vvEPA
United States
Environmental Protection
Agency
Robert S. Kerr Environmental
Research Laboratory
Ada OK 74820
Research and Development
EPA-600/S2-81-065 July 1981
Project Summary
Cropping Systems for
Treatment and Utilization of
Municipal Wastewater and
Sludge
Boyd G. Ellis, A. E. Erickson, and Lowell E. Leach
Land renovation of municipal waste-
waters is an attractive treatment
alternative to conventional sewage
treatment since the treatment achieved
is generally equal in quality to that of
conventional sewage treatment sys-
tems and is generally lower in cost. In
addition, many of the nutrients in the
wastewater applied to the land can be
removed through crop assimilation.
Additional treatment occurs as the
wastewater percolates through the
soil profile toward the groundwater.
The crops produced can be marketed
and their cash value applied toward
the capital cost, operation, and main-
tenance of the system. Corn is grown
as the major cash crop at the Muskegon
County Wastewater Treatment Facil-
ity in Michigan. Experience has shown
that corn is efficient in removing
nitrogen from applied wastewater
only during a few weeks during its
growing season. This lack of nitrogen
removal and elevated nitrogen levels
in the groundwater prompted this
study by Michigan State University to
develop more effective crop manage-
ment systems to remove nitrogen
from wastewater over a longer period
of time during the growing season. A
number of selective forages were
evaluated for their nitrogen removal
efficiency and effect on yield due to
competition with the corn. These
forages were sown in corn during
August, allowing them to become
established and provide winter cover
and also provide them an opportunity
for early emergence in the spring. The
corn was no-till planted in these forage
plots in the spring. During the planting
process, a strip of forage about 14
inches wide was killed with paraquat,
thus allowing the corn to begin grow-
ing without competition.
Corn interplanted with one of the
forages was effective in removing
nitrogen from the wastewater but in
many cases, the corn yield was reduced
because of the competition of the
forage with corn for nitrogen. Corn in
rye yielded about the same as corn
alone, but corn in ryegrass yielded
considerably less than corn alone.
Treatment of applied wastewater
also occurs as the water percolates
through the soil profile. Intense moni-
toring of the soil, soil water, and
groundwater was conducted at multi-
ple depths for a number of applied
nutrients and trace metals in all the
test plots throughout the study period.
At the beginning of the second year,
the project was expanded to include
an evaluation of wastewater spiked
with nitrogen to concentrations repre-
sentative of most wastewaters since
Muskegon wastewater is normally
low in nitrogen because it contains
industrial wastewater. Nitrogen, in
the form of liquid fertilizer, was in-
jected into the wastewater distribution
line whenever half a revolution of the
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center pivot rig was completed. Thus,
half of Circle 26 received nitrogen-
spiked effluent and half received
wastewater of the concentration of
the normal treatment system.
In addition to nitrogen stripping
studies, sludge compatibility and
metal contaminated sludge studies
were conducted to determine the
feasibility of applying sludge to land
which is being used in a wastewater
treatment system. These sludge stud-
ies contained completely separate
objectives. One of the objectives was
to determine the loss of nitrogen by
leaching from sludge applied to land
which is being irrigated with waste-
water. The other objective was to
determine the compatibility of appli-
cation of metal contaminated sludge
to land being used for wastewater
treatment. This sludge was generally
high in Copper (Cu), Iron (Fe), Nickel
(Ni), Chromium (Cr), and Zinc (Zn);
above average in Cadmium (Cd) and
Lead (Pb); and about average in Man-
ganese (Mg).
Yield of corn was increased an
average of about 20 hectoliters per
hectare (23 bushels/acre) for the
range of sludge loadings. It was deter-
mined that there was little advantage
in applying greater than 11 tons per
hectare (T/ha) of sludge as far as yield
was concerned. Although some yield
increase was obtained with addition of
22 T/ha, economically the returns
would favor the lower application
rates over larger acreage.
The only heavy metal to be increased
significantly in the grain wasZn. Three
heavy metals, Zn, Cu, and Ni were
shown to leach in the soil and to give
increased levels in the groundwater
under the highest sludge application
rate. Low rates of sludge application
(i.e. less than 54 T/ha) did not appear
to be a hazard to either the crop or to
groundwater contamination by leach-
ing through these sandy soils.
The full project report (see next
paragraph), describes the experiments
and results in detail and recommends
management practices for nitrogen
control at the Muskegon Wastewater
Treatment Facility.
This Project Summary was devel-
oped by EPA's Robert S. Kerr Environ-
mental Research Laboratory, Ada,
OK, to announce key findings of the
research project that is fully documen-
ted in a separate report of the same
title (see Project Report ordering
information at back).
Introduction
Wastewater renovation by application
to land has been practiced in many
small communities throughout the
United States at increasing numbers of
locations for the past fifty to sixty years.
Most of the systems have either been
operated as high-rate infiltration sys-
tems for disposal, or as irrigation sys-
tems in water-deficient regions for
increased crop yield through use of both
water and nutrients. Little regard in
either operation was given to the actual
land treatment capability until recent
years. Investigation of systems in opera-
tion illustrated clearly that a high degree
of wastewater treatment actually does
occur as the water percolates through
soils combined with various plants
utilizing available nutrients. The applied
nutrients in the wastewater can be
utilized in the production of cash crops,
thereby providing a portion of the funds
for operation and maintenance of total
treatment systems.
