EPA-600/2-77-014
April 1977
Environmental Protection Technology Series
>
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into five series. These five broad
categories were established to facilitate further development and application of
environmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ENVIRONMENTAL PROTECTION
TECHNOLOGY series. This series describes research performed to develop and
demonstrate instrumentation, equipment, and methodology to repair or prevent
environmental degradation from point and non-point sources of pollution. This
work provides the new or improved technology required for the control and
treatment of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-77-014
April 1977
EFFECT OF LAND DISPOSAL APPLICATIONS OF MUNICIPAL WASTES
ON CROP YIELDS AND HEAVY METAL UPTAKE
By
P. M. Giordano and D. A. Mays
National Fertilizer Development Center
Tennessee Valley Authority
Muscle Shoals, Alabama 35660
Interagency Agreement No. EPA-IAG-D4-0415
Project Officer
Carlton C. Wiles
Solid and Hazardous Waste Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
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DISCLAIMER
This report has been reviewed by the Municipal Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for
publication. Approval does not signify that the contents necessarily
reflect the views and policies of the U.S. Environmental Protection
Agency, nor does mention of trade names or commercial products consti-
tute endorsement or recommendation for use.
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FOREWORD
The Environmental Protection Agency was created because of increasing
public and government concern about the dangers of pollution to the
health and welfare of the American people. Noxious air, foul water,
and spoiled land are tragic testimony to the deterioration of our
natural environment. The complexity of that environment and the inter-
play between its components require a concentrated and integrated attack
on the problem.
Research and development is that necessary first step in problem solu-
tion and it involves defining the problem, measuring its impact, and
searching for solutions. The Municipal Environmental Research Labora-
tory develops new and improved technology and systems for the prevention,
treatment, and management of wastewater and solid and hazardous waste
pollutant discharges from municipal and community sources, for the pre-
servation and treatment of public drinking water supplies, and to mini-
mize the adverse economic, social, health, and aesthetic effects of
pollution. This publication is one of the products of that research; a
most vital communications link between the researcher and the user
community.
In the late 1960's, predecessors of the Environmental Protection Agency
initiated projects to investigate and demonstrate the use of composting
as a methodology for managing municipal solid waste in the United States.
For composting to be successful in the United States, markets would have
to be established for the compost products, or at least acceptable dis-
posal techniques for the compost product would be required. A logical
choice was the application of composted waste materials to crop lands as
an organic soil supplement,to other lands for reclamation and/or to
lands merely as a disposal site.
During 1969, field and greenhouse experiments were begun to investigate
the effects, on selected soils and plants, of composted waste materials
when applied to the lands. Because such studies require long periods to
determine effects, they were continued after the termination of the
Johnson City Composting project. This report provides the cumulative
results of the field and greenhouse research conducted from 1969 through
1975. It provides basic data on the effects of organic waste materials
when applied to selected soils and crops and will add to the knowledge
required to determine the environmental consequences of using the land
as a receptor of waste materials.
Francis T. Mayo, Director
Municipal Environmental Research
Laboratory
TM
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ABSTRACT
This report presents the cumulative data acquired from 1969 through
1975 from field and greenhouse investigations pertaining to applica-
tion of municipal compost and sewage sludge on cropland. Multiple
applications of composted garbage refuse totaling 900 metric tons per
hectare have resulted in satisfactory crop growth with only a moderate
increase of some heavy metals in plant tissue. In contrast lower
rates of several domestic sewages resulted in significant uptake of
certain metals, especially in more sensitive species, such as leafy
vegetables and string beans. Plant availability of metals derived
from sewage seems to be related to product matrix rather than to
total metal content. Very little downward movement of heavy metals
was observed under conditions of heavy leaching in the greenhouse or
natural rainfall outdoors. These results suggest that ground water
contamination from heavy municipal waste application is unlikely
except in very acid soils where mobility would be greater.
This report was submitted in fulfillment of Contract No. EPA-IAG-D4-0415
by the Soils and Fertilizer Research Branch of the Tennessee Valley
Authority under the partial sponsorship of the Environmental Protection
Agency. Work was completed as of December 1975.
IV
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CONTENTS
Page
Abstract iv
List of Figures vii
List of Tables viii
Section I Summary 1
Section II Conclusions 3
Section III Recommendations 4
Section IV Introduction 5
Section V Field Studies 6
A. Response of Forage Sorghum and Common
Bermudagrass to Municipal Waste Compost 6
B. Response of Sweet Corn and String Beans
to Zinc and Other Heavy Metals Contained
in Municipal Wastes 17
C. Heavy Metal Content of Several Vegetable
Species Grown in Soil Amended with
Sewage Sludge 36
D. Influence of Soil Heating on Plant
Availability of Heavy Metals Applied
in Municipal Sewage Sludge 44
Section VI Greenhouse Pot Studies 48
A. Plant Uptake of Heavy Metals from
Sewage Sludge As Affected by Soil pH 48
B. Response of Corn to Zn and Cr in
Municipal Wastes Applied to Soil 50
C. Relationship of Zn and Cd Supply
to Uptake by Fescue 56
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CONTENTS
(Continued)
Page
Section VII Soil Mobility Studies 60
A. Nitrogen Effects on Mobility and
Plant Uptake of Heavy Metals in
Sewage Sludge Applied to Soil Columns 60
B. Movement of Heavy Metals in Soils from
Municipal Wastes and Inorganic Sources 67
Section VIII References 69
Section IX Publications 71
Section X Appendix 72
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TABLES
No. Page
1 Chemical Analyses of Composts Used (%, Dry-Weight
Basis) 7
2 Nitrogen Contribution from Compost 12
3 Compost Effects on Nutrient Concentrations in
Sorghum Forage 13
4 Compost Effects on Some Chemical Characteristics
of Soil 14
5 Compost Effects on Some Physical Characteristics
of Soil 14
6 Common Bermudagrass Yield, As Affected by Compost
and N 16
7 Concentrations of Several Heavy Metals in Sango
Silt Loam Extracted by 0.5 N HC1 (1972) 19
8 Dry Forage Yields and Concentrations of Several
Heavy Metals in Corn Forage and Grain (1972) 20
9 Dry Yields and Concentrations of Several Heavy
Metals in Bean Vines and Pods (1972) 22
10 Concentrations of Several Heavy Metals in Sango
Silt Loam Extracted by 0.5 N HC1 (1973) 24
11 Dry Forage Yields and Concentrations of Several
Heavy Metals in Corn Forage and Grain (1973) 25
12 Dry Yields and Concentrations of Several Heavy
Metals in Bean Vines and Pods (1973) 27
13 Concentrations of Several Heavy Metals in Sango
Silt Loam Extracted by 0.5 N HC1 (1974) 28
14 Dry Forage Yields and Concentrations of Several
Heavy Metals in Corn Forage and Grain (1974) 29
15 Dry Yields and Concentrations of Several
Heavy Metals in Bean Vines and Pods (1974) 31
16 Concentrations of Several Heavy Metals in Sango
Silt Loam Extracted by DTPA (1975) 32
vii
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TABLES
(Continued)
No.
17 Dry Forage Yields and Concentrations of Several
Heavy Metals in Corn Forage and Grain (1975) 33
18 Dry Yields and Concentrations of Several Heavy
Metals in Bean Vines and Pods (1975) 35
19 Heavy Metals Extracted by Water and Acids from
Tuscumbia and Decatur Sewage Sludges 37
20 Heavy Metals Extracted by Acids from Soil Amended
with Tuscumbia and Decatur Sewage Sludges (1974) .... 39
21 Heavy Metals Extracted by 0.5 !N HC1 and DTPA from
Soil Amended with Tuscumbia and Decatur Sewage
Sludges (1975) 40
22 Total Yield and Concentrations of Heavy Metals
in Vegetables, As Affected by Sludge
Treatment (1974) 41
23 Total Yield and Concentrations of Heavy Metals
in Vegetables, As Affected by Sludge
Treatment (1975) 42
24 Effect of Sewage Sludge and Soil Heating on
Vegetable Yields 45
25 Effect of Sewage Sludge and Soil Heating on
Heavy Metal Concentrations in Fruit and
Leaves of Several Vegetables 46
26 Effect of Soil Heating on Extraction of Heavy
Metals from Soils Amended with Sewage Sludge 47
27 Total Dry Matter Yield and Heavy Metal Uptake
by Mustard As Affected by Soil pH and Sewage
Sludge Application 49
28 Forage Yields and Zn and Cr Concentrations in
Three Corn Crops As Affected by Soil
Application of Municipal Wastes 51
29 Forage Yields and Zn and Cr Concentrations in
Two Corn Crops As Affected by Soil
Application of ZnSO^ and Na2Cr207 53
viii
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TABLES
(Continued)
No.
30 Soil pH and 0.5 N^ HCl-Extractable Zn and Cr after
Each of Three Corn Crops Grown on Soil Treated
with Municipal Wastes, ZnSO^, or Na2Cr207 55
31 Total Dry Matter Yield and Uptake of Zn and Cd
in Four Cuttings of Fescue 57
32 Total Dry Matter Yield and Heavy Metal Uptake in
Four Cuttings of Fescue from Soil Amended with
Sewage Sludge 58
33 Mobility of Several Heavy Metals in Columns of
Ennis Soil As Affected by N and Heavy Metal
Sources 61
34 Dry Weight and Cumulative Uptake of Several
Heavy Metals in Three Clippings of Fescue 63
35 Mobility of Several Heavy Metals in Columns of
Decatur Soil As Affected by N and Heavy Metal
Sources 65
36 Dry Weight and Cumulative Uptake of Several
Heavy Metals in Three Clippings of Fescue 66
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FIGURES
No. Page
1 Effects of Compost Application on Forage
Sorghum Yield
2 Residual Effects of Compost Application
on Forage Sorghum Yield 10
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SECTION I
SUMMARY
Much attention is being directed toward land application as a means
of municipal waste disposal. However, before this practice can be
recommended more research is necessary with regard to waste char-
acterization, pathogenicity, site selection, and long-term effects on
crop production and food chain pollution. The present investigation
was undertaken with the principal objective to study heavy metal
implications in soils and plants. Due to the limited resources
directed to this project, investigation of other factors was not
feasible.
Since many sewage sludges contain appreciable quantities of zinc (Zn)
as well as potentially toxic heavy metals, including cadmium (Cd),
nickel (Ni), and lead (Pb), recent investigations have been initiated
to study the reactions of these metals in soils and factors which
affect their uptake by crop plants.
Field studies were begun in 1968 to evaluate composted municipal
waste as a soil amendment (Section V.A.). Yield responses were
observed with annual compost applications of rates up to 143 and 80
metric tons/hectare (ha) on sorghum and bermudagrass, respectively.
However, the highest yields of either crop attained with compost were
surpassed by application of fertilizer nitrogen (N) at the rate of
180 kg/ha, together with adequate phosphorus (P) and potassium (K).
