United States
Environmental Protection
Agency
Water Engineering
Research Laboratory
Cincinnati OH 45268
r/v<
Research and Development
EPA/600/S2-85/095 Sept. 1985
Project Summary
Use of Sewage Sludge for
Forest-Tree Seedling
Production
D. H. Lambert, T. C. Weidensaul, D. C. Borger, and L. H. Rhodes
Research was conducted to develop
the use of sewage sludge on non-
foodchain crops such as forest trees.
The study determined the beneficial
and harmful effects of using dewatered,
digested sewage sludge in (1) estab-
lishment and growth of transplanted,
bare-root, coniferous seedlings grown
in the field as Christmas trees, (2) tree
seedling production in a conventional
outdoor nursery, (3) containerized pro-
duction of forest tree seedlings, and
(4) formation and survival of mycor-
rhizae on forest trees and soybeans.
The copper requirements of conifers
were also investigated.
Sludge was evaluated according to
the abundance of required nutrients it
provides compared with those supplied
by conventional fertilization practices.
Toxtcities of various elements were de-
termined, as were sludge-induced nu-
trient deficiencies associated with vari-
ous sludge types and application rates.
Optimum loading rates were deter-
mined to maximize seedling survival
and growth in the field and to minimize
the risks associated with ammonia and
heavy-metal toxicfties.
This Project Summary was developed
by EPA's Water Engineering Research
Laboratory. Cincinnati, OH. to announce
key findings of the research prof act that
is fully documented in a separate report
of the same title (see Project Report
ordering information at back).
Introduction
Two major environmental problems
that have received much public atten-
tion in recent years are the disposal of
sewage sludge and the deterioration of
soils. Solving one problem may ulti-
mately solve the other.
Treated sewage sludge has been ap-
plied to agricultural soils and to toxic
spoil materials remaining from strip
mining. Though the fertilizer value of
sewage sludge has been established,
many questions remain unanswered
about its safety, efficiency, and best use
in land disposal.
A more efficient, effective alternative
to using sewage sludge for food and
forage crop production may be to use it
for producing non-foodchain crops
such as forest trees for fiber, beauty,
recreation, fuel, construction, etc. Trees
have diverse uses, both presently and in
the immediate future. Containerized
seedling production will become a rou-
tine practice in the future. Sludge appli-
cation to such non-foodchain crops may
be particularly useful for sludges that
are difficult to dispose of.
This study was undertaken to deter-
mine the beneficial and harmful effects
of using dewatered, digested sewage
sludge in (1) establishment and growth
of transplanted, bare-root, coniferous
seedlings grown in the field as Christ-
mas trees, (2) tree seedling production
in a conventional outdoor nursery,
(3) containerized production of forest
tree seedlings, and (4) formation and
survival of mycorrhizae on forest
trees and soybeans. The copper
requirements of conifers.were also
investigated.
Sludge was evaluated according to
the abundance of required nutrients it
provides compared with those supplied
by conventional fertilization practices.
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Toxicities of various elements were de-
termined, as were sludge-induced nutri-
ent deficiencies associated with various
sludge types and application rates. Op-
timum loading rates were determined
to maximize seedling survival and
growth in the field and to minimize the
risks associated with ammonia and
heavy-metal toxicities.
Perennial crops such as forests and
Christmas trees require different pro-
duction management techniques from
field crops and vegetables. Similarly,
their responses to environmental
stresses and biologic influences are in
many ways unlike those of cultivated
crops used as food and feed bases. Al-
though a great amount of sludge re-
search has been initiated in recent years
on field crops such as corn and soy-
beans, very little has concerned trees.
Because all plants differ in their growth
patterns and responses to stimuli,
sludge research on trees is unique, par-
ticularly in light of the lack of such re-
search.
For Christmas tree production, land is
prepared once every 8 or 10 years and
can be fertilized before or after planting.
In many cases, no fertilizers are added.
Thus sludge could be applied before
soil preparation to provide nutrients
that would be released more slowly
than from inorganic fertilizers.