These facts prompted the construction
of the largest municipal wastewater
land treatment system in the United
States. The system, located in Muske-
gon County, Michigan, collects munici-
pal sewage from the entire county,
aerates it, and places it in large storage
Fagoons where it is used to irrigate over
5,000 acres of corn and a few other
crops during the months of May through
October each year.
Corn, however, the high value cash
crop grown on the farm has been found
to actually be effective in removing
nitrogen from the applied wastewater
only for a short period of time during the
corn's growing season. Therefore, sig-
nificant amounts of nitrogen are leached
through the soil profile as wastewater is
applied during the rest of the irrigation
season. Lack of adequate nitrogen
removal prompted this study by Michigan
State University as detailed in the
following discussion.
Technical Approach
Michigan State University's three-
year study of nitrogen management of
applied municipal wastewater through
special cropping practices was conduct-
ed at Circle 26 of the Muskegon Waste-
water Treatment Facility for the growing
seasons of 1976, 1977, and 1978
(Figure 1). The prime objective of this
study was to develop more effective
crop management practices to remove
nitrogen from the municipal wastewater
used to irrigate crops for the total
irrigation season. The soils at this sit
are sandy and quickly react to loading <
wastewaters and sludge. During th
course of this study, evaluations wer
made of nitrogen uptake and reduce
corn yield when forage crops such a
rye, ryegrass, and oats were intercrop
ped with corn. These studies include
evaluation of the soil nitrogen statu
and nitrate movement to groundwatei
A crop management system in whic
corn is no-till planted into fall establishe
oats, rye, or ryegrass cover crop wa
developed. This technique require
spraying a strip of forage about 1
inches wide with a herbicide (paraqua
to kill the strip of forage so the plante
corn could become established wit
little competition. The remaining forag
could then remove nitrogen until bot
the forage and corn competed for th
available nitrogen.
Rye is a winter grain which is plante
in the late summer and is used as
forage for livestockduring winter month;
It germinates and grows in the fall and i
dormant or slow growing in the winte
In the spring the rye grows rapidly an
matures in early summer. Its period (
maturing and reseeding is the sam
period in which corn is growing mo;
rapidly and adsorbing nutrients at th
greatest rate. Since the two crop
generally do not accelerate in growth £
the same time, corn and rye shoul
compliment each other almost perfect!'
Other forage selectivity studies wer
also performed to determine their pc
tential for nitrogen stripping whe
intercropped with corn. These forage
included red clover, alfalfa, birdsfoc
trefoil, tall fescue, orchard grass, quact
grass, and reed canary grass. The fir;
three of those forages, when intercrop
ped with corn, resulted in effectiv
nitrogen removal without appreciabl
reduction in corn yield due to forag
competition. However, yield of corn wa
drastically reduced when tall fescue c
orchard grass was the forage of choic
because the herbicide used with the nc
till planter failed to give a satisfactor
stand. Quackgrass and reed canar
grasses were intermediate in their yiel
reducing efficiency.
At the beginning of the second yej
(1977), the project was expanded t
include an evaluation of wastewate
with a higher nitrogen content whic
would be representative of most waste
waters since Muskegon wastewater
lower than normal in nitrogen. Nitroge
was injected in the form of liquid fertil
zer, into the wastewater distributio
-------
line whenever the center pivot irrigation
rig completed a half revolution. Thus,
half of Circle 26 received nitrogen
spiked effluent, and half received normal
wastewater. The nitrogen injection for
the high-nitrogen studies boosted the
average total nitrogen from 16 to about
25 parts per million, which was less
than anticipated. Apparently, a portion
of the nitrogen in the spiked wastewater
was lost by volatilization during spraying.
Corn yield, nitrogen stripping with inter-
cropped forages, and nitrogen leaching
were compared for both levels of nitro-
gen concentrations on separate halves
of the study area. All the evaluations
performed on the normal wastewater
study plots were also performed on the
nitrogen spiked half of the study area.
In addition to the low and high nitrogen
stripping studies utilizing forage crops
for wastewater treatment, two studies
were conducted to evaluate the applica-
tion of sewage sludge to agricultural
land. One of these studies was designed
to evaluate the compatibility of applying
sludge to lands used for wastewater
treatment. The evaluation was conducted
on plots on which only corn was grown
during the last two years of the study.
This sludge study was initiated in 1977
at the beginning of the nitrogen-spiked
wastewater studies previously described,
and continued through the 1978 grow-
ing season. The major goal of the study
was to determine the added effect of
sludge application on corn yield, com-
pared to the selected corn and forage
nitrogen-stripping studies. This study
also includes a comparison of the fate of
nitrogen added to the ecosystem by the
sludge and applied wastewater at two
in Tiie $22 = 22T/HA Sludge
~~ — — — R = Replicate
High Nitrogen
Wastewater
Drain Tile
'C-
Center^ Pivot
Drain Tile
Normal
Wastewater
Drain Tile
RG
CR
Rz
CR
R^
RG
R2
C
CRG
CRG
R^
C
Sludge Rates
CR
RG
RA
/
CRG
R3
C
R3
RG
R3
CR
R3
C
RA
Forage Adaptation
CRG
RA
Drain Tile
figure 1. Plot arrangement for low and high nitrogen N-stripping experiments.
different nitrogen concentrations. Prior
to crop planting each spring, a selected
number of high nitrogen tests plots
were loaded with sludge at two rates, 7
and 22 T/ha. The changes in the soil,
plant tissue, and groundwater were
monitored through time and compared
with data from plots where both low and
high nitrogen wastewater was applied.