Aside from enhancing the fertility of the soil, compost applications
increased moisture-holding capacity and decreased the bulk density
and compression strength of the soil. These effects, however, did
not persist beyond 3 years. Although these experiments indicated
that large tonnages of compost can be applied to grass- or cropland,
the economic return is minimal. Of further concern was the observa-
tion that compost-treated crops showed elevated levels of Zn and to a
lesser extent other heavy metals, although these were largely derived
from the sewage sludge added to the composted garbage.
The next phase of this investigation was to compare the immediate and
residual availability of Zn to vegetable crops when applied in the
form of ZnSOi+ or as a constituent of municipal garbage compost or
sewage sludge (Section V.B.). When ZnSO^ and compost or sewage
sludge were applied at rates resulting in comparable applications of
Zn, availability of Zn to both sweet corn and string beans was consid-
erably greater from ZnS04 over a 4-year period. In general string
beans were less tolerant of high Zn treatments even when applied as
sewage sludge. Of the other heavy metals routinely monitored in these
crops, only Cd levels exceeded check values in the plant leaves;
edible plant parts were relatively unaffected. Bean pods only appeared
to accumulate Ni from sewage sludge, reaching levels two to four
times those from nontreated plots. Although there was no indication
1
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that the elevated Cd or Ni levels were phytotoxic, the consequence of
animal or human consumption was not determined.
Other vegetable species were grown on soil amended with anaerobically
digested sewage sludge obtained from two municipalities in north
Alabama (Section V.C.). Increased yields of tomatoes and squash were
obtained in response to application of both waste materials; other
species were unaffected. Leafy vegetables, such as lettuce and
spinach, were accumulators of Zn, Cd, and copper (Cu). Radish and
turnip roots contained somewhat lower levels of Zn and Cd, while
vegetables consumed as fruits or seed pods were relatively low in
heavy metal content. Despite the differences in metal content between
the two sewages, plant uptake was not always related to content in
the material. This suggests that the chemical form may also be
important in evaluating sludges for use on agricultural land.
Pot experiments conducted in the greenhouse to study phytotoxic
levels of chromium (Cr), Cd, and Zn indicated that inorganic forms of
these metals are taken up by plants in greater quantities than from
organic wastes (Section VI). Whereas Zn concentrations in corn
increased with rate of Zn applied as ZnSO^ or organic waste, concen-
trations of Cr seldom exceeded check values in the plant foliage,
even though growth was depressed. Apparently, Cr is effectively
excluded by plants with very high soil concentrations, resulting in
sufficient root damage to limit growth. Cadmium was readily accumu-
lated in fescue, but growth was not depressed until concentrations
exceeded approximately 100 parts per million (ppm).
Abatement of Cu, Pb, and Ni in mustard was not accomplished by liming
the soil from pH 5.0 to 7.0. However, concentrations of Zn decreased
significantly over this range and Cd decreased slightly from pH 5.0 to
6.0. Other studies are needed to evaluate liming as a means of heavy
metal pollution abatement.
Investigations of heavy metal movement in soil profiles from munici-
pal waste applications have been conducted under simulated and
natural rainfall conditions (Section VII). Results show that mobil-
ity of heavy metals is slightly greater from inorganic than from
organic forms but is minimal even under severe leaching situations.
Based on these findings, it is unlikely that disposal rates of munici-
pal wastes applied to cropland pose a threat to our water supply.
However, the consequence of prolonged use on cropland and subsequent
soil management practices is obscure.
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SECTION II
CONCLUSIONS
1. Data herein show that large tonnages of municipal compost can be
applied on grassland or cropland with occasional positive yield
responses. However, the value is low when compared with the
cost of chemical fertilizer needed to produce equivalent yields.
Thus, composting of organic wastes should be considered largely
as a useful alternative method of disposal, rather than as a
substitute for inorganic fertilizer.
2. Application of rather high rates of sewage sludge (> 50 metric
tons/ha) may increase vegetable production of some species, but
this apparent benefit may be accompanied by increased levels of
one or more heavy metals. Since certain vegetable species are
sensitive to heavy metal accumulation, toxicity may cause
decreased yields and higher levels of heavy metals in the plants.
Although concentrations are generally higher in vegetative
tissue, in some instances the reproductive plant parts may be
sinks for certain metals. The significance of Cd and Ni concen-
trations, ranging from two to five times those in vegetation
from unamended plots, is yet to be determined with regard to
food chain implications.
3. Total heavy metal content of a sewage sludge does not necessarily
reflect plant availability. Transformations may occur in soils
which increase or decrease availability in these waste products.
The organic matter content and composition of the waste material
likely influence availability depending upon the stability of
the metal complexes formed and the subsequent resistance to
decomposition. Apparently the pH value of the sludge per se is
not a reliable indicator of plant availability. However, under
very acid soil conditions (< pH 5.0), sewage sludge high in Zn
content may be toxic to plants. Inorganic sources of Zn initially
are more toxic than organic wastes at equivalent rates of applica-
tion and constant soil pH. The consequence of multiple applica-
tions of sludge is unknown. Although heavy metals accumulate
with repeated treatment, the organic matrix seems to be protective.
4. Results show that movement of heavy metals in soil is greater
from inorganic than from complexed sources found in sewage
sludge under severe leaching conditions; other studies indicate
little difference in mobility with normal rainfall and minimal
supplemental irrigation.
5. Although moderate rates of "low risk" sludge pose little hazard
to crops, at least during the first year after application, con-
tinued use of municipal wastes may ultimately result in heavy
metal overloading, especially in some light-textured soils.
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SECTION III
RECOMMENDATIONS
1. Municipal waste materials should be carefully characterized with
respect to total elemental composition and solubility prior to
land disposal. Reactions of organic wastes in soils need
further study. Although results suggest that most heavy metals
contained in wastes are rather immobile in soils, long-term
studies must be forthcoming before the consequence of repeated
applications of heavy rates is completely understood.
2. Although a number of crop species have been identified as
excluders or accumulators of certain heavy metals, .further
delineation is necessary. Routine leaf analysis is not suffi-
cient, since certain edible plant parts other than leaves may be
sinks for particular heavy metals.
3. More greenhouse and laboratory work is needed to correlate heavy
metal uptake with soil extraction procedures. Existing extrac-
tants used for micronutrients may not be suitable for all heavy
metals.
4. There has been little evidence in these studies of heavy metal
conversion to more available forms. Organic matter content
should be monitored for several more years from plots receiving
both single and multiple applications of municipal wastes.
Furthermore, soil samples should be extracted during this period
to determine whether metal availability to plants is changing.
The effect of soil acidification and heating on solubilization
and mobilization of metals is being investigated.
5. Guidelines must be established regarding tolerable levels of
heavy metals in food chain components before the significance of
elevated levels in crops can be evaluated. It also must be
recognized that surface contamination is a contributing factor.
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SECTION IV
INTRODUCTION
Prior to about 1955, applying manures and sludges on crop and recrea-
tional land was aimed at correcting nutritional deficiencies or
adverse physical conditions rather than disposal of an overabundant
waste product. As a result, much lower rates were applied. Also,
content of potentially hazardous heavy metals was lower in manures
because it included excessive antibiotic doses of Cu and Zn (4).
Large quantities of municipal garbage and sewage sludge generated by
modern society are creating a serious problem of disposal (1). Land
filling appears to be the least costly acceptable method of disposal
in the United States. Incineration has some potential but may be
subject to many constraints. The value of municipal refuse and
sewage as sources of plant nutrients has long been recognized.
Unfavorable economics has restricted the use of these materials,
although several municipal waste products have been marketed success-
fully for many years, primarily for use on ornamentals and turf.
Rising costs of commercial fertilizers have stimulated interest in
use of sewage sludge not only for recreational areas and home grounds
but also for crop production.
Among the problems associated with land application of "disposal
rates" (> 25 metric tons/ha) of sludges for crop production are (i)
the potential toxicity to plants from contained heavy metals, (ii)
entrance of heavy metal contaminated plant material into the food
chain directly or through animals, and (iii) possible pollution of
ground waters as a result of heavy metal migration. This report
deals with the yield response and heavy metal accumulation by several
plant species grown on soil amended with varying types and rates of
municipal wastes. Special emphasis was placed on studies of cumula-
tive and residual availability of Cd, Zn, Ni, Pb, and Cu to vegetable
crops grown in the field. Also, mobility of these metals in soil was
investigated in the greenhouse and in a rhizotron-lysimeter under
leaching conditions and natural rainfall to determine whether ground
water contamination would follow heavy applications of municipal
wastes.
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SECTION V
FIELD STUDIES
A. RESPONSE OF FORAGE SORGHUM AND COMMON BERMUDAGRASS
TO MUNICIPAL WASTE COMPOST
Experiments were begun in 1969 to evaluate the effects of composted
municipal waste as a soil amendment (11, 17, 18). The primary objec-
tives were to measure crop response to applied compost and to deter-
mine the application rate above which compost might be detrimental to
crop production.
The compost was produced at Johnson City, Tennessee, in an experimen-
tal composting plant operated jointly by the Tennessee Valley Authority,
the Environmental Protection Agency (at that time, the U.S. Public
Health Service), and Johnson City (9).
The raw material was municipal waste or garbage containing food
wastes, paper and cardboard, plastic, cloth, metal, glass, and other
items found in city waste. The garbage was fortified with sewage
sludge in amounts as great as 20% on a dry-weight basis. Initially,
only coarse grinding was practiced and the compost was fluffy, poorly
composted, and contained many identifiable objects. As technology
improved, a finely ground, well composted product with a satisfactory
physical appearance was produced. Chemical analyses of the lots of
compost used are shown in Table 1.
In the first experiment at Muscle Shoals, Alabama, forage sorghum
(Sorghum bicolor L. Moench x Sorghum sudanense P. Stapf., cv.,
'Funk's 101F' and later 'Funk's 102F') was the test crop. Thirteen
treatments comparing combinations of fall and spring applications
with and without supplemental N fertilizer were compared on a Sango
silt loam soil. All high rates were applied in split fall and spring
application. Composts at total application rates ranging from 23 to
326 metric tons/ha on a dry-weight basis were applied over a 2-year
period. All plots were uniformly fertilized with 28 kg of P and 112
kg of K/ha at the beginning of the experiment. All treatments were
replicated four times in 3.7- by 9.2-meter plots.
Two cuttings of sorghum forage were removed each year from 1969
through 1971; in subsequent years the sorghum was cut only once.
Forage samples were analyzed for several macro- and micronutrients.
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In a second experiment, common bermudagrass (Cynodon dactylon L.)
was topdressed with compost In November 1968 at rates of 0, 9, 18,
and 27 metric tons/ha. In the winter of 1969-1970, compost was
applied to the same plots at triple the 1968 rate. Nitrogen rates of
0 and 180 kg/ha were superimposed on plots at each compost rate.
One-half of the N was applied in April and the other half after the
second harvest. The grass was cut four times.
