown between chemical composi-
tion of the grain and weight changes of
the birds, or in the amount of grain they
consumed.
Effects of Sewage-Sludge-
Fertilized Corn on Growing
Swine
In 1974, corn grain was harvested from
the control and sludge-amended plots of
the long-term, continuous corn study that
was initiated in 1968. Corn harvested
from these plots after 6 years of sludge
treatment was ground and incorporated
as 79.4% of a standard swine ration
formulated for 16% protein.
Measurements of potential manifesta-
tions of toxicity (e.g., electroencephalo-
graphy, electrocardiography, clinical
chemistry, hematology, and histopatho-
logy) were conducted by recognized
specialists using standard techniques.
The groups on sludge-fertilized corn
generally outperformed the control
group, but the differences were not
statistically significant. Concentrations of
several chemical elements were deter-
mined in samples of liver, spleen, kidney,
muscle, brain, and bone from swine
assigned to the three feeding regimens.
Only concentrations of Cd were increased,
and only in liver and kidney tissues (P <
0.05) as a result of feeding corn grain
having elevated levels of Cd. Neither
electrocardiagrams, electroencephalo-
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grams, clinical chemistry, norhistopatho-
logical studies indicated problems from
short-term feeding of corn from fields
fertilized with sludge from a large
industrial city. Some interference with
glucose metabolism and microsomal
mixed-function oxidase activity was
indicated, but the study indicated that
short-term feeding of corn fertilized by
stabilized municipal sludge did not impair
the health or performance of swine.
Effects of Overwintering
Pregnant Swine on Soils
Heavily Amended With
Municipal Sewage Sludge
To simulate a "worst-case" study, 16
weanling purebred Berkshire gilts were
assigned to the long-term continuous
corn plots. The gilts were introduced to
the plots on November 4, 1975, and
removed on March 20, 1976. They
farrowed in October and returned to the
same plots as sows on December 2,
1976. The sows were again bred in
January while on the plots, removed from
the plots on March 15, 1977, and
farrowed in the spring of 1977. The sows
were terminated for examination after
the second litter was weaned.
No dose-related differences existed in
metal concentrations in muscle, heart, or
lung tissues. But a significant increase
occurred in Cd concentrations of the
pancreas, spleen, liver, and kidney.
Conclusions
Concentraions of NH4-N, P, K, Na, Zn,
Cu, Ni, Cd, Cr, total solids, organic-C, and
electrical conductivities of runoff and
drainage waters from sludge-treated
lysimeter plots were frequently higher
than those of similar samples from
control plots. Concentrations of NOa-N
were markedly increased in drainage
water and, to a smaller extent, in runoff
water. Soil concentrations of several
chemical elements also increased, but P-
toxicity in soybeans was the only phyto-
toxic condition produced by excessive
sludge loading rates applied each year.
Effects of P-toxicity were evident only
during the first year after sludge applica-
tions were terminated. Metal concentra-
tions in corn and soybean tissues, and
especially in corn grain, decreased
rapidly following the termination of
sludge applications. Uptake of metals by
corn grown on three soil types with very
different cation exchange capacities was
about the same from plots that had
received similar sludge treatments.
Testing of inbred cornlines and their
progeny demonstrated that the capacity
to exclude Cd from the aerial parts of
plants is an inherited characteristic. This
result suggests that metal uptake could
be controlled through plant breeding.
Analyses of dry-milled corn grain and
wheat showed that major portions of Cd
and other inorganic elements were
contained in those fractions used as
animal feedstuffs.
Applying sludge each year for 10 years
on continuous corn plots improved soil
physical properties and never adversely
affected seed germination. Organic
matter in sludge is mineralized within a
few months after incorporation into soils,
and an equilibrium between ammonia
added and amounts lost each year is
approached in 3 to 4 years. Sludge
application to soil appeared to have no
deleterious effect on soil microbial
populations and enzyme activity.
When sludge is used at agronomically
appropriate rates, the risks of adverse
health effects on humans or livestock are
minimal. But when digested sludge is
used as a soil amendment at rates that
greatly exceed those needed to optimize
fertility, the possibility does exist that
trace elements may be absorbed and
transported into plant tissues in amounts
that may be harmful to animals. No
evidence was found, however, that Cd
accumulated in corn grain will result in
an animal health problem.
The full report was submitted in
fulfillment of S801356 by Metropolitan
Sanitary District of Greater Chicago
under the sponsorship of the U.S. Envi-
ronmental Protection Agency.
T. D. Hinesly andL.G. Hansen are with the University of Illinois, Urbana, IL61801.
G. Kenneth Dotson is the EPA Project Officer (see below).
The complete report, entitled "Effects of Using Sewage Sludge on Agricultural
and Disturbed Lands," (Order No. PB 84-117 142; Cost: $43.00, subject to
change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted et:
Municipal Environment*/ Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
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United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
* U.S. GOVERNMENT PRINTING OFFICE: 1984-759-102/887
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