The objective of a second sludge
study, conducted on separate isolated
plots, was to evaluate the effect of
applying a heavy-metal contaminated
sludge to plots where corn is grown and
irrigated with municipal wastewater.
This particular sludge was highly con-
taminated with metals from the Grand
Rapids, Michigan industries and con-
tained high concentrations copper
(Cu), nickel (Mi), cadmiun (Cd), zinc (Zn),
lead (Pb), and chromium (Cr). Specific
plots were set aside and loaded with this
sludge at the rates of 11, 22, 54, and 99
tons per hectare during the first year.
The plots were subdivided each suc-
ceeding year and retreated with sludge
each spring. Therefore, plots receiving
the highest metal additions exceeded
the suggested maximum by 2 - 3 times
for Cd, 13 - 14 times for Ni, 6 - 7 times
for Cu, and 12-13 times for Zn.
A number of parameters were mea-
sured to determine the impact metal-
contaminated sludge had on them.
These parameters were monitored for
the range of sludge loadings and include
grain yield, nitrogen uptake by the plant
tissue, and dry matter yields. Corn was
monitored for uptake of nitrogen (N),
phosphorus (P), potassium (K), calcium
(Ca), and magnesium (Mg) both in the
plant and in the grain through its growth
cycle. Corn was also monitored for
heavy-metal uptake in both the plant
and grain through its growth cycle.
These metals include Cu, Cd, Ni, Pb, Cr,
and Hg.
Analyses of groundwater were not
part of the original work plan of this
study; however, samples were collected
in the summer of 1978 under the highest
sludge application rate (99 + 81 +140
T/ha) and under the forage-corn treat-
ment of the nitrogen-stripping plots to
compare levels of heavy metals in the
groundwater. This allowed comparison
of groundwater collected beneath plots
where the maximum application of
metal-load in sludge was applied to that
of groundwater collected some distance
from the area, thereby evaluating plots
with the highest potential for leaching.
The samples were split and half of each
sample was sent to the Robert S. Kerr
-------
Environmental Research Laboratory in
Ada, Oklahoma and the other retained
at Michigan State University for analyses.
Summary of Results
Initially, the wastewater being ap-
plied to the fields was sampled at the
spray nozzles during the application of
wastewater, and by collection vessels
placed within the treatment areas.
Although the collection vessels gave
verification of uniform application rates,
the samples tended to become contam-
inated with dust and insects. Therefore,
once comparisons indicated that the
better samples were obtained from the
spray nozzles, these data were used.
While there was considerable variation
in the individual measurements, a
thorough analysis of the data did not
show a consistent variation along the
length of the irrigation system. The
amount of water applied for the whole
1976 season was 12.4 mm (0.5 in) for
each pass of the irrigation rig.
The total wastewater applied during
each season is tabulated in Table 1.
These values are much lower than the
1780 mm (70 in) per year for which the
system was designed. The poorly drained
soils, with a less than adequate tile
drain system, resulted in application of
less than the amounts designed for
Circle 26. There was no fall application
in 1976 because of the late planting and
slow drying of the corn and also the
early subfreezing temperatures which
occurred before late fall application
after harvest. The extremely wet condi-
tions in the fall of 1978 prevented
irrigation on the high nitrogen side of
Circle 26.
The considerable day-to-day variation
in the composition of the wastewater is
caused by the method of blending. The
most notable variation is during the
period of the large nitrogen demand by
corn in late June, July, and early August,
when nitrogen is injected as part of the
crop management by the county. The
average nutrient contents, specific
conductivities, and pH values of the
wastewater are presented in Table 2.
The Muskegon wastewater is low in
Table 1. Amount of Wastewater Applied Each Season
Year Season
Amount
1976
1977
1978
Summer
Summer
Fall
Summer
Fall (Low N Only)
mm
835
927
1T4
Total 1041
673
343
Total Low N 1O16
phosphorus and nitrogen due to the
large proportion of industrial waters
collected by the system. The nitrogen
injection for the high-nitrogen studies
boosts the average total nitrogen from
16 ppm to 24.4 ppm, which is less than
was planned, but there appeared to be a
loss by volatilization in spray application.
Evaluation of the effectiveness of the
various intercropping experiments for
nitrogen extraction from the soil was
based on ammonia-nitrogen and nitrate-
nitrogen removal by the plants for the
entire growing seasons for the years of
1976, 1977, and 1978. As shown in
Table 3, during 1976 the various crops
were evaluated for the normal waste-
water (Low N) used for irrigation; then in
1977 and 1978 the experiment was
expanded to evaluate the effect of
nitrogen spiked effluent (High N).
The ammonia-nitrogen (NhU-N) levels
were initially low in the soils and
remained low through the experiment
for application of wastewaters for both
low and high nitrogen. In 1976, the
values were generally in the 1 to 2 ppm
range for the surface soil and lower in
deeper horizons, indicating that the
ammonia (NH4) was rapidly being nitri-
fied to nitrate (NOs) in these well aerated
soils. Similar results were found in
1977, except that the last sample in the
fall showed an increase in NH4 in soil
layers to a depth of 30 cm, which was
attributed to the.effect of low tempera-
ture inhibiting the nitrifying organisms.
These higher values, which were still
present in the spring of 1978, also
remained higher during the growing
seasons than the two previous years as
Table 2. Summary of the Chemical Composition, Specific Conductivity and pH of the Applied Wastewater
Year and N/ level
1976 Low N
Std. Dev.
1977 Low N
Std. Dev.
1977 High N
Std. Dev.
1978 Low. N
Std. Dev.