1. Results on Sorghum
At the low rates where fall versus spring applications were compared,
no differences due to application schedule were noted. Yield responses
for the two cropping seasons for which compost was applied are shown
in Figure 1. Total yield levels were higher in 1969 because of more
favorable midsummer rainfall. Response was curvilinear, with the
yield still increasing at the highest application rate. It required
an application of 91 metric tons/ha of compost to produce as much
forage as 90 kg of N/ha from ammonium nitrate (NHi+N03), but none of
the compost rates produced as much forage as 180 kg of N/ha. Nitrogen
plus compost produced higher yields than either applied alone.
Compost used for the 1969 crop year was coarse and fluffy. The fall
plowdown application caused no problems but the spring application,
incorporated by disking, made the preparation of a fine, firm seedbed
impossible at application rates of 35 metric tons/ha or above. This
resulted in poor germination and uneven stands, a problem not encoun-
tered in subsequent years with finely ground compost.
While yields were lower in 1970, the response to compost was greater,
as shown by convergence of the 1969 and 1970 yield curves at increas-
ing rates. This may have been partly due to the residual effect from
compost applied for the 1969 season, but it seems likely that better
soil moisture relationships resulting from the physical effects of
high compost application were also important. As in 1969, effects
of compost and N were additive.
Sorghum was grown for 5 more years to measure residual response to the
1969 and 1970 compost applications. In 1971 the residual response
was similar to the 1969 and 1970 responses but by 1974 residual
effects had disappeared. Data for the 1971-1974 period are shown in
Figure 2. The area was fertilized uniformly each year with N and K
each at 112 kg/ha. The yield level was increased significantly by
fertilization but no residual compost response could be detected in
1974 and 1975.
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Figure 1. Effects of compost application on forage sorghum yield.
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Figure 2. Residual effects of compost application on forage sorghum yield.
10
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The contribution of compost to N in the crop is shown in Table 2.
Significant amounts of N were supplied to the crop over a 6-year
period totaling almost 400 kg/ha from the heaviest compost applica-
tion. Although it is recognized that organic N must undergo con-
version to NH^ or N03 before it is available to plants, this aspect
was not pursued. The sorghum forage was analyzed for a wide range of
elements, but aside from N, only K, sodium (Na), Zn, and Cu concen-
trations were modified by compost application (Table 3). These
increases show that the effect lasted throughout the residual harvest
period. Concentrations of Zn and Cu were still 50% higher in 1975 in
forage from high compost plots, even though the soil pH (Table 4) was
in the range where these elements are normally much less available.
This emphasizes the potential for persistence of some heavy metals in
the soil-plant system.
Table 4 shows chemical effects on soil from compost after 2 applica-
tion years and also after 3 years of residual cropping. Organic
matter content was more than doubled after 2 years of application,
but the increases were largely dissipated after only 3 residual
years, indicating that little compost was converted to stable organic
matter fractions. Soil pH was increased by more than one unit at the
highest application rate, apparently a stable effect. The pH effect
was attributed largely to the high calcium (Ca) content of the
compost.
Levels of several extractable nutrients are also shown. The added K
was presumably removed in the sorghum crops, while the additions of
Ca and magnesium (Mg) were fairly stable because of low crop uptake.
Soil Zn values were increased significantly by the compost, presum-
ably by the sewage sludge fraction. Unfortunately, Cd was not being
monitored during this phase of the investigation. Changes in soil P
could not be readily characterized because of the high level already
present in the soil.
Reductions in soil bulk density and compression strength (an indica-
tion of reduced power requirements for tillage) were significant in
1970, but there was little residual effect by 1973 (Table 5). Com-
post had a favorable effect on soil moisture holding capacity, as
indicated by the soil moisture content at the 1970 sampling. This
effect was seen during any period of prolonged moisture stress as
sorghum growing on high compost plots always showed less leaf curling.
11
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A summary of this research indicates the following:
1. Municipal waste compost can be applied at rates as high as 326
metric tons/ha over a 2-year period without any important detri-
mental effects on sorghum production or quality.
2. Yield increases were obtained with each increase in the rate of
compost application.
3. Compost appears to be worth only a few dollars per ton if equated
with the cost of enough commercial fertilizer to achieve similar
yield increases.
4. Residual yield responses were obtained for 3 years after the
last application.
5. Effects on soil organic matter and exchangeable K levels were
largely dissipated 3 years after application but changes in pH
and exchangeable Ca, Mg, and Zn persisted.
6. Bulk density and compression strength were reduced and soil
moisture content was increased by compost applications, but
these changes did not persist beyond 3 years.
2, Results on Bermudagrass
Common bermudagrass yields (Table 6) show that bermudagrass sod can
accept heavy applications of surface-applied compost and show a
slight yield response. Without added N the high compost rate pro-
duced significantly more forage than no compost in 1969, while all
compost rates were better than no compost in 1970. As with sorghum,
yield increases from compost do not pay the cost of compost produc-
tion, transportation, and application.
It seems that the most critical consideration for compost being used
on forage land is the absence of glass, metal, or other foreign
material in particles big enough to' be ingested by grazing animals or
picked up in harvested hay. However, significant quantities of heavy
metals derived from the wastes may 'also enter the food chain directly
as a result of plant surface contamination and consumed waste material.
15
-------
TABLE 6. COMMON BERMUDAGRASS YIELD, AS AFFECTED BY COMPOST AND N.
Compost rate
metric tons/ha
1969
0
0
9
9
18
18
27
27
1970
0
0
27
27
54
54
81
81
N rate, kg/ha
0
180
0
180
0
180
0
180
Dry forage yield
metric tons/ha*
1969
6.5c
11. 4a
7.4bc
11. 2a
7.6bc
12. 5a
7.8b
11. 9a
1970
2.7d
5.6b
4.0c
6. Sab
6.3c
7.2a
4.7c
13. 4a
Avg.
4.5d
8.5b
5.6c
8.7b
5.8c
9.9a
6.3c
9.2ab
*Values followed by the same letter are not significantly different
according to Duncan's Multiple Range Test (5%).
16
-------
B. RESPONSE OF SWEET CORN AND STRING BEANS TO ZINC
AND OTHER HEAVY METALS CONTAINED IN MUNICIPAL WASTES
Because of higher levels of Zn found in forage sorghum as a result of
compost application a comprehensive investigation was made of the
availability of Zn contained in garbage compost and municipal sewage
sludge relative to comparable rates of ZnSOu (7) .
This experiment was conducted at Muscle Shoals, Alabama, in the fall
of 1971 on Sango silt loam (pH 5.4). Treatments consisted of three
rates each of dry garbage compost (56, 112, and 224 metric tons/ha),
dry sewage sludge (50, 100, and 200 metric tons/ha), and ZnSOa all
incorporated into the soil to provide the equivalent of 90, 180, and
360 kg of Zn/ha. The compost was from the experimental composting
plant at Johnson City, Tennessee; sewage sludge was from the sewage
treatment plant at Tuscumbia, Alabama. Elemental composition of
these waste materials is shown in the Appendix. All treatments were
replicated four times and original plot dimensions were 3.6 by 15.0
meters (plots were subdivided in the fall of 1972 to 3.6 by 7.5
meters). Sweet corn (Zea mays L., cv. 'Silver Queen') and string
beans (Phaseolus vulgaris L., cv. 'White Half Runner') were selected
as the test crops because of their contrasting response to high
levels of available Zn. The entire area was sprinkler irrigated as
needed to assure that moisture stress would not limit plant growth.
Before planting, NHyNOa and KC1 were applied uniformly to all plots
and disked in at rates of 150 and 100 kg/ha of N and K, respectively.
Sweet corn was planted in 90-cm rows (4 rows/plot) and later thinned
to a population of 50,000 plants/ha. Corn was harvested when the
grain was in the milk stage. After the corn crop was harvested,
50 kg/ha of N as NH^N03 was disked into the soil prior to planting
string beans. String beans including vines were harvested from the
two center rows. Earlier results (J. J. Mortvedt and P. M. Giordano,
unpublished TVA data) indicated that corn was much less sensitive to
excessive Zn than field beans. Purves and Mackenzie (14) found beans
to be highly susceptible to heavy compost applications as compared
with several other garden vegetables.
Soil borings to a depth of 20 cm were taken from all plots shortly
after planting corn each year. Ten-gram samples were extracted with
50 ml of 0.5 N HC1 for 15 minutes and 20 ml of DTPA solution (10) for
2 hours at ambient room temperature, filtered, and analyzed for Zn,
Cu, Pb, and Ni by atomic absorption spectroscopy and Cd and Cr using
a flameless atomizer accessory. Sensitivity for Zn, Cd, Cr, Ni, and
Pb was 0.01, 0.005, 0.07, 0.05, and 0.06 yg/ml, respectively. Back-
ground correction was made using a deuterium continuum source in the
B channel.
17
-------
At harvest the two center rows of each plot were cut, weighed, and
both total dry matter production and yield of the edible portion were
computed. Samples of plant material were washed in distilled water,
oven-dried, ground in a Wiley mill equipped with stainless steel
knives and screens, and dry ashed at 470C for 16 hours. The ash was
digested in 5 ml of 6 II HC1 for 10 minutes and brought to 25 ml.
Solutions were then analyzed for Zn, Cu, Cd, Cr, Pb, and Ni as
described previously. Significance of yield differences due to
treatment were determined using the Duncan's Multiple Range Test.
However, because of differences in elemental concentrations arising
from growth dilution as well as treatment, statistics were misleading
in interpreting concentration data.
Weed control was not a problem during the cropping season, since a
preemergence herbicide was used. However, during late winter and
early spring a multitude of winter annual weeds covered the sludge-
and compost-treated plots. There was no evidence of inhibition of
weed or crop seed from waste treatment. In fact, seedling stands
often were superior, especially with compost, due likely to improved
physical condition of the soil.
1. Results in 1972
The early liming effect from compost and sludge application is shown
in Table 7. Soil pH increased from 4.9 in the check and ZnSOu plots
to as high as 6.3 at the highest rate of compost. About 60% of the
applied Zn was recovered from the soil with 0.5 Ni HC1 regardless of
soil pH value. Amounts of Cu, iron (Fe), manganese (Mn), and Pb
extracted from the compost- and sludge-treated plots were much higher
than from the check or ZnSOij plots; extractable Cr and Cd were
slightly higher and Ni was similar to the check.
Dry forage yields increased significantly with applications of com-
post and sludge (Table 8). No toxicity was noted with any rate of
ZnSOit- Compared with the check plots, the concentrations of Zn in
the corn forage were 2 to 3 times higher with compost and sludge and
5 to 10 times higher with ZnSOi*. This agrees with results reported
by Terman, Soileau, and Allen (18) that Zn uptake increased with
organic waste application. Concentrations of Zn in corn grain were
much lower than in forage, even with ZnSOit. Apparently most of the
Zn accumulated in vegetative tissue and was not readily translocated
to the grain. Unfortunately, it was beyond the scope of this project
to study silage content and accumulation in animals consuming the
silage.