In nursery bed seedling production,
lighter, sandier soils are usually se-
lected because of their better drainage
and properties as a rooting medium.
Such soils normally require supple-
ments of organic matter to maintain nu-
trient and water-holding capacity.
Production of containerized tree seed-
lings in greenhouses is a developing
and popular technology that now pro-
vides most of the privately planted
forest seedlings in some areas. Such in-
tensively grown trees require optimum
fertilization of their artificial rooting
medium.
Although sludge contains substantial
amounts of P, its availability to plants
may vary with the treatment method
used to remove it from wastewater and
stabilize it. In addition, toxic compo-
nents of sludge may affect plant uptake
of P by inhibiting the development and
activity of mycorrhizal fungi (root-
infecting symbionts).
Vesicular-arbuscular (VA) mycor-
rhizal fungi are known to improve plant
growth by increasing the uptake of plant
nutrients, particularly P. Spore genera-
tion of certain species of VA fungi has
been shown to be adversely influenced
by at least three heavy metals—Mn, Cu,
and Zn, which are often present in high
concentrations in sludge. Such inhibi-
tion of mycorrhizal fungus spore germi-
nation could result in limited
mycorrhizal development and could ul-
timately lead to poor plant growth.
Field-Grown Christmas Trees
Procedures
Two Christmas tree plantations were
established near Wooster, Ohio. One
was located on a good site with well-
drained silt loam previously cropped to
corn or hay, and one was placed on a
poorly drained silt loam recently
cleared of large hardwood trees. During
the winter and spring of 1980, 12-
x 15-m plots replicated four times were
treated with 0,11, 22,45,90, or 180 MT/
ha (dry-weight basis) of a lime-
stabilized sludge from a plant where fer-
ric iron is used for phosphorus removal.
Plots were also established to test
sludge from the Zimpro process. These
plots were rotovated and transplanted
with seedlings or transplants of Colo-
rado blue spruce, Douglas fir, Fraser fir.
Scotch pine (Spanish Guararrama), and
eastern white pine. New terminal
growth of all trees was measured in the
summers of 1980 and 1981. Total
heights of all conifers were measured in
1982. In 1980, white pine needles from
one branch of each seedling were com-
bined for each plot and analyzed for var-
ious chemical elements. In 1981, inter-
planted white pines at the well drained
site were harvested in total. Roots were
rated for fine root and mycorrhizal de-
velopment, roots and shoots were dried
and weighed, and needles were ana-
lyzed for various elements. In the sum-
mer of 1980, four 0.5-m2 subplots per
plot were clipped by hand before any
mowing, and weed biomass was deter-
mined. Weeds were separated and
classed by botanical family to deter-
mine whether sludge application in-
creased weed growth or whether it al-
tered weed species composition.
Results
Sludge at various rates slightly im-
proved the growth of all species but
Fraser fir. With the lime-ferric sludge,
growth was greatest at the 11- or 22-ton
application rates, with marked growth
reductions at higher rates. In contrast,
maximum growth on the Zimpro-
sludge-treated plots occurred at the two
highest application rates—45 or 90 MT/
ha. At the well drained site, maximum
survival in the lime-ferric sludge oc-
curred at the 11- and 22-ton rates (sig-
nificant only for white pine). In Zimpro-
sludge-treated plots, no consistent
effect was detected, partly because of
the inclusion of several wet plots with
abnormally low survival rates. On the
poorly drained site, survival was in-
versely proportional to sludge rate in
both the 1980 and 1981 plantings. Fur-
thermore, the approximate degree of
toxicity was the same in both years. The
deleterious effect of sludge on survival
was not transitory (as it might be, for
example, with high initial ammonia ac-
cumulation), but it persisted for a year
at about the same intensity.