1978 High N
Std. Dev.
Low N Avg.
High N Avg.
NO3
5.1
5.4
4.28
6.11
6.01
6.72
3.85
2.72
5.80
2.67
4.41
5.90
NH4
3.13
2.04
6.00
4.09
8.54
5.77
5.84
6.37
10.25
7.79
4.99
9.40
TKN
9.62
4.96
12.58
9.48
18.54
13.96
12.68
10.83
18.45
16.24
11.63
18.50
TN
14.48
6.05
16.86
15.20
24.55
20.05
16.53
12.54
24.25
17.24
15.96
24.40
Cl
" -ppm
240
54
280
77
271
64
181
19
182
19
233.67
226.5
PO*
2.20
0.44
2.24
0.23
2.22
0.21
1.58
0.30
1.70
0.22
2.01
1.96
TP
2.30
0.54
2.31
0.41
2.46
0.75
1.68
0.53
1.92
0.36
2.10
2.19
K
10.9
1.6
10.9
2.1
10.7
1.1
15.0
5.0
16.6
4.5
12.27
13.65
Ca
65.6
10.4
70.2
8.9
69.1
9.2
86.5
20.0
86.8
23.4
74.07
77.95
Mg
14.4
1.9
19.5
7.9
20.2
8.8
14.7
1.3
14.4
1.5
16.2
17.3
Spec.
Cond.
- fi/mohs
1070
150
980
140
980
130
1080
130
1110
130
1043
1045
pH
8.11
0.26
7.73
0.26
7.76
0.27
7.75
0.29
7.79
0.19
7.86
7.78
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3 result of the failure of the drainage
iystem on this circle. Data show there
were no significant differences between
he NH4 distributions in the soil due to
he cropping systems. The well data
'eflect values less than 1 ppm nitrogen
is NH4 during the three-year study.
The nitrate nitrogen (NO3-N) in the
soils was initially rather low in 1976,
/vhen wastewater irrigation began as
shown in Table 3. The N03-N levels
/vere even lower in the deeper soil
ayers. This is attributed to plant uptake
Df N03-N which caused the reduction of
M03-N with depth in the soil. The corn-
•yegrass treatment in 1976 was planted
is an oats-ryegrass mixture. The oats
quickly became established and reduced
he NO3 in the soil to the lowest concen-
ration of the three treatments. The soil
under the ryegrass treatment was inter-
mediate in NOa-N content because the
•yegrass developed more slowly. The
reatment of corn alone did not reduce
soil N03-N until after July, when the
;orn had developed a full canopy and
was in its stage of rapid growth. There-
ore, corn alone was the poorest treat-
ment for removing N03-N from the soil
or the entire growing season, but was
somparable to other treatments from
he 34th to the 39th week. Al I treatments
Decame less effective in reducing soil
M03-N after August.
The low N plots of 1976 were con-
inued into 1977 and 1978. During
hese irrigation seasons, nitrogen-spiked
wastewater (high N) experiments also
were evaluated for the three cropping
systems. By the spring of 1977, the rye-
jrass in the low N plots had become well
established and had the lowest N03-N
content in the surface soil. In May and
June, the corn-rye grass and corn-rye
soils had less N03-N content in the soil
than the corn-alone plots as a result of
early nitrogen uptake of the grass in the
intercropping practices. However, in
August and September, the vigorously
growing corn in the plots with corn
alone had the same or slightly lower soil
NO3-N content than the intercropped
plots. The high nitrogen plots were
established in an oats cover crop as in
previous experiments to simulate over-
wintering rye. All plots had an initial
content of about 15 ppm nitrogen as
NO3 in the surface soil. The ryegrass
grew quickly and reduced N03 in the
surface soil to about 5 ppm nitrogen in
about four weeks, while the corn-oats
system was intermediate in reducing
the soil N03 content. At the 15-30 cm
depth, the intercropped corn reduced
the NOa content of soil beginning in
June each year to below that of corn
alone. The soil-under-ryegrass plots
always had the lowest N03 content
during both years of the high nitrogen
experiments. The corn-oats system was
similar to corn alone in July but in
August as the oats matured, the corn
in both treatments did equally well in
reducing N03 in the profile.
The most significant changes, as far
as the N stripping project is concerned,
are the changes in N03-N concentration
in the leached water. In 1976, the corn-
rye treatment in which oats simulated
rye the first year, kept the N03-N in well
water lowest early in the season, re-
flecting the uptake by the quick growing
Table3.
Year
Nitrate Content of Soils-N-Stripping Experiment
Treatment
Corn
Corn-Rye
Ryegrass
Sample
LowN High N Low N High N Low N High N
1976
1976
1976
1976
1977
1977
1977
1977
1978
1978
1978
1978
Week 20
Week 20
Average
A verage
Average
A verage
Week 47
Week 47
Average
Average
Week 48
Week 48
0-1 5cm
15 -30cm
0-1 5 cm
15-30cm
0-1 5cm
15-30cm
0-1 5cm
15 -30cm
0-1 5 cm
15 -30cm
0-1 5cm
15 -30cm
1.9
1.7
3.5
2.1
4.3
3.8
2.0
0.8
3.7
1.7
3.8
1.5
7.1
3.4
2.8
1.0
4.4
2.1
10.4
3.5
ppm N
2.5
1.8
2.2
1.6
4.7
1.4
2.1
1.1
4.0
1.6
3.7
1.0
as No3
7.0
3.1
4.1
1.8
4.0
1.9
11.4
4.4
2.2
1.6
3.1
1.8
2.9
0.9
0.9
0.3
2.7
1.2
3.5
1.4
5.6
2.4
2.5
1.0
3.1
1.4
7.2
2.1
oats. These low concentrations were
continued by the N03 stripping of the
ryegrass and corn. Initially, the ryegrass
plot lost NOa-N by leaching, but as the
grass became established it was very
efficient at removing N03-N.