Concentrations of Pb in forage and grain were not affected by organic
wastes. Although the sludge contained about 1,600 ppm of Pb (132
18
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kg/ha at the highest application rate), uptake was not higher when
compared with the check treatment. Lead concentrations in forage
were generally lower due to dilution from increased plant growth with
sludge and compost. As with Zn, concentrations were lower in the
grain than in the forage. It is likely that the Pb was either immo-
bile in plant roots or was unavailable due to the high soil P level.
Concentrations of Ni in both grain and forage ranged randomly among
treatments from 2.6 to 6.9 ppm. In contrast, Cd concentrations were
2 to 5 times higher with compost and sludge than with ZnSO^ or with
no treatment. Concentrations of Cd were higher in corn forage (0.7
to 5.3 ppm) than in grain (0.2 to 1.2 ppm).
Yields of bean vines increased with compost applications and the
highest rate of sludge (Table 9). As with corn there was an unex-
plained increase in yield with the 180 kg/ha rate of Zn as ZnSOt+.
However, yields dropped sharply at the 360 kg/ha rate. Pod yields
decreased with rate of ZnS04 application. Except for the highest
rate of compost, pod yields were lower than from the check plot with
all treatments. Whereas vine yields were similar with compost and
sludge treatment, yields of bean pods were reduced markedly by sludge
only. Van Loon (19) observed that bean pods tended to accumulate
mercury (Hg) to a greater extent than vines grown on sludge-treated
soil. Accordingly, bean pods may be accumulators of Zn and other
heavy metals and may be less tolerant of high levels than other plant
species.
Concentrations of Zn in vines increased from 60 ppm in the check to
499 ppm at the high ZnSO^ rate and were about 3 times higher with
sludge than with compost or the check. Levels of Zn in the bean pods
were generally lower and varied less with treatment than the vines.
Despite the relatively high Pb content of the sludge, concentrations
in both vines and pods grown with sludge were comparable to those
from the check plots. Concentrations ranged from 3.9 to 5.5 ppm in
the vines and from 0.9 to 1.8 ppm in the pods. As with corn, Ni
concentrations were variable but slightly higher in pods than in
vines. Sludge resulted in slightly higher concentrations of Ni in
both pods and vines. Levels of Cd were low in vines and pods but
were highest in vines grown with sludge.
2. Results in 1973
In the fall of 1972, all plots were subdivided with half of each plot
receiving a second application of the previous treatment. The remain-
ing half received no additional treatment so that residual effects of
the original application could be measured. Nitrogen and K were
applied as in 1972 to all plots.
21
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Concentrations of all heavy metals extracted from soil samples from
the residual half of each treated plot were equal to or slightly
lower than the corresponding values obtained in 1972 (Tables 10 and
7). Apparently some immobilization of these metals occurred with
time of reaction in the soil. Reapplication of treatments resulted
in higher levels of extractable metals but not in proportion to the
amounts applied. About half of the Zn, Cu, Pb, and Cd applied only
in 1971 was recovered with the 0.5 N^ HC1 extraction; less than one-
tenth of the Cr and Ni applied in compost and sludge was recovered.
Corn forage yields were higher in 1973 than in 1972 (Table 11)
probably due to the more favorable growing conditions. The spring of
1972 was unusually cool and wet; the spring of 1973 was warmer with
better rainfall distribution throughout the entire growing season.
Both medium and high rates of ZnSOa resulted in a significant decrease
in yield compared with the check. Yields were increased with both
the medium and high rates of compost applied once or reapplied. The
two higher rates of sludge also resulted in yield increases but only
with the single application. Differences between yields resulting
from single and repeated applications were not significant with any
treatment.
Total "marketable" ears of corn were reduced from about 12,000/ha for
the check to 5,000 at the high rate of ZnS04 with the single applica-
tion; repeated application reduced the ear count to about 1,500/ha
(data not shown). The single application of all rates of compost and
sludge resulted in ear production similar to that of the check.
Although the second application of sludge did not influence ear
count, reapplication of compost increased ear production to about
16,000/ha. Since the number of stalks per plot was relatively unaf-
fected by treatment, total ear production was a reflection of the ear
count per stalk.
Concentrations of Zn in the 1973 corn forage were higher than in 1972
even though yields also were higher (Table 11); sludge-treated plots
showed the greatest increase. The second application of ZnSO^
resulted in marked increases in Zn concentration in the forage;
increases with sludge and compost were less pronounced. In contrast,
concentrations of Zn in grain were similar in 1972 and 1973 with the
single application (repeated application in 1973 resulted in slightly
higher levels of Zn with ZnSOi+ and sludge treatments).
Concentrations of Pb in corn forage and grain were unexplainably
higher in 1973 than in 1972 irrespective of treatment. However,
differences in concentration due to treatment again were not evident.
Further, reapplication of the waste treatments did not result in
increased Pb concentration. Concentrations of Ni were lower in 1973
than in 1972 possibly as a result of dilution due to higher yields.
As with Pb neither treatment nor reapplication affected concentration
in forage or grain. Cadmium concentrations in forage and grain of
23
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the 1973 crop were comparable to those of the previous year. Levels
of Cd in forage only were slightly higher with application of compost
and sludge.
Yields of bean vines decreased progressively with each rate of
whether applied only in 1971 or repeated in 1972 (Table 12). Results
were similar with pods except that repeated application of the two
higher Zn rates was extremely toxic and growth was negligible.
Application of compost did not affect yields of either vines or pods,
but the high rate of sludge reduced pod yields significantly.
Concentrations of Zn were highest with ZnSO<+ application, interme-
diate with sludge, and only slightly higher with compost as compared
with the check. Apparently Zn derived from sludge was more available
for plant uptake than that in compost. In general Zn concentrations
in both vines and pods were comparable to those of 1972.
Levels of Pb in vines and pods were not affected by treatment or
repeated application, but concentrations in pods were much higher
than in 1972. Nickel uptake by bean pods from sludge plots appeared
to be higher than with other treatments. As in 1972, concentrations
of Cd in vines were about twice as high with sludge compared with
other treatments; concentrations were similar in pods in 1972 and
1973 and were unaffected by waste treatment.
3. Results in 1974
Residual levels of most heavy metals, especially Zn, extracted from
plots receiving treatment in 1971 continued to decrease in 1974
(Table 13). Concentrations were higher in acid extracts from soil
receiving multiple applications of municipal wastes than from plots
receiving the same total amount in a single application in 1971.
These observations suggest that some reversion of Zn and other metals
to less-soluble forms occurred. Liming of the ZnSO^ plots in 1974
resulted in a further decrease of extractable Zn.
Corn forage yields again were highest with multiple applications of
compost (Table 14). Repeated ZnSO^ applications were less toxic in
1974, probably due to the higher soil pH from liming. Accordingly,
concentrations of tissue Zn were much lower in 1974, especially where
residual effects were being measured from the 1971 application.
Levels of Cd were about the same as in 1973, being highest with
sludge application. Copper, Pb, and Ni concentrations were unaf-
fected by treatment. Zinc concentrations in corn grain were slightly
lower with ZnSO^ in 1974 and slightly higher with repeated compost
and sludge. As in forage, Cu, Pb, and Ni levels were not affected by
treatment; concentrations of Cd were higher with sludge and compost,
26
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but levels were less than 1 ppm. Total marketable ears of sweet corn
were reduced with repeated applications of ZnSOi* even though this
apparent toxicity was not reflected in depressed forage yields (data
not shown). High rates of both compost and sludge increased yields
of marketable ears.
Dry matter production of bean vines was lower in 1974 compared with
1973 (Table 15). However, as with corn, the toxic effect of ZnSOu
was diminished considerably. Concentrations of Zn were lower with
ZnSOi+j slightly higher with compost, and much higher with sludge in
1974 than in previous years. Copper and Pb contents were not affected
by treatment and levels were similar to past year's results. Levels
of Cd and Ni were three- and twofold higher, respectively, with
sludge application.
Bean yields averaged about half of the 1973 production (Table 15).
In contrast to corn, bean yields did not increase with municipal
waste application. Although some depression in yields occurred with
the higher rates of sludge, differences were probably not significant
since yields were variable. Levels of Zn were about twice as high
with ZnSOn and sludge treatments applied for 3 years; concentrations
with compost were similar to check values. Concentrations of Ni were
2 to 3 times higher with sludge than with other treatments. As in
corn grain, levels of Cd were slightly higher with sludge but less
than 1 ppm.
4. Results in 1975
Soil samples from treated plots were extracted with a DTPA solution
according to the procedure outlined by Lindsay and Norvell (10).
Based on previous experience this extractant removes about half as
much Zn, Cu, and Cd from soil as 0.5 ^N HC1; lesser amounts of Ni and
Pb are extracted. Results show that similar amounts of Zn were
recovered from plots amended in 1971 with ZnS04, compost, and sludge
(Table 16). However, after multiple applications, considerably less
Zn was extracted from compost-treated soils than from the ZnSO^ or
sludge plots. Possibly the complexing capacity of the compost for Zn
is responsible. Whereas repeated application of each treatment
increased extractable Zn from three- to sevenfold, the other heavy
metals were increased only two- to threefold.
Forage yields of sweet corn were not appreciably affected by ZnSOi+ or
waste treatments applied in 1971 (Table 17). In contrast to previous
years, yield increases of marketable ears were not obtained with
increases in rate of compost application. This might be due to ample
moisture during the growing season which probably negated any benefit
30
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from the organic wastes in terms of moisture relationships. No toxic
effects of Zn were evident even where repeated applications of ZnSO^
totaled 1,440 kg of Zn/ha.
Concentrations of Zn in corn forage from plots amended with compost
and sewage sludge were higher than in 1974 (Table 17); levels in
ZnSO^-treated plots were similar. No differences in grain Zn were
found as a result of treatment and levels were comparable to those in
crops of previous years. Concentrations of Cd were higher in 1975 in
both forage and grain from plots receiving sewage sludge. As in
previous years, Pb and Ni concentrations were not increased as a
result of organic waste application.
In 1975 the bean cultivar 'White Half Runner' was replaced with
'Contender,1 a true bush bean. The change was made to determine
whether the sensitivity of the 'White Half Runner' to Zn would also
apply to another cultivar. Other studies have shown that varietal
differences ranging from three- to tenfold may occur in terms of
tolerance to toxic levels of metals. Yields of 'Contender' vines
were somewhat higher and pods lower than with the 1974 'White Half
Runner' crop (Table 18). This may have been due to the later harvest
of more mature beans in 1974. Despite this difference in maturity
and cultivar, response to ZnSOi+ and the waste products was quite
similar. Yields of vines and pods were reduced slightly with the
residual ZnS04 and markedly with the repeated treatment. Again,
compost effects were negligible. Lowest yields were obtained with
multiple applications of sludge due at least in part to the lower
soil pH values associated with these treatments.
Trends in heavy metal concentrations in beans were similar to those
in 1974 (Table 15). Residual Zn availability from ZnSC% and sewage
sludge was similar as manifested in vine and pod concentrations.
However, repeated treatments resulted in higher Zn levels with sludge
due likely to lower soil pH. Whereas Zn concentrations increased
with rate of Zn as ZnSOn, levels with sewage sludge were not related
to rate. Despite the application of 1,440 kg/ha of Zn in compost,
concentrations were only slightly in excess of check values in vines
and pods.