The survival of blue spruce, Douglas
fir, Fraser fir, and the pines was influ-
enced by sludge loading rate. At rates in
excess of 45 MT/ha, survival was signif-
icantly poorer after 2 years in the field
than survival at lower loading rates. Al-
though significant differences occurred
in growth among various tree species at
different loading rates, no distinct trend
identified which sludge loading rates
were either the best or the poorest for
tree growth. The sludge loading rate of
Zimpro sludge in 1981 appeared to have
no effect at all on the growth of blue
spruce, Douglas fir, Fraser fir. Scotch
pine, and white pine in the same year of
sludge application or 1 year later. Sur-
vival of these same species was gener-
ally better at the lower sludge loading
rates. But the survival at the end of two
growing seasons was significantly bet-
ter for all species supplemented with
lime-ferric sludge at rates under 45 MT/
ha on the poorly drained site.
Greater growth of interplanted white
pine seedlings in the lime-ferric sludge
occurred on the better-drained soil
where the same sludge loading rates
were applied than on the heavier, more
poorly drained soil.
No differences occurred in the shoot
weights of white pines grown in either
Zimpro or lime-ferric sludges at any of
the loading rates tested, and only slight
differences occurred in root weights of
trees grown on the Zimpro sludge.
Loading rates produced a slight differ-
ence in mycorrhizal incidence in white
pine grown on the lime-ferric sludge,
and they produced more pronounced
differences among those grown on the
Zimpro sludge. Mycorrhizal infection
appeared to be hindered with both
sludges at sludge loading rates above
45 MT/ha.
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Tree Seedling Production in a
Conventional Outdoor Nursery
Procedures
At the Zanesville, Ohio, State Tree
Nursery, eight adjoining 1.2-x90-m
beds of a sandy loam soil were plowed,
disked, and fumigated with methyl bro-
mide/chloropicrin in September 1979. In
October, a poorly digested (primary
treatment only) municipal sludge and
an anaerobically digested liquid sludge
(about 10% solids) were applied at ap-
proximate rates of 35, 80, and 200 MTV
ha (dry-weight basis). A ninth plot was
fertilized with 120 kg/ha of NH4NO3 in
the spring of each year. Ammonium ni-
trate at this rate is normally applied for
seedling production at this nursery, but
it is applied only once, and before
seeding.
In spring 1980, the eight beds were
disked and seeded with northern red
oaks, black locust, yellow poplar,
Douglas fir, noble fir, Colorado blue
spruce, Scotch pine, eastern white pine,
and Virginia pine. These species were
planted in 1.2- x 1.2-m plots replicated
five times at random in each 90-m bed.
In late July, approximately 20 plants
were harvested from each plot. Root
and shoot weights were determined,
and foliar chemical analyses were per-
formed on yellow poplar shoots and
black locust leaves.
In September 1980, the site was again
disked and fumigated to destroy weed
seeds. The beds (previously amended
with sludge) were then disked, divided
into 10 blocks of eleven 0.6- x 1.2-m
plots, and seeded with white oak, red
maple, black locust, sycamore. Scotch
pine, Virginia pine, eastern white pine,
Douglas fir, noble fir, and blue spruce.
Seeds were placed in furrows, covered
with sawdust, and hydromulched. In
1980, white oak, sycamore, yellow
poplar, and black locust were har-
vested, weighed, digested, and ana-
lyzed. During the summer of 1982, the
red maples and Virginia pines were also
harvested, weighed, and analyzed.
Results
In the summer following fall applica-
tion of the sludges at the Zanesville
Nursery, certain sludge rates signifi-
cantly improved the growth of black lo-
cust and yellow poplar seedlings com-
pared with those on the control plot,
which received no nitrogen. Red oak
was not affected, possibly because its
large seed nutrient reserves diminished
the effects of soil nutrients on initial de-
velopment. Coniferous seedlings as a
group responded significantly to inor-
ganic N, but not to sludge. The 80 MT/ha
rate of anaerobically digested sludge re-
duced conifer shoot growth signifi-
cantly, and in some cases, a poorer root
system was evident. The 200-MT appli-
cation rate was abandoned because of
the heavy weed growth derived either
from soil mixed with the sludge, seeds
in the sludge (mostly tomato), or natu-
rally occurring seeds.
Sludge treatments increased the up-
take of phosphorus in some cases, and
generally decreased Mn uptake. Foliar
Zn was higher with the primary sludge
treatments, and Cu was higher in cer-
tain treatments, particularly those with
anaerobically digested sludge. How-
ever, foliar Cr was not significantly
higher in trees from plots treated with
the high-Cr digested sludge.