The corn-alone plots only stripped
NO3-N for a month which showed up in
the low N03-N well samples in August.
The average NOa-N concentration in the
well water for the first season was 3.7
ppm for the corn-ryegrass with oats, 6.2
ppm for the ryegrass alone and 8.0 ppm
for the corn alone.
In 1977, the low N experiments
showed the real benefits of the inter-
cropping systems at reducing N03-N in
the leached water after the initial
starting year since all the first-year
treatments were not complete. The
N03-N in the well water below the corn-
alone plots was rarely below 5 ppm, and
during periods when extra N was being
added to increase corn production on
the farm, the concentrations rose to
above 15 ppm indicating that corn alone
is a poor nitrogen stripper. The corn-rye
system, which was always better than
corn alone, had an average of about half
as much NOs in the well water; the corn-
rye system never allowed a concentra-
tion over 10 ppm. The ryegrass had the
lowest NOa in well water, averaging 2.1
ppm and with only one value above 5
ppm. The corn-ryegrass intercrop sys-
tem was similar to ryegrass alone;
however, this was because the ryegrass
was not sufficiently controlled to pro-
duce an acceptable corn crop. On the
high N side of the experiment, the data
indicated the intercropping plots were
not significantly different from corn
alone.
In 1977 the N stripping sludge plots
were established using sludge additions
of 7 and 22 T/ha in the area irrigated
with high N wastewater. These plots
had only corn as the crop and were thus
directly comparable to the corn-alone
stripping studies. The N03 content of
the surface layer of soil under the corn
alone plots was moderately high early in
the season. The 7 T/ha sludge applica-
tion increased the NOa content of the
surface soil slightly; this increase per-
sisted for at least three weeks before
being reduced to a value near the
control. The 22 T/ha sludge application
increased the soil NOa significantly.
The increased levels of N03 in the sur-
face soil are reflected in the 15-30 cm
layers. Both sludge applications had
higher values of NOa in the subsoil for
-------
several weeks. In fact, at the 15-30 cm
depth the soil NO3 on the 22 T/ha plots
was always higher, except during the
mid-July to mid-August period, when
the corn on these plots was growing
vigorously and reduced the N03 levels to
the level of the no-sludge corn plots. It
can be concluded that immediately after
the application of sludge, well aerated
conditions prevailed, allowing the readily
available nitrogen in the sludge to be
converted to NOs which is readily leached
unless the corn is in its rapid-growth,
maximum-demand stage, where it can
absorb the N03. Sludge, when applied at
22 T/ha, increased the concentration of
NOs-N in the well samples, but the
application of 7 T/ha sludge did not
increase the nitrate content of well
samples. Thus, applications of low
amounts of sludge is an acceptable
practice.
The yields of corn grain and silage
(Table 4) are similar to those obtained on
similar soils on the Muskegon Waste-
water Treatment Facility farm operation.
Corn and corn-rye cropping systems
produced the same corn grain and
silage yield except on the high N plots in
1977 when oats were used to simulate
overwintering rye. This intercropped
forage was too competitive for the corn.
The ryegrass intercrop significantly
reduced corn grain and silage yields
except in 1978, when there was an
overkill of the ryegrass to the extent that
nitrogen stripping was impaired. The
addition of sludge beginning in 1977
corrected the infertility of this poor soil
and gave excellent yields but did add to
the NOa leaching. The yield of corn in
1978 was suppressed compared to
1977 which may have been the result of
too much water on these soils which
have a poor underdrain system particu-
larly on the north half of circle 26. Corn-
rye has proven to be an acceptable N-
stripping winter crop without reduction
in yield; however, corn-ryegrass would
need to be better controlled to reduce
the forage competition before it could be
advocated.
The supplementary forage experi-
ments demonstrated that all of the
forages, with the exception of crown
vetch, can be grown at the Muskegon
Wastewater Facility. The crown vetch
had difficulty in germination and never
became a well-established stand. All
the others were no-till planted to corn in
1978 and their yields are presented in
the detailed manuscript. All the legumes,
rye, ryegrass, and the natural quack-
grass crops were compatible as an
Table 4. Yields of Corn and Silage on N-Stripping Experiment
Corn Grain
Corn Silage
Crop
1976 1977
1978
1976
1977
1978
Low N Corn
Low N Corn in Rye
Low N Corn in Ryegrass
High N Corn
High N Corn in Rye
7 T/ha Sludge on High N Corn
22 T/ha Sludge on High N Corn
LSD (.05)
40.6a*
42.6a
23.5b
hl/ha
68.9b
71.5b
36. 6c
72.56
42.6c
92.5a
89. lab
18.8
53.4a 26.0
54.1 a
49. Sab 6.4
35.4abc
21.7c
32.8bc
52.7 ab
18.5
T/ha
26. 3b
25. 7 b
13.7c
25. 3b
14.3c
35.7 a
34.7 a
8.2
29. 6 a
28. 5 a
25.4ab
23.4ab
14.5b
20.9 ab
20. 9 a
10.6
"Yields with the same letter are not different from others in the same column.
intercrop. Reed canary grass, tall fescue
and orchard grass would not be suitable
in these soils because their dense root
system would interfere with the no-till
corn planter. If these forages were used
they should be tested as to their N
stripping abilities.