Copper concentrations were slightly higher in beans grown on sludge-
treated plots with no differences between residual and repeated
application. Levels of Cd were highest with sludge, especially in
vine tissue. Lead concentrations were somewhat higher in vines but
not in pods from sludge-amended plots. As in 1973 and 1974, concen-
trations of Ni were higher with sludge, especially in pods.
34
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C. HEAVY METAL CONTENT OF SEVERAL VEGETABLE SPECIES
GROWN IN SOIL AMENDED WITH SEWAGE SLUDGE
Since the previous study indicated that corn and beans differ in
capacity to accumulate Zn and other heavy metals from municipal
waste-amended soils, the present study compared response of several
other vegetables to heavy metals contained in two sewage sludges
differing in composition (5).
Anaerobically digested sewage sludges from Tuscumbia and Decatur,
Alabama, were each applied at a rate of 112 metric tons/ha of dry
product in the fall of 1973 to an area next to the experimental site
of the previous study. Also, 100 kg each of N and K as NHi+NOs and
KC1, respectively, were applied and disked into the soil during the
spring of 1974 and 1975. Seeds of all vegetables (Tables 22 and 23)
were sown except peppers, tomatoes, and lettuce, which were trans-
planted. Overhead sprinkler irrigation was used to maintain adequate
soil moisture.
Vegetables were harvested from triplicate plots (3 by 5 meters) as
they matured and total yields were measured. Samples of leaves and
edible plant parts were taken midway through the growing season and
washed thoroughly with distilled water before drying at 80C. Grind-
ing and heavy-metal analysis were done as described in the previous
experiment. Soil samples were taken from the plots at about the same
time as the plant samples were taken. Portions of air-dried soil
were extracted with 0.5 1J HC1, 0.5 .N HN03, and DTPA and analyzed for
heavy metals as discussed earlier. Similarly, 5-gram portions of
air-dried Tuscumbia and Decatur sewage sludges were extracted with
each acid, DTPA, and water, and analyzed for the same heavy metals.
Less than 1% of the heavy metal content of the Tuscumbia or Decatur
sludges was extracted by water, whereas the acid extractants removed
from 49% to 100% (Table 19). Recovery with DTPA ranged from 9% to
46%. In general, dissolution of the metals by 0.5 N HC1 and 0.5 N_
HNOs was similar. Dissolution by the acids of the metals from the
Tuscumbia and Decatur sludges was in the order: Zn > Cu > Cd > Pb >
Ni and Zn = Cd > Cu > Pb > Ni, respectively. Dissolution in dilute
acid and DTPA differed within a particular sludge and also varied
from one sludge to another. In the case of Cu, this may be related
to the composition of the organic component of the sludge which is
probably responsible for complexing or bonding of Cu.
36
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Soil samples taken in 1974 from plots amended with sewage sludge were
similarly extracted (Table 20). As with the sludge, 0.5 ,N HC1 and
0.5 _N HNOs extracted similar amounts of heavy metals from soil. Most
of the Cu, Zn, Cd, Ni, and Pb in the soil amended with Decatur sludge
was extracted; lesser amounts were recovered from soil treated with
Tuscumbia sludge. This probably reflects the difference between
these waste products with regard to chemical forms of the elements,
types of bonding, and rate of organic matter decomposition. Applica-
tion of Tuscumbia sludge to the soil appeared to reduce the solubil-
ity of Cu, Zn, Cd, Ni, and Pb, but the solubility of Ni and Pb in
Decatur sludge increased after soil application. Recovery of metals
by acid extraction was slightly greater in 1975, suggesting an increase
in plant availability (Table 21). Although recovery of all metals
was less with DTPA than with acid, patterns were similar.
Yields of most vegetable species grown in 1974 were relatively unaf-
fected by sludge application (Table 22). However, tomato yields
increased from 23 to 30 kg and summer squash from 43 to 73 kg/plot
with Tuscumbia sludge. Yields with Decatur sludge were slightly
lower. Favorable response to municipal waste products also has been
reported by Terman and Mays (17), Hortenstine and Rothwell (8), and
Giordano, Mortvedt, and Mays (7). Application rates of garbage
compost or sewage sludge up to 400 metric tons/ha resulted in yield
increases of various crops in these studies.
Except for the leafy vegetables, radish and turnip roots were the
greatest accumulators of Zn and Cd. Highest concentrations of Zn
were found in lettuce, spinach, and radish leaves, and content of Cu
was high in lettuce, tomato, squash, and pepper leaves. Among the
leafy vegetables, lettuce was the greatest accumulator of Zn, Cu, and
Cd. Other investigators (12, 15) have also reported that heavy metal
content of leaf tissue is generally higher than in roots, seeds, or
fruits of vegetables.
Cadmium concentrations were higher with Decatur than with Tuscumbia
sludge, especially in lettuce and the root crops. Although slight
increases in Ni concentrations occurred with applied sludge, no
significant species differences were noted. Concentrations of Pb
were determined but not reported, since there was little variation
due to waste treatment. Levels in leaf tissue were normally higher
than in fruits or roots but species differences were not significant.
Possibly because of limited mobility of these elements in plants and,
therefore, restricted translocation to the reproductive parts, vege-
tables consumed as fruits or seed pods may be relatively free from
heavy metal contamination.
Yields of most plant species grown in 1975 were lower than in 1974
(Table 23). An extremely wet season in 1975 resulted in uncontrollable
weed and disease problems, thus necessitating an early termination of
38
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TABLE 22. TOTAL YIELD AND CONCENTRATIONS OF HEAVY METALS IN VEGETABLES,
AS AFFECTED BY SLUDGE TREATMENT (1974).
Species
Beans
(Phaseolus
limensis)
Okra
(Hibiscus
esculentus)
Peppers
(Capsicum
spp.)
Tomato
(Ly copersioon
eseulentum Mill.
Squash
(Cuourbita
pepo L.)
Turnip
(Brass ica
rapd)
Radish
(Raphanus
sativus L.)
Kale
(Brass ica
oleracea)
Lettuce
(Lactuca
sativa L.)
Spinach
(Spinacia
oleraoea)
Treatment
None
Decatur
Tuscumbia
None
Decatur
Tuscumbia
None
Decatur
Tuscumbia
None
Decatur
Tuscumbia
None
Decatur
Tuscumbia
None
Decatur
Tuscumbia
None
Decatur
Tuscumbia
None
Decatur
Tuscmubia
None
Decatur
Tuscumbia
None
Decatur
Tuscumbia
Yield,
kg/plot
7
7
6
12
11
11
23
25
20
23
29
30
43
67
73
13
14
13
11
11
13
__.
__
Fruit or root cone.
ppm
Zn
21
31
28
40
61
43
23
41
31
15
24
20
47
83
93
39
133
73
48
149
121
_
-
-
_
-
-
_
-
-
Cu
7.9
7.6
7.4
9.2
9.0
8.3
10.4
13.4
10.5
3.4
3.8
2.9
12.8
15.3
12.8
5.5
8.9
6.5
3.2
3.8
3.3
Cd
0.04
0.23
0.07
0.13
0.60
0.16
0.09
0.40
0.14
0.12
0.39
0.20
0.03
0.20
0.15
0.42
1.30
0.42
0.29
0.92
0.33
__
Ni
1.3
2.7
1.8
0.7
0.7
0.7
1.0
2.3
1.6
1.8
3.3
0.7
0.9
2.6
1.6
1.8
2.8
2.1
3.0
3.7
2.6
_
-
-
_
-
-
_
-
-
Leaf concentration
ppm
Zn
40
179
95
41
94
55
68
143
92
49
77
55
93
233
226
52
194
96
56
275
271
33
161
113
71
212
336
168
163
225
Cu
6.
7.
5.
6.
10.
7.
19.
21.
18.
19.
22.
18.
14.
19.
15.
6.
9.
7.
5.
7.
3.
6.
8.
7.
12.
22.
21.
9.
12.
10.
0
8
8
9
0
1
0
0
0
0
0
0
0
0
0
3
4
3
5
5
8
0
1
6
9
8
0
1
7
0
Cd
0.46
1.70
0.55
0.59
2.00
0.59
0.71
2.70
0.76
0.66
2.10
0.75
0.34
0.63
0.36
0.59
2.60
0.59
0.92
3.10
0.88
0.63
2.30
0.63
1.00
8.60
3.00
1.00
2.80
0.84
Ni
2.6
3.5
2.4
1.9
2.8
1.8
1.7
2.7
2.1
1.5
2.3
1.6
1.7
4.0
2.2
2.9
4.0
2.9
3.9
6.0
5.1
1.8
3.5
2.4
2.2
3.8
3.9
2.3
2.9
2.1
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the experiment. None of the vegetables grown in 1975 responded to
sludge amendment.
Concentrations of Zn, Cd, and Ni were slightly higher in both fruit
and leaf tissue in 1975 than in 1974. Levels of these heavy metals
were also higher in the plants grown on the check plots, possibly as
a result of the drop in soil pH from 6.4 in 1974 to 5.8 in 1975.
Cadmium increased in all species grown on plots receiving Decatur
sewage sludge. However, there was little indication that the Cd
present in Tuscumbia sewage sludge was available for plant uptake,
since concentrations in treated plants were comparable to those in
plants grown in untreated plots. This might be explained by the
higher total and extractable content of Cd in the Decatur waste
material.
Heavy metal uptake was consistently higher from Decatur than from
Tuscumbia sewage sludge with all vegetables. Even though the total
Zn content of the Tuscumbia sludge (3,640 ppm) was higher than that of
the Decatur sludge (1,840 ppm), uptake was greater from the latter.
Generally, plant availability of the heavy metals contained in the
waste materials was not related to either the total content or the
fraction extracted by acid or DTPA. Uptake results (Tables 22 and
23) relate well to soil extraction data (Tables 20 and 21), which
show that a greater percentage of all metals was extracted by 0.5 Ifl
HCl or HN03 from the Decatur sludge. Furthermore, slightly higher
heavy metal concentrations in plants in 1975 than in 1974 were
associated with greater recovery from amended soil in 1975 by acid
extraction.
43
-------
D. INFLUENCE OF SOIL HEATING ON PLANT AVAILABILITY
OF HEAVY METALS APPLIED IN MUNICIPAL SEWAGE SLUDGE
Several beneficial uses of waste heat from nuclear and fossil fueled
power production have been suggested. One outlet being considered is
soil heating which in some instances could extend the growing season
of certain crops. The objective of the present study was to determine
whether soil heating affects release of heavy metals from sludge-
amended soil by increasing the rate of organic matter decomposition.
If there is a significant increase in rate, plant availability of
heavy metals could be increased, the result being temporary toxicity
before reversion to less-soluble forms.