Adding large quantities of organic
matter by way of sludge appeared to
sequester some of the cations present
in the mix. Elements such as copper
were accumulated at higher concentra-
tions in certain species such as syca-
more, yellow poplar, black locust, and
red maple. Various sludge loading rates
produced small (if any) differences in
the copper concentrations of Virginia
pine and white oak. Sludge loading rate
was not consistently correlated with in-
creased uptake of various elements
over all species. Some selectivity ap-
peared to be expressed among species
for certain elements such as copper,
magnesium, and calcium.
Soil organic matter and water con-
tents increased significantly only with
the highest rate of primary sludge appli-
cation—the same treatment that
improved the growth of several tree
species.
Containerized Tree Seedling
Production
Procedures
This study used a variety of single-cell
containers. The rooting medium was a
1:1 ratio of peat and No. 2 horticultural
vermiculite adjusted to an initial pH of
5.5 with 1 g of hydrated dolomitic lime
per liter of mix. Granules (2 to 9 mm) of
dried, anaerobically digested sewage
sludge were added at rates of 4%
and 3.5% (v/v) in 1980 and 1981,
respectively.
In 1980, containers used were repli-
cated five times. One fourth of each con-
tainer unit was seeded with either white
pine, blue spruce, Douglas fir, or noble
fir and covered with a 1-cm layer of ver-
miculite. The same procedure was fol-
lowed in 1981 for the container types
used, although some different contain-
ers were used.
In 1980, the rooting medium was fer-
tilized twice weekly with a solution con-
taining 150 ppm N, 50 ppm P, 100 ppm
K, 65 ppm Ca, 40 ppm Mg, 50 ppm S,
5 ppm Fe, 0.5 ppm Mn, 0.5 ppm B, 0.05
ppm Zn, and 0.01 ppm Mo (pH 5.7). In
1981, the medium was fertilized once
weekly with half the volume of the
above solution at 2.4 times the previous
strength, and an equivalent amount
was sprayed over the tree foliage once
weekly. Trees were illuminated by two
metal halide lamps that provided an av-
erage supplemental light intensity of
400 lux at the tops of the containers for
24 hours per day in 1980 and 18 hours
per day in 1981. Twenty to 25 of the best
seedlings produced in the first and sec-
ond years were planted in the field for
performance evaluations.
Partially digested sewage sludges
were obtained from Canton, Cleveland,
and Mt. Vernon, Ohio, and from Detroit,
Michigan. Sludges were air-dried, and
small volumes were ground dry in a
Waring* blender. Ground sludges were
screened through sieves to obtain parti-
cles 1 to 3 m in diameter, 3 to 5 mm in
diameter, and 5 to 7 mm in diameter.
Equal volumes of particles within each
size range were mixed together. The pH,
organic matter content, and mineral
composition were determined for each
sludge.
A potting mixture consisted of two
parts soil, two parts sand, and one part
peat moss. Powdered sludges were
added to the soil mix to achieve concen-
trations of 2.4%, 5%, 10%, and 25%
sludge on a v/v basis. Each 600-ml sty-
rofoam container held 575 ml of potting
mix.
Results
Positive responses to sludge were
significant in every growth category for
every species. In comparisons of indi-
vidual container types for 1980, the
smaller sizes were less likely to show
significant sludge-associated responses
than were the larger sizes. This result
may have occurred because growth
was more restricted by space limita-
*Mention of trade names or commercial products
does not constitute endorsement or recommenda-
tion for use.
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tions than by nutrition. Differences in
the growth of the 1980 seedlings per-
sisted after transplanting, with an aver-
age 98% survival rate for Douglas fir,
blue spruce, and white pine seedlings
grown in sludge versus 93% for those
grown without sludge.