An experiment was established to
study the influence of metal loading
rates from a metal-contaminated sludge
upon crop yield and the movement of
heavy metals under irrigation. Applica-
tion of sludge to a wastewater treatment
system such as the one at Muskegon is
considerably different from applying
sludge to agricultural lands in a conven-
tional dry land or irrigated production
system. First, the soils at Muskegon are
very sandy which will provide maximum
opportunity for sludge to be decomposed
by microorganisms because of well
aerated conditions in the soil. Secondly,
the water application rate is much
higher than in conventional agricultural
systems even where irrigation is prac-
ticed. Thus, the Muskegon Wastewater
Treatment Site allows for evaluation of
metal contaminated sludge application
to agricultural lands under conditions in
which problems are most likely to occur
due to leaching of nutrients and heavy
metals into the groundwater.
Sludge from the Grand Rapids, Michi-
gan Municipal Wastewater Treatment
Facility was transported to the test site
where it was applied by spreading
weighed quantities. A randomized block
design with five treatments (0, 11, 22,
54, and 99 T/ha) and four replications
were used. The experiment was modified
by splitting the 11, 22, and 99 T/ha
treatments in 1977 and adding yearly
sludge applications to one half of each
plot.
The concentration of all major plant
nutrients (N, P, K, Ca, and Mg) in this
sludge would be considered about
average for sewage sludges. This sludge
was high in Cu, Fe, Ni, Cr, and Zn, above
average in Cd and Pb, and average in
Mn. The quantity of metals added to the
soil by the sludge applications were
quite substantial, particularly at the
high rates. Maximum metal loadings to
agricultural soils have been suggested
by a North Central Regional Research
Committee. For soils like those in this
study, having a cation exchange capacity
of less than 5 meg/1 OOg, the maximum
lifetime metal loadings suggested in
Kg/ha were: Cd - 5.6, Ni - 56, Cu -140,
Zn - 280, and Pb - 560. The total quantity
of metals added to plots retreated with
the highest sludge rate in 1977 and
1978 was: Cd -12.6, Ni - 770, Cu - 930,
Zn - 3,490, and Pb - 370 Kg/ha. There-
fore, plots receiving the highest metal
additions (i.e. the "99 + 81+140" plots)
exceeded the suggested maximum by 2-
3 times for Cd, 13-14 times for Ni, 6-7
times for Cu, and 12-13 times for Zn.
Only about 2/3 of the suggested maxi-
mum Pb loadings was added. While the
research committee's expected lifetime
loadings for these five metals were con-
sidered to be conservative, the impact of
metal loadings at levels which are 6-19
times these suggested maximums are
largely unknown.
The effects of the above indicated
metal loadings on plant yield, plant
composition, and metal mobility and
movement in the soils were thoroughly
investigated. The effects of the range of
metal contaminated sludge loading on
corn grain yield are given in Table 5. The
yield response to the sludge application
in the initial year of study was dramatic.
Eleven T/ha of sludge increased the
yield from 64 to 102 hl/ha (73 to 117
bu/acre). Further yield increases from
additional sludge loadings were small
and statistically insignificant. Data in
Table 5 indicate a gradual decline in
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Table 5. Grain Yields from Metal Contaminated Sludge Study
Grain Yield
Treatment
1976
1977
1978
A verage
No Sludge
11
11*
22
22*
54
99
99*
LS.D.
64.4b
101.7a
107.7a
1 1 1 .9a
98.5a
18.9
- hl/l
77. 2c
81.1 be
96.8ab
93.3abc
99.9ab
92.0abc
93.2abc
100. 8 a
16.2
l,oif .
46.4c
59.4abc
70.6ab
52.0bc
73.2a
68.2ab
74.0a
67. Gab
17.6
62.7
80.7
83.7
84.3
86.6
90.7
88.6
84.2
* Annual application (11 + 11 + 11,22 + 22 + 22, and 99+ 81 + 14017 ha, respectively).
^Numbers followed by the same letter within a column are not significantly different
at the 5% level.
nutrient availability with increased
sludge loading as the nutrients were
utilized by the crop, leached, or fixed by
the soil.
The economic benefit of multiple
addition of sludge applications in suc-
cessive years was evaluated based on
the value of additional corn produced.
There appeared to be an economic
benefit from applying some sludge each
year. Although the average yield for a
single application of 11 T/ha of sludge
was 18 hl/ha (20.7 bu/acre), most of
the increase came in the first year. The
yield increase from residual sludge was
3.9 and 12.0 hl/ha in 1977 and 1978,
respectively, compared to untreated
plots but an annual application of 11
T/ha sludge gave 19.6 and 21.4 hl/ha
increase for the years of 1977 and 1978,
respectively. These facts illustrate the
economic feasibility of annual sludge
loadings. Since it is probable that sludge
would be in short supply, the question
was posed whether or not it would be
more economical to apply lowquantities
of sludge over a large acreage or apply
larger quantities to smaller acreages.
Assuming there is a uniform cost per
ton of sludge applied, calculations of the
return were made for each case. The
conclusions were that the maximum
economic benefit would be gained by
applying a small quantity of sludge to a
larger acreage.