Municipal sewage sludge from Decatur, Alabama, was applied to Sango
silt loam (pH 5.1) at a rate of 224 metric tons/ha in the fall of
1974. Electric heating cables were installed at a depth of 30 cm and
thermostatically controlled to heat the soil to a temperature of 27C
(with a total heating capacity of 107 watts/meter2). Cables were
also installed in an unamended plot. Ammonium nitrate and KC1 were
applied uniformly over the untreated and sludge-treated plots to
supply 100 kg each of N and K/ha. Lettuce, bell peppers, pole beans,
sweet corn, and summer squash were planted in April 1975. Yields
were recorded throughout the growing season. Soil and plant samples
were taken during midsummer for analysis of Zn, Cd, Cu, Ni, and Pb.
Yields of all crops except sweet corn were reduced by soil heating
with or without sewage sludge (Table 24). Corn yields were not
affected by heating. Sludge application resulted in higher yields of
all crops without soil heating. Although corn and squash yields were
also increased with sludge in heated soil, yields of lettuce, peppers,
and beans were slightly lower.
Among the vegetables being investigated, lettuce was the greatest
accumulator of most of the heavy metals; corn leaves were high in Zn
and Cd, but the kernels were not excessively high (Table 25). Soil
heating had no consistent effect on heavy metal concentrations except
for Cd. Concentrations of Cd were higher in both leaf and fruit
tissue of all species grown on the heated than on the nonheated check
plots. Since soil heating did not result in higher Cd concentrations
where sludge was applied, it appeared that the higher concentrations
in plants from the heated checks were related to release of soil Cd.
However, soil extraction with both DTPA and 0.5 _N HC1 resulted in
greater recovery of all heavy metals from heated than from nonheated
soils regardless of sludge application (Table 26).
44
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SECTION VI
GREENHOUSE POT STUDIES
A. PLANT UPTAKE OF HEAVY METALS FROM SEWAGE SLUDGE
AS AFFECTED BY SOIL pH
Although the availability of Zn to plants decreases with rise in soil
pH, the literature suggests that pH has less effect on the availabil-
ity of Cd and other heavy metals. The purpose of this greenhouse
experiment was to determine whether liming an acid soil significantly
depresses uptake of heavy metals present in anaerobically digested
sewage sludge.
Mountview silt loam was limed to pH values of 5.0, 6.0, and 7.0 with
a 4:1 mixture of CaCOa and MgC03. The following nutrients were mixed
with 2 kg of soil at the rates indicated: NHuN03400 mg of N;
concentrated superphosphate200 mg of P; KaSOit200 mg of K. Decatur
and Tuscumbia sewage sludges were also mixed with the soil to provide
both 40 and 200 grams of dry matter per pot. An inorganic heavy
metal supplement was mixed with the soil in a third series of pots to
supply Zn, Cu, Cd, Ni, and Pb at rates equal to those provided by 40
grams of the Tuscumbia sewage sludge. Mustard (Sinapis alba) seeds
were sown in January 1975, and thinned to 12 plants per pot. Leaves
were harvested three times over a period of 10 weeks, allowing enough
time for regrowth between harvests. Plant tissue was dried, weighed,
crushed, and analyzed for heavy metal content.
Mustard yields increased with soil pH among most treatments and
sludge rates (Table 27); Tuscumbia sludge was very toxic at the 200-
gram rate at all pH values. Inorganic heavy metals equivalent to 40
grams of Tuscumbia sludge were more toxic than the sludge at pH 5.0
only. Yields were highest at all pH values with Decatur sludge,
probably due in part to its liming effect.
Uptake of Zn varied inversely with soil pH. Although uptake was
sometimes higher with Decatur than with Tuscumbia sludge, concentra-
tion was less due to growth dilution. The higher Zn concentrations
associated with the Tuscumbia sludge treatment likely account for the
poor growth of mustard, especially at the high rate of application.
Toxicity was apparent when concentrations of Zn in the plant tissue
exceeded 500 ppm. This is in general agreement with other published
data.
Cadmium uptake was highest at pH 5.0, but differences between pH 6.0
and 7.0 were not great. The higher Cd content of the Decatur than of
the Tuscumbia sludge was reflected in higher plant uptake. Uptake of
Cu, Pb, and Ni was not affected by soil pH. Whereas Cu levels were
higher with Decatur than with Tuscumbia sludge, levels of Pb and Ni
were smaller with both sludge treatments.
48
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B. RESPONSE OF CORN TO Zn AND Cr IN MUNICIPAL
WASTES APPLIED TO SOIL
This experiment was conducted to determine if Zn and Cr in several
municipal waste products becomes available to plants after soil
incubation and successive cropping (13).
A greenhouse pot experiment was conducted using Hartsells fine sandy
loam from northern Alabama. This soil was limed to pH 5.5 and the
following supplemental nutrients were mixed with the soil in each pot
containing 3 kg of soil: 600 mg of N as NHaN03, 300 mg of P as
concentrated superphosphate, 200 mg of K as K2SOi+, and 20 mg of Mn as
MnSO^. The amounts of nutrients added in sewage sludge or compost
were in addition to the above nutrients.
The cropping sequence was: Crop 1planted immediately after waste
application and grown for 7 weeks; Crop 2planted after moist soil
incubation for 21 weeks at 25C and grown for 7 weeks; Crop 3similar
incubation for 36 weeks and grown for 7 weeks. The soils treated with
ZnSOij and Na2Cr207 were discarded after Crop 2. Before Crops 2 and 3
were planted the following nutrients were mixed with the soil per pot:
200 mg of N as NH4N03, 200 mg of P and 252 mg of K as KH2P04. An
additional 400 mg of N/pot as a solution of NHt+NOs was applied during
the growth period.
The three waste products were applied at rates of 15, 75, and 300
grams/3 kg of soil (11, 56, and 224 metric tons/ha), supplying 7 to
1,400 ppm of Zn and 1 to 1,360 ppm of Cr (Table 28). Fine ZnS04 and
Na2Cr2Ov were mixed with the soil alone and together in separate
series to provide 12, 60, 240, and 1,400 ppm of Zn and 1, 5, 20, 80,
and 320 ppm of Cr, respectively.
After each harvest the soil in each pot was core-sampled, air-dried,
and screened (20 mesh). The soil was extracted by 0.5 _N HC1 and by
DTPA. Two samples of air-dried sewage sludge obtained from municipal
plants equipped with secondary treatment facilities were used.
Sludge A (containing 1.36% Cr) from Sheffield, Alabama, was contami-
nated by apparent leakage of industrial waste into a municipal sewer
system; Sludge B (containing 0.05% Cr) was obtained from the Tuscumbia
plant. The garbage compost sample was obtained from the Johnson City,
Tennessee, compost plant. The composted product contained about 20%
sewage sludge.
Five plants of corn (cv. 'Funk's 4455') were grown per pot for 7
weeks during which deionized water was added to the soil daily to 0.3
atm moisture tension. Supplemental lighting was provided to maintain
a day length of 16 hours. After harvest the forage in triplicates of
each treatment was dried, weighed, and analyzed for Zn and Cr by
atomic absorption spectroscopy using the standard techniques.
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Yields from the three crops were not greatly affected by application
of Sludge A, even though this product contained relatively high Zn
and Cr concentrations (see Appendix). A decrease in yield was noted
at the highest application rate of Sludge B in Crop 1 only. This
apparent toxicity may have been caused by some unidentified compounds
found in used motor oils present in this product. Yields were higher
with the two highest compost rates in Crops 1 and 3 only.
Concentration of Zn in plant tissue increased with application rate
of all waste products in all crops. Concentrations were higher from
soils treated with Sludge A, followed by Sludge B and compost, the
same order as the amounts of Zn contained in these products. Thus,
Zn contained in these waste products was available to plants for a long
period in the soil. Sludge A contained a high level of Zn (1.4%),
but no toxicities were noted even at the highest application rates.
Concentrations of Zn in plant tops generally decreased from Crop 1 to
Crop 3 with the two high rates of comparable treatments, indicating
that the Zn in the wastes was becoming less available with time.
Lower Zn concentrations in Crop 2 could have been due to dilution
with the higher yield levels in this crop. Crop removals accounted
for less than 5% of the Zn contained in the wastes.
Concentrations of Cr in all three corn crops were not affected by
waste applications. The high Cr level in Sludge A resulted in a very
high application rate (1,360 ppm), yet neither plant growth nor Cr
uptake was affected by applications of this product. Thus, avail-
ability to the plant of Cr contained in these wastes applied to soil
is very low.
Forage yields (Table 29) decreased with ZnSOq. applications of 240 and
1,400 ppm of Zn in Crops 1 and 2 and with Na2Cr2Ov applications of
20, 80, and 320 ppm of Cr in Crop 1. Little growth resulted at the
1,400-ppm Zn and 320-ppm Cr rates. Including Na2Cr207 with ZnSO^ in
a separate treatment (data not shown) did not have any more dele-
terious effect on plant growth at any Zn rate. Toxicity to corn of
either Zn or Cr was not as pronounced in Crop 2, suggesting a reduc-
tion in the plant availability of each inorganic source with time.
Concentrations of Zn in corn tissue increased with ZnSO^ application
rate and were much higher than those in corn grown on waste-treated
soils at comparable Zn rates. Zinc concentrations in corn tissue
decreased from Crop 1 to Crop 2, thus reflecting a rapid fixation of
the applied ZnSO^ in less-available forms.
Chromium concentrations in plant tops were increased by the two
highest Na2Cr207 rates in Crop 1 and by the highest rate in Crop 2.
Little plant growth resulted at these Cr rates. Concentrations of Cr
in the growth-retarded corn were 5 ppm in Crop 1 and 9 ppm in Crop 2.
The narrow range in Cr concentrations in plant tops between normal
52
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and retarded growth suggests that Cr is toxic to plant roots but that
translocation of Cr to plant tops is limited.
Soil pH increased with application rate of all three wastes, espe-
cially with compost applications (Table 30). This is related to
relatively high contents of Ca and Mg. A decrease in soil pH was
noted with time in all treatments, which could be related to the
application of fertilizers to the soil prior to each crop. Soil pH
was not affected by applied ZnSO^ or Na2Cr207.
Levels of 0.5 _N HCl-extractable Zn and Cr in the soil after each crop
increased with application rate of each product. The order was
Sludge A > Sludge B > compost, the same order as their content of
these heavy metals. Extractable Zn and Cr did not change appreciably
with time, except that increased levels of both elements were noted
at the two highest rates of Sludge A. The percentage recovery of Zn
and Cr applied with these wastes by this extractant varied consid-
erably with time and application rate. Maximum recovery of Zn and Cr
was about 60% at the highest waste application rate.
The level of 0.5 N_ HCl-extractable Zn increased with ZnSOa applica-
tion rate from 5 to 1,305 ppm after Crop 1 and from 7 to 640 ppm
after Crop 2. Extractable Cr also increased with Na2Cr207 applica-
tion rate but the percentage recovery of applied Cr was lower than
that of Zn. Lower levels of extractable Zn and Cr after Crop 2
indicate fixation in the soil with time.