Mycorrhizal Relationships
Procedures
Chlamydospores of Glomus fascicu-
latus were obtained from pot cultures of
corn by the process of wet sieving and
decanting. Mixed with the soil in each
pot were 250 spores. The Rhizobiutn
isolate used in this experiment was ob-
tained from nodules collected from
black locust roots. Root nodules were
surface-sterilized and ground for 20 sec;
5 ml of the resulting suspension was
pipetted onto the soil surface of each
pot. Black locust seeds were treated in
concentrated sulfuric acid, rinsed, and
planted in the pots. The resulting seed-
lings were provided a 14-hr day by sup-
plemental light. Day and night tempera-
tures were controlled, and plants were
watered as needed.
Seedling height was measured after
10 weeks. Stems were severed from
roots, both were washed, root nodula-
tion was assessed, and plant parts were
dried and weighed. Roots were strained
and examined microscopically for the
presence of mycorrhizae.
G. fasciculatus spore germination
was assessed before inoculating soils.
In addition, spores were exposed to the
heavy metals Mn, Ni, Cu, and Zn in agar
media. Sludge-amended agar was pre-
pared using an anaerobically digested
sludge.
Mycorrhizal colonization was deter-
mined by fixing root samples in a solu-
tion of ethanol, water, acetic acid, and
formaldehyde. They were boiled in
potassium hydroxide, rinsed, and
stained for microscopic examination.
Results
Non-mycorrhizal seedlings respond
much more positively to sludge than do
mycorrhizal seedlings. The response
difference is primarily due to P nutrition,
and the difference in growth can be
translated into a P stimulus equivalent
of 50 ppm of added P. An activated
sludge such as Milorganite can nearly
eliminate a mycorrhizal response of
soybeans by reducing the availability of
P to the plants. A low recovery of
mycorrhizal activity can be expected
even after a second planting of soy-
beans in the same once-used soil-
sludge mix. Mycorrhizal infection will
decline with increased sludge concen-
trations in a growth medium. Soluble
heavy metals in sludge are generally
detrimental to fungus spore germina-
tion and hyphal development. Soil con-
centrations of available or exchange-
able Zn between 10 and 50 fjg/g will
cause an abrupt decline in Glomus
macrocarpus chlamydospores. Lower
levels of Cu cause variable results, but
amounts as small as 1 |xg of exchange-
able Cu have detrimental effects on
mycorrhizal fungus spore germination.
Copper Requirements of
Conifers
Procedures
A set of three experiments was de-
signed to determine whether Cu was
limiting the growth of containerized
coniferous seedlings. The first experi-
ment used a 1:1 (v/v) peat-vermiculite
(PA/) mix and a 7:3 (v/v) mix of com-
posted hardwood bark and vermiculite
(BA/). The PA/ pH was left at 6.9. Con-
tainers (160-ml tubes) were each filled
with 150 cc of these media and seeded
with blue spruce, Douglas fir, noble fir,
or eastern white pine. After the seed
coats were cast, seedlings were thinned
to one per cell. The PA/ treatments were
fertilized with 150 ppm N, 50 ppm P, 100
ppm K, 65 ppm Ca, 40 ppm Mg, 50 ppm
S, 5 ppm Fe, 0.5 ppm Mn, 0.5 ppm B,
0.05 ppm Zn, and 0.01 ppm Mo. The BA/
treatments were fertilized with 300 ppm
N and other elements at 120% of the
rates used for the PA/ mix. Copper as
CuS04-5H20 was added to the fertilizer
solutions at final concentrations of 0.00,
0.01,0.04,0.16, or 0.64 ppm, resulting in
approximately 0.00,0.05,0.20,0.80, and
3.20 (jig Cu per cc of PA/ mix. In another
treatment, the PA/ and BA/ mixes both
contained 2% (v/v) digested municipal
sewage sludge equivalent to 14 n.g Cu
per cc of container medium. Other ele-
ments added by the sludge were as fol-
lows
N..
P ..
K..
Ca.
Mg
Fe.
Zn.
.552
.670
. 70
.850
.100
. 18
. 17
B
Mo ...
Cr
Pb ..
Cd
Ni
Hq ..
Na . . . .