Heavy-metal uptake in the corn plants
and grain was monitored for all three
years of the study. The Fe and Mn
content of plant tissue showed appre-
ciable decrease in uptake with years
over all treatments. The major decrease
in Fe content occurred between the first
and second sampling in 1976, while the
Mn decrease was approximately linear
each year. The authors speculate that
this reduction pattern in uptake was
probably due to an increase in soil pH
caused by the application of wastewater.
There was still adequate Fe in the plant
in 1978 for good growth but the Mn
content became lower than desirable
for optimum yield by 1978.
The Cu and Zn uptake patterns in the
plant tissue were similar. Data clearly
indicate that Cu uptake was increased
by sludge application. However, the Cu
content of plants grown on the control
plots decreased from 1976 to 1978,
probably due to the increased pH of the
soil. The same effect was observed but
was more pronounced for Zn. In 1976,
the application of sludge increased the
Zn content of plants from about 100
ppm to over 300 ppm. By 1978, the Zn
content of plants grown on the control
were about 30 ppm and those from the
highest sludge rate were down to about
100 ppm. This decrease in uptake from
1976 to 1978 could also be accounted
for by changing corn hybrids during
each year since hybrids are known to
absorb varying quantities of Zn when
grown in the same environment.
Zinc was the only heavy metal of
those monitored whose content was
increased in both the tissue and the
grain by sludge application. A nearly
linear increase in Zn content of both
tissue and grain occurred in 1978. The
Zn content of the grain was nearly
doubled by the highest sludge applica-
tion (3,490 Kg Zn/ha). However, thisZn
level in the grain would not be considered
toxic to either animals or humans. The
Zn content of plant tissue from the
sludge treated plots in the initial year
were very high but not high enough to
be toxic to either plants or animals.
Although there was an increase in Zn
content in the corn grain, the increase
was relatively small compared to the
increase in the plant tissue. The in-
corporation of cadmium (Cd) into the
food chain through the use of sludge on
agricultural land is of major concern.
The sludge used in this study had a
moderate Cd concentration and 12.6
Kg/ha of Cd were applied to the high
sludge loaded plots over a three year
period. The Zn application from this
sludge was more than 100 times the Cd
rate. Nevertheless, some apparent in-
crease in Cd occurred in the young
tissue in 1976 but was near the detec-
tion limit. No Cd was detected in plant
tissue in 1977 and 1978 and no Cd was
detected in the grain in any year.
The data indicated that sludge appli-
cation did not significantly affect the Pb,
Ni, Cr, or Hg content of the plant tissue
or grain, although an evaluation is
difficult since metal concentrations
were usually at or below detection
limits.
Both DTPA extractable and total heavy
metals were followed in the soils
throughout the three years of the ex-
periment. Soil analysis for the surface
soil (0-15 cm) showed a linear increase
in DTPA extractable Zn with Zn applied
in the sludge in 1976. About one-sixth
of the Zn applied in the sludge was
extracted by the DTPA at the end of the
season. The next soil layer (15-30 cm)
showed an elevated Zn content at the
highest Zn application rate but no
increase at the lower loading rates. The
extractable Zn in the surface layer de-
creased considerably by the end of 1977
but did not change appreciably in 1978.
Analyses indicate that a portion of the
Zn migrated into the groundwater while
the major portion of that applied over
the three year study precipitated in the
soil as pH increased with additional
sludge and wastewater.
DTPA extractable Cu and Ni both
increased linearly in the surface layer
with application rate similar to Zn. Even
though Cu was more variable than Zn
the trends were similar. About 10 per-
cent of the added Cu was DTPA extract-
able. As with Zn, theCu level inthesub-
soil was increased by the highest appli-
cation of sludge during the first year.
However, Cu did not become less soluble
with time as did Zn. This is understand-
able since it is known that Cu will
remain available for many years in soils
-------
once it has been applied and is not so
dependent on soil pH as are other heavy
metals. The Ni level in the soil decreased
with time particularly at high levels of
applied Ni. Data indicated that Ni was
leached into the soil profile in a manner
similar to Zn. The DTPA extractable
levels of other heavy metals were not
increased by the addition of sludge
which would suggest that they should
not be susceptible to leaching or in-
creased plant uptake.
Groundwater samples were collected
in the summer of 1978 under the highest
sludge application plots (99 + 81 +140
T/ha) and under the forage-corn treat-
ment of the N stripping plots where no
sludge had been applied. Sampling from
these separate'areas provided a com-
parison of the levels of heavy metals in
the groundwater under the maximum
application of sludge to a treatment that
was removed from the area assuring
that no contamination existed.
Data clearly indicated that Zn, Cu, and
Ni all had leached into the groundwater
under the highest sludge loaded plots.
Zinc values were approaching one ppm
and exceeded this value for one month
at the end of summer. The level of Zn
applied to the plots where groundwater
samples were collected was 3,490
Kg/ha, which is clearly an exorbitant
quantity of Zn to apply under any cir-
cumstance. The results would indicate
that an undesirable quantity of Zn
reaches the groundwater under such
high loading rates.
The Cu increase in the groundwater
beneath the high sludge loaded plots
was about double that of the control
area. Thus, movement was confirmed
which agrees with the DTPA extractable
soilCu and Zn values but the quantity of
Cu is not excessive even under the high
quantity of Cu addition (930 Kg/ha).
Like Cu and Zn, Ni content of the
groundwater also increased under
sludge application. The quantity of
increase appeared to be intermediate
between Cu and Zn and again indicated
that movement was occurring. No de-
tectable Hg was found in the ground-
water at any time. Increases of Cr, Cd,
and Pb may have occurred but the great
variation between replicate samples
made this uncertain since surface
contamination is possible.