The level of DTPA-extractable Zn also increased with rate of applied
Zn (data not shown), but in each instance was lower than with 0.5 N:
HC1. The higher recovery by 0.5 N^ HC1 probably was due to degrada-
tion of some of the organic matter in the wastes as well as dissolu-
tion of some soil Zn by the acid extractant. Also, DTPA may not have
been able to compete with some organic ligands for the Zn applied
with these products. The level of Cr in the DTPA extracts was too
low to detect by the method used.
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C. RELATIONSHIP OF Zn AND Cd SUPPLY TO UPTAKE BY FESCUE
It has been claimed that sewage sludges containing Zn and Cd in
ratios less than 100 to 1 should not be applied to agricultural land
(2, 3). This rule is based on the premise that excess Zn prevents
toxic accumulations of Cd by first causing plant injury. This exper-
iment was conducted to determine whether varying the ratio of Zn to
Cd in the soil influences their mutual uptake.
Lakeland sand (pH 5.2) was fertilized preplant with 400 mg of N as
NHi+N03, 200 mg of P as concentrated superphosphate, and 200 mg of K
as K2S04 (2 kg of soil per pot). Chlorides of Zn and Cd were applied
in factorial combination at the rates shown in Table 31. Extra pots
were included to compare sewage sludges from Decatur and Florence,
Alabama, each applied at a rate of 200 grams of dry material per
pot. Another treatment contained Florence sewage sludge plus CdCla
to equal the Cd content of the Decatur sludge (Table 32). Tall
fescue (Festuca arundinacea Schreb., cv. 'Kentucky 31') was planted
and clippings from triplicates of each treatment were harvested at
monthly intervals over a 4-month period. An additional 200 mg of N,
100 mg of K, and 250 mg of a micronutrient mix, minus Zn, was applied
as a solution to the soil surface of all pots after the third harvest.
The oven-dried clippings from each harvest were weighed, ground, and
analyzed for Zn and Cd content. Clippings from sludge-treated pots
were also analyzed for Cu, Ni, and Pb.
Dry matter production of fescue decreased with rate of Zn application
(Table 31); however, only the 100-mg rate of Cd resulted in decreased
yields. Yields were much higher in pots of soil amended with Decatur
and Florence sewage sludges (Table 32). Since all pots received
seemingly adequate amounts of N, P, K, and micronutrients, as well as
water, there is no obvious explanation for the enhanced growth with
sewage sludge applications.
Uptake of Zn increased with 100 mg of Zn but decreased in some cases
with 500 mg as a result of toxicity to the plant preventing additional
uptake (Table 31). Level of Cd applied to the soil did not affect
plant Zn concentration consistently. Increased Cd rate depressed Zn
concentration in the fescue only at the 100-mg Zn rate.
Uptake and concentration of Cd increased with rate of applied Cd but
concentrations were unaffected by Zn application. These results
suggest that Cd concentrations greater than about 100 ppm in fescue
may be toxic to plant growth. However, rather high concentrations
can occur in fescue without visual indication of toxicity.
The greater yields from the sludge-amended pots occurred even though
rates of Zn applied in the sludge were high (Table 32). Apparently
plant availability of Zn in the sewage sludges was much less than
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that of ZnCla. Also, the availability of Zn in the Decatur sludge
was less than in the Florence sludge. Likewise, Cd availability was
less from the organic wastes than from CdCl2. Equalizing the Cd
content in Florence sludge to that of Decatur sludge with CdCl2
resulted in higher concentrations and uptake of Cd.
Plant uptake of Cu was somewhat higher from soil treated with
Florence than with Decatur sludge, while Pb uptake was similar.
Although Ni content of Florence sludge was less than twice the
content of the Decatur sludge, plant uptake was more than three times
as great. Based on Zn, Cu, and Ni uptake, it would appear that these
elements are present in a more available form in the Florence than in
the Decatur sludge. Differences in plant availability of heavy
metals in these sludges possibly could be related to the method of
waste treatment; Florence uses an activated sludge process, while
Decatur uses the anaerobically digested sludge process.
59
-------
SECTION VII
SOIL MOBILITY STUDIES
A. NITROGEN EFFECTS ON MOBILITY AND PLANT UPTAKE OF HEAVY METALS
IN SEWAGE SLUDGE APPLIED TO SOIL COLUMNS
There is current concern that land disposal of large quantities of
sewage sludge on some soils may result in heavy metal contamination
of ground water. However, there is little information in the litera-
ture regarding mobility of metals such as Cd, Cr, Ni, and Pb. The
purpose of these experiments was to determine the possible effect of
N fertilizer on the movement of several heavy metals in soil under
leaching conditions (6).
Leaching columns consisting of 60-cm sections of 15-cm plastic well
casings were packed from bottom to top with 800 grams of coarse
quartz sand, 1,200 grams of fine quartz sand, and 10 kg of a mixture
consisting of eight parts Ennis fine sandy loam (pH 5.4) and two
parts fine quartz sand. The resulting systems contained about 40%
pore space. This soil contained 1.2X organic matter, 184 ppm of Bray
No. 2 extractable P, and had a cation exchange capacity (CEC) by
ammonium ion displacement of 5.6 meq/100 grams. An additional 5 kg
of the same soil-sand mixture, containing the following nutrients,
was added to the columns: P500 mg as concentrated superphosphate,
and K300 mg as K2SOit. A 0.42-cm mesh plastic screen was used to
separate the fertilized soil from the nonfertilized soil. Nitrogen
as granular urea and sulfur-coated urea (SCU) containing 36.7% N and
21% S was also mixed with the top 5 kg of soil in some columns at a
rate of 750 mg (Table 33). Elemental S plus granular urea was applied
to other columns in a similar manner to simulate rates of N and S
from the SCU. Other treatments included Tuscumbia sewage sludge
mixed with the top 5 kg of soil to approximate an application rate of
224 metric tons/ha of dry matter and heavy metals applied as inorganic
salts at rates equivalent to those supplied in the sewage sludge
(Zn840 mg; Pb640 mg; Cr215 mg; Ni117 mg; and Cd19 mg).
Three replicate columns of each treatment were planted to fescue and
maintained in the greenhouse. Enough deionized water was added to
all columns after planting and during the experiment to maintain good
growth. All columns were leached with the equivalent of 12 cm of
deionized water at 4, 8, and 12 weeks after planting. A vacuum
system exerting a suction of about 0.2 atm at the bottom of each
column was used to expedite leaching. Grass clippings were harvested
after 6, 10, and 14 weeks, dried at 70C, and weighed. After the last
harvest, each soil column was carefully removed intact from the
casing and sampled at 1-cm increments below the screen which origi-
nally separated the treated from the nontreated soil. Samples of
soil were extracted with 0.5 JJ HCl. Leachate, clippings, and soil
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extracts were analyzed for Zn, Cd, Cr, Ni, and Pb by atomic absorp-
tion or flameless atomization when elemental concentration was below
the detection limit of the flame.
A second series of leaching columns was prepared using a similar
technique but with a 1:1 mixture of quartz sand and Decatur silt loam
(pH 5.2). The sand was added to the soil to accelerate the rate of
leaching. The Decatur silt loam contained 1.8% organic matter, 168t
ppm of Bray No. 2 extractable P, and had a CEC of 9.7 meq/100 grams.
Nutrients and other amendments were mixed with the upper 5 kg of
sand-soil mixture. Treatments in duplicate soil columns are shown in
Table 34. One replicate of each treatment was left fallow and the
second planted to 'Kentucky 31' fescue. Leachate was collected as in
the previous experiment at 4, 8, -and 12 weeks after planting and the
cropped columns were clipped after 6, 10, and 14 weeks. The columns
were sectioned and the soil extracted as previously described.
Despite the adding of quartz sand to the Ennis soil, percolation of
water through the soil columns was extremely slow, even when vacuum
was applied. This was probably a result of soil compaction which may
have been related to the high percentage of silt in the soil. The
volume of leachate recovered from the columns after adding 2,000 mg
ranged from 200 to 1,000 ml. Analyses of the leachate showed that
the concentrations of Zn, Cd, Cr, Ni, and Pb were not increased by
soil application of sewage sludge or inorganic salts, indicating that
none of the applied heavy metals leached entirely through the non-
treated portion of the soil column (45 cm).
Data in Table 33 further indicate that little downward movement of
the heavy metals occurred as a result of the three leachings.
Although differences were small, mobility of heavy metals applied in
the sludge appeared to be less than that of the inorganic sources.
In general, Cd and Pb were less mobile than the others. Despite the
higher stability constant of manure and other fecal complexes than of
soil organic matter complexes, it appears that metal complexes formed
in municipal sewage sludges are not readily leached from the soil, at
least over short periods.
Heavy metal movement was not enhanced by application of N fertili-
zers. Any anion effects on cation movement may have been negated by
the poor soil structure which prevented free water flow. Further,
denitrification of the applied N may have occurred as a result of
waterlogged conditions that prevailed for several hours after each
leaching.
There was no indication that urea or SCU influenced heavy metal
uptake other than as a result of increased growth in response to N
(Table 34). A slight yield increase as well as uptake of Zn, Cd, Pb,
and Ni was obtained in the presence of elemental S with urea plus the
heavy metals. This increase may have been due to a slight localized
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acidification in the soil upon oxidation of S, although gross pH
measurements at the end of the study did not show a decrease.
Apparently sludge applied with urea was either toxic to the grass or
it immobilized most of the N, based on the low dry matter production.
Results of an earlier study (7) indicated that high rates of sludge
were toxic to string beans. This was attributed to excessive Zn
uptake. Despite the high Cr content of the sludge, uptake was neg-
ligible, as was observed previously (13). Grass clipping yields
increased slightly with applied heavy metals despite the much greater
uptake of Zn, Cd, and Ni.
Although the percolation rate of water through the columns of Decatur
soil-sand mixture was much greater than that through the Ennis soil-
sand mixture, the leachate contained less than 20 parts per .billion
(ppb) of Pb and Ni, and concentrations of Zn, Cr, and Cd were non-
detectable. Leachates from cropped and fallow columns were compara-
ble in heavy metal concentration, indicating that roots had little
effect on metal movement. In general, concentrations of Cd, Cr, Ni,
and Zn were lower in the Decatur than in the Ennis soil (Tables 33
and 35).
Movement of most heavy metals was generally greater in the Decatur
soil when the metals were applied as inorganic salts (Table 35).
Mobility of heavy metals contained in sludge was negligible. Move-
ment of metals in cropped and fallow soils was similar, although
concentrations in the cropped soil tended to be consistently lower,
possibly due to plant uptake.
Dry weight and cumulative heavy metal uptake of fescue were similar
to that in the previous experiment (Table 36). Application of sludge
alone resulted in poorer growth than application of sludge with urea.
Since the poor growth apparently was not related to Zn, Cd, Cr, Ni,
or Pb toxicity, it is possible that the combination of Mn present in
the sludge (253 ppm) and the excessive moisture in the soil following
leaching could have resulted in Mn toxicity, although Mn concentra-
tions in the fescue were not determined.