.... 5
0.5
14
4
. . . . 0.3
7.7
. ... 1.2
... 56
The sludge treatment was not amended
with Cu. Nutrient solutions were ap-
plied directly to the media twice weekly,
and the trees were watered on other
days with deionized water. The P/V
seedlings were measured, harvested,
and weighed after 5 months, and the
B/V seedlings were harvested and
weighed after 6 months.
The second study was conducted
with Douglas fir in the same type of con-
tainer with the same PA/ mix. Before
seeding, the mix was amended with
drenches of CuSO4-5H2O (0, 2,5,10, 20,
50, or 100 mg/L) applied in a 20-ml-per-
tube aliquot.
In the third experiment, Douglas fir
was grown in a randomized 3x3 fac-
toral arrangement of Cu (0, 10, or 100
ppm) and N levels of 25, 100, or 250
ppm in the fertilizer solution.
Results
In many cases (and apparently for
less-than-obvious reasons), tree re-
sponse to sludge is greater than to vari-
ous inorganic fertilizers. This result in-
dicates that the response in such
instances is not due to major nutrients,
since treatments causing less growth of
blue spruce and Douglas fir induced
higher foliar amounts of P, K, Mg, and
Ca. A close relationship exists between
tree growth and Cu availability in soils.
Other metals do not seem to be as criti-
cal to growth. Cu availability is affected
by the sludge pH, which is determined
by the waste treatment process. For ex-
ample, although the same total amount
of Cu might be added through a lime-
ferric sludge, the element is less avail-
able for plant uptake than when it is pre-
sented in an activated sludge with
greater free acidity (lower pH). Copper
deficiencies can be expected to be more
severe in a B/V medium than in a PA/
medium. In fact, mixing fairly large
amounts of sludge with a bark medium
will probably not supply sufficient Cu
even for white pine. Douglas fir is the
one conifer studied that not only re-
sponds well to a single, large applica-
tion of Cu, but also tolerates excessive
Cu loadings.
Conclusions
Some sewage sludges can be used
effectively to fertilize field grown
Christmas trees, but responses vary
with sludge properties and rate of use,
soil properties, and tree species. Appli-
cations of up to 22 MT/ha will usually
furnish needed nutrients without caus-
ing toxicity. Applying 45 MT/ha or more
lowers the survival and growth rate of
pines.
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Field tree nursery seedlings vary in
response to sludge use because of soil
properties, tree species, sludge proper-
ties, and application rate. Black locusts
and yellow poplars were the only hard-
woods to exhibit greater height growth
because of sludge applications. High
application rates impeded shoot devel-
opment of conifers. Surface application
of 85 MT/ha or greater cause intolerable
weed growth unless the soil is fumi-
gated after sludge application.
Adding stabilized sewage sludge to
potting mixture at rates up to about 5%
of the growing medium can stimulate
both height and diameter of conifers
and achieve better survival when they
are transplanted outdoors.
Mycorrhizal tree seedlings respond
less to sludge application than non-
mycorrhizal species. Use of sludge for
growth of containerized seedlings tends
to impede mycorrhizal development ac-
cording to sludge use rate and may
cause seedlings to have a less-than-
optimal number of mycorrhizal infec-
tions for adapting to poor sites at out-
planting time.
The full report was submitted in fulfill-
ment of Grant No. R806672 by The Ohio
State University under the sponsorship
of the U.S. Environmental Protection
Agency.
D. H. Lambert, T. C. Weidensaul, D. C. Borger, and L. H. Rhodes are with Ohio
Agricultural Research and Development Center, Wooster, OH 44691.
G. K. Dotson is the EPA Project Officer (see below).
The complete report, entitled "Use of Sewage Sfudge for Forest-Tree Seedling
Production,"(Order No. PB 85-241 875/AS; Cost: $14.50, subject to change)
will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
For information, contact James Ryan at:
Water Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
•fr U. S. GOVERNMENT PRINTING OFFICE:1985/559-l 11/20708
-------
United States Center for Environmental Research
Environmental Protection Information
Agency Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S2-85/095
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U $ £NVIR ?!2If$TION AGENCY
CHICAGO
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