Conclusions
As a result of this research effort, a
number of conclusions can be drawn
concerning the fate of nutrients and
8
heavy metals applied to sandy soils at
municipal wastewater land treatment
sites which are used to grow corn as a
major cash crop.
In the nitrogen stripping studies, the
nitrogen added in the wastewater was
rapidly converted to nitrate nitrogen
(N03) leaving very low levels of ammonia
nitrogen (NH«) in the soil during two of
the three years of study. Even during
periods when rainfall combined with
wastewater resulted in poor soil aeration,
levels of NH4 rarely exceed 4 ppm in the
soil profile.
Corn grown alone was only effective
in removing nitrogen during a four-
week period during its rapid growth
near maturity beginning in late July. At
other times the N03 levels moving
through the soil were near those of the
applied water.
Ryegrass forage was the best treat-
ment for removing nitrogen from the
wastewater for the entire season. How-
ever, during the four week period dis-
cussed above there was little difference
in cropping systems with respect to the
quantity of nitrogen removed.
Intercropping forage with corn reduced
the total nitrogen leached considerably
when compared to corn alone. The
Muskegon system was generally nitro-
gen deficient leaving a delicate balance
where the corn yields were reduced by
as much as 50 percent if the forage was
too vigorous. When forage was con-
trolled with paraquat the intercropped
corn yielded about the same as corn
alone.
A management system where rye is
strip killed with paraquat and then no-
till corn planted will produce a satis-
factory management system to effec-
tively strip nitrogen from the water and
produce a satisfactory corn yield. The
varieties of rye used in this study did not
shatter in the field to reseed themselves
in late summer. A search for varieties of
rye which would shatter when matured
could preclude seeding the rye each
year.
A study to compare different forages
showed that corn intercropped with red
clover, alfalfa, birdsfoot trefoil, and
ryegrass gave satisfactory yields. Yields
were drastically reduced when tall
fescue or orchard grass was the forage.
Rye, quackgrass, and reed canary grass
were intermediate in affecting yield.
When sludge was applied to an area
receiving about 24 ppm nitrogen in the
sprayed wastewater, a sludge loading
rate of 7 metric tons per hectare (T/ha)
gave little increase in NOs in the soil.
However, when sludge was applied at
22 T/ha under the same conditions,
N03 increased in both the surface and
the 15-30 cm layer of soil.
The application of sludge at about 11
T/ha increased the corn yield from 64 to
102 hectoliters per hectare (73 to 117
bu/acre). Rates of sudge application
above 11 T/ha did not show an appre-
ciable increase in yield over the 11 T/ha
rate. Economically, the returns would
favor application of a 11 T/ha rate over a
large acreage rather than heavy appli-
cations of sludge to small acreages.
Zinc (Zn) was the only metal to be
significantly increased in the corn grain
by the additions of sludge. Although the
level was increased from about 30 to 50
ppm Zn in the grain, this level is quite
safe in a food grain. Zinc, Copper (Cu),
and Nickel (Ni) were found to move in
the soil and to give increased levels in
the groundwater under the highest
sludge application rate (3,490, 930, and
770 Kg/ha) of Zn, Cu, and Ni, respec-
tively. Zinc content of the groundwater
was increased from about 0.1 ppm to
about 0.8 ppm, Cu from 0.04 to 0.13
ppm and Ni from 0.03 to0.07 ppm under
the heaviest sludge application as com-
pared to no sludge. Low rates of sludge
(less than 54 T/ha) did not appear to be
a hazard to either crop or leaching on
these sandy soils.
Recommendations
Effective treatment of wastewater by
land application must include careful
management of the land and crop
resources to obtain maximum nutrient
removal through high production and
simultaneously produce desireable
groundwater. Because of the inability of
corn to reduce NO3 in the soil solution
during much of the growing season it
cannot be recommended as the crop
except for a system with very low
incoming N levels (i.e. less than 10 ppm
N m the water being applied to the land).
Land treatment systems receiving
wastewater containing high quantities
of N should consider forages or forages
intercropped with corn to renovate the
wastewater. A management system is
suggested where rye is intercropped
with corn by killing a strip of the rye with
a su itable herbicide at the ti me that corn
is no-till planted. This reduces the
competition for nutrients in the corn
until it reaches a height sufficient that it
will shade the rye and thus reduce the
competition. A rye that shatters easily
could eliminate the need to reseed the
rye each summer; however, the varieties
-------
that were used in this study resisted
shattering.
Application of sludge is compatible
with wastewater treatment systems but
the application rate should be kept low.
At application rates less than 54 T/ha,
movement of heavy metals in the soil
profile did not appear to be a problem.
Uptake and translocation of heavy
metals into the grain were only noted in
the case of Zn. The recommendation for
a low application of sludge will give the
greatest economic returns per ton of
available sludge and at the same time
lessen the chance of leaching of metals
from the sludge.
BoydG. Ellis and A. E. Erickson are with the Department of Crop and Soil Science,
Michigan State University. East Lansing, Ml 48824.
Lowell E. Leach is the EPA Project Officer (see below).
The complete report, entitled "Cropping Systems for Treatment and Utilization
of Municipal Wastewater Sludge," (Order No. PB 81-187 254; Cost: $ 17.00.
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 at:
Robert S. Kerr Environmental Research Laboratory
U.S. Environmental Protection Agency
P.O. Box 1198
Ada, OK 74820
, US GOVERNMENT PRINTING OFFICE 1981-757-012/7200
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