64
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B. MOVEMENT OF HEAVY METALS IN SOILS
FROM MUNICIPAL WASTES AND INORGANIC SOURCES
The previous experiment indicated that very little heavy metal move-
ment occurred in soils leached periodically in the greenhouse for 3
months. The present experiments were initiated to determine the
extent of metal movement in soil under natural conditions of pre-
cipitation and temperature fluctuation over an extended period.
Ennis fine sandy loam (pH 5.4) was placed in bins of the TVA rhizotron-
lysimeter facility (16) in the spring of 1973. Unreplicated treat-
ments consisted of (i) check, (ii) orthophosphate (250 kg of P/ha),
(iii) orthophosphate plus inorganic heavy metals, (iv) polyphosphate
(250 kg of P/ha), (v) polyphosphate plus inorganic heavy metals, (vi)
Tuscumbia sewage sludge (224 metric tons/ha), (vii) sludge plus
orthophosphate, (viii) sludge plus polyphosphate, (ix) Johnson City
compost (224 metric tons/ha), and (x) compost plus orthophosphate.
All amendments were incorporated into the upper 15cm of soil. Sweet
corn was planted in each bin followed after harvest by a crop of string
beans. All treatments except the inorganic heavy metals were reapplied
in April 1974 and the bins cropped as before. Leachate was collected
throughout the experiment for heavy metal assay. After the beans
were harvested in mid-October 1974, soil borings were taken from all
bins to a depth of 60 cm. Samples of soil were extracted with 0.5 IJ
HC1 to estimate downward movement.
In general, movement of Zn, Cu, Cd, Cr, Ni, and Pb was similar from
all heavy metal sources and with ortho- or polyphosphate fertilizers.
Apparently the polyphosphate had no effect on mobilization of the
metals by solubilization or sequestration. Approximately 80% of the
applied heavy metals remained in the top 15-cm (data not shown).
Levels of Zn, Cu, and Cd slightly above the check values were
detected to a depth of 120 cm in the sludge-treated soils. Analyses
of the leachates from these and other bins confirmed that the metals
had not moved through the entire soil profile, however.
Due to the slow rate and irregular percolation of water through the
soil in this experiment, it was impossible to evaluate conclusively
the mobility in soil of heavy metals from these organic and inorganic
sources. Therefore, the Ennis soil was replaced with Decatur silty
clay. Treatments included (i) check, (ii) Tuscumbia sewage sludge
(224 metric tons/ha), and (iii) Florence sewage sludge (224 metric
tons/ha). The sludge materials were incorporated into the upper
15-cm layer of soil as before. Duplicate bins were used for each of
these treatments. As in the previous experiment, the cropping
sequence was sweet corn followed by string beans. In addition to
collecting leachate from below each bin and sampling soil at varying
depths, porous ceramic tubes were installed horizontally in the soil
at depths of 15, 45, 75, and 120 cm for extraction of soil solution.
67
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Heavy metal concentrations in soil solution and leachate were moni-
tored from early spring of 1974 until mid-October of 1975 when soil
borings were taken.
Despite the superior drainage characteristics of the Decatur compared
with the Ennis soil, movement of heavy metals from the zone of appli-
cation was negligible. (Estimates of percolates expressed as percent-
ages of total rainfall plus supplemental irrigation were 40% for the
Ennis and 60% for the Decatur soil.) Acid-extractable levels of
heavy metals above check soil values were not observed beyond a depth
of 15 cm (data not shown). Zinc was the only heavy metal detected in
soil solution even from probes situated in the treated zone (15 cm).
Although concentrations of Zn were very variable, values at 15 cm
averaged about 0.4, 0.8, and 2.7 ppm in the check, Tuscumbia sludge-,
and Florence sludge-treated soil, respectively. Soil solution concen-
trations of Zn did not exceed check soil levels at greater depths
(45, 75, and 120 cm).
68
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SECTION VIII
REFERENCES
1. Carlson, C. W., and J. D. Menzies. Utilization of urban wastes
in crop production. BioSci. 21:561-564. June 1971.
2. Chaney, R. L. Crop and food chain effects of toxic elements in
sludges and effluents. In Recycling Municipal Sludges and
Effluents on Land. Proc. Joint Conf. Natl. Assoc. State Univ.
and Land-Grant Colleges, Washington DC. pp. 129-141. July
1973.
3. Chaney, R. L. Land application of sewage sludge: Benefits and
problems. J_n_ Proc. 1973 Lime and Fertilizer Conf., Delaware-
Maryland Plant Food Assoc. 5:15-23. 1973.
4. Chaney, R. L. Recommendations for management of potentially
toxic elements in agricultural wastes. In Factors Involved in
Land Application of Agricultural and Municipal Wastes, ARS-USDA.
pp. 97-120. 1974.
5. Giordano, P. M., and D. A. Mays. Yield and heavy metal content
of several vegetable species grown in soil amended with sewage
sludge. In Biological Implications of Metals in the Environ-
ment, 15th Annual Hanford Life Science Symposium. 1976. (In
press).
6. Giordano, P. M., and J. J. Mortvedt. Nitrogen effects on
mobility and plant uptake of heavy metals in sewage sludge
applied to soil columns. J. Environ. Qual. 5:165-168. 1976.
7. Giordano, P. M., J. J. Mortvedt, and D. A. Mays. Effect of
municipal wastes on crop yields and uptake of heavy metals. J.
Environ. Qual. 4:394-399. 1975.
8. Hortenstine, C. C., and D. F. Rothwell. Use of municipal
compost in reclamation of phosphate-mining sand tailings. J.
Environ. Qual 1:415-418. 1972.
9. Kochtitzky, 0. W., W. K. Seamon, and J. S. Wiley. Municipal
composting research at Johnson City, Tennessee. Compost Sci.
9:5-16. 1969.
10. Lindsay, W. L., and W. A. Norvell. Development of a DTPA
micronutrient soil test. In Agronomy Abstracts, p. 84. 1969.
11. Mays, D. A., G. L. Terman, and J. C. Duggan. Municipal com-
post: Effects on crop yields and soil properties. J. Environ.
Qual. 2:89-92. 1973.
69
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12. Mclntyre, D. R., and W. J. Silver. Trace element uptake by
field-grown food plants fertilized with waste water sewage
sludge. In Agronomy Abstracts. p. 29. 1975.
13. Mortvedt, J. J., and P. M. Giordano. Response of corn to zinc
and chromium in municipal wastes applied to soil. J. Environ.
Qual. 4:170-174. 1975.
14. Purvis, D., and E. J. MacKenzie. Effect of applications of
municipal compost on uptake of Cu, Zn, and B by garden vege-
tables. Plant Soil. 39:361-371. 1973.
15. Simon, P. W., R. L. Chaney, and E. Epstein. Heavy metal con-
tents of selected vegetable crops grown on sewage sludge and
composted sewage sludge-amended soil at two pH's. In Agronomy
Abstracts, p. 39. 1974.
16. Soileau, J. M., D. A. Mays, F. E. Khasawneh, and V. J. Kilmer.
The rhizotron-lysimeter research facility at TVA, Muscle Shoals,
Alabama. Agron. J. 66:828-832. 1974.
17. Terman, G. L., and D. A. Mays. Utilization of municipal solid
waste compost: Research results at Muscle Shoals, Alabama.
Compost Sci. 14:18-21. 1973.
18. Terman, G. L., J. M. Soileau, and S. E. Allen. Municipal waste
compost: Effects on crop yields and nutrient content in green-
house pot experiments. J. Environ. Qual. 2:84-89. 1973.
19. Van Loon, J. C. Mercury contamination of vegetation due to the
application of sewage sludge as a fertilizer. Environ. Letters
6:211-218. 1974.
70
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SECTION IX
PUBLICATIONS
The following publications have resulted from work supported by this
project:
1. Terman, G. L., and D. A. Mays. 1973. Utilization of municipal
solid waste compost: Research results at Muscle Shoals, Alabama.
Compost Sci. 14:18-21.
2. Mays, D. A., G. L. Terman, and J. C. Duggan. 1973. Municipal
compost: Effects on crop yields and soil properties. J.
Environ. Qual. 2:89-92.
3. Terman, G. L., J. M. Soileau, and S. E. Allen. 1973. Municipal
waste compost: Effects on crop yields and nutrient content in
greenhouse pot experiments. J. Environ. Qual. 2:84-89.
4. Mortvedt, J. J., and P. M. Giordano. 1975. Response of corn
to zinc and chromium in municipal wastes applied to soil. J.
Environ. Qual 4:170-174.
5. Giordano, P. M., J. J. Mortvedt, and D. A. Mays. 1975. Effect
of municipal wastes on crop yields and uptake of heavy metals.
J. Environ. Qual. 4:394-399.
6. Giordano, P. M., and D. A. Mays. 1976. Yield and heavy metal
content of several vegetable species grown in soil amended with
sewage sludge. In Biological Implications of Metals in the
Environment, 15th Annual Hanford Life Science Symposium. (In
press).
7. Giordano, P. M., and J. J. Mortvedt. 1976. Nitrogen effects
on mobility and plant uptake of heavy metals in sewage sludge
applied to soil columns. J. Environ. Qual. 5:165-168.
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1 REPORT NO.
EPA-600/2-77-014
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
EFFECT OF LAND DISPOSAL APPLICATIONS OF MUNICIPAL
WASTES ON CROP YIELDS AND HEAVY METAL UPTAKE
5. REPORT DATE
April 1977 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
P. M. Giordano and D. A. Mays
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
National Fertilizer Development Center
Tennessee Valley Authority
Muscle Shoals, Alabama 35660
10. PROGRAM ELEMENT NO.
1DC618, (SOS#5, Task 02)
11. CONTRACT/GRANT NO.
EPA-IAG-D4-0415
12. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory--Cin.,OH
Office of Research and Development
U. S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final, 1969-1975
14. SPONSORING AGENCY CODE
EPA/600/14
15. SUPPLEMENTARY NOTES
Project Officer: Carlton C. Wiles. 684-7881
16. ABSTRACT
This report provides the cumulative data acquired from 1969 through 1975 from field
and greenhouse investigations pertaining to the effects on selected soils and
plants from municipal compost and sewage sludge applications. Multiple applications
of composted municipal refuse resulted in satisfactory crop growth with only
moderate increase of some heavy metals in plant tissue. In contrast, lower rates
of several domestic sewages resulted in significant uptake of certain metals,
especially in more sensitive species, such as leafy vegetables and string beans.
Plant availability of metals derived from sewage seems to be related to product
matrix rather than to total metal content. Little downward movement of heavy
metals was observed under conditions of heavy leaching in the greenhouse or natural
rainfall outdoors.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COS AT I Field/Group
Waste Treatment
Refuse Disposal
Sewage Disposal
Soil Properties
Plant Growth
Accumulation
Toxicity
leavy Metal
.ands Waste Disposal
lunicipal Solid Waste
Sewage
teavy Metal Accumulation
Plant Toxicity
Soil Toxicity
13B
8. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
83
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
73
U. S. GOVERNMENT PRINTING OFFICE 1977-757-056/5570 Region No. 5-11
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