OFFICE OF SOLID WASTE

                        OCTOBER 1999


This report was funded by the Office of Solid Waste, United States Environmental Protection
Agency and the Forest Service, United States Department of Agriculture.  Nothing in this report
constitutes a regulatory action on the part of either agency.  Any reference to companies or
products in this report does not constitute an endorsement of them by the United States
Environmental Protection Agency and the Forest Service, United States Department of


This proj ect was a demonstration of the effects of compost on the growth of hardwood and softwood
tree seedlings. There is interest in identifying cost-effective means to improve the revegetation of
severely disturbed sites. The standard method of revegetating these types of sites generally involves
seeding and/or planting, fertilizing, and mulching. For erosion control and revegetation, grass seed,
pine seedlings, chemical fertilizers, straw and machine-blown pulp mulches are commonly used.

This report was a cooperative effort by the U.S. Forest Service, U.S. Department of Interior Bureau
of Indian Affairs' Cherokee Forest Branch and the Office of Solid Waste, Environmental Protection
Agency (EPA). Two mountainous sites were used on the Cheoah Ranger District of the Nantahala
National Forest and one in the adjoining Qualla Cherokee Reservation in western North Carolina
with permission of the Cherokee Tribal Council. Joseph D. Bonnette, Silviculturist, Cheoh Ranger
District, National Forests inNorth Carolina, Robbinsville, N.C.; Dr. Rosalie Green, Senior Recycling
Specialist,  (NCBA  grant participant); and Terry Grist of the USEPA Office  of Solid Waste
conducted this study. This effort was funded under an Interagency Agreement #DW12936577-01-0.

Study Design

This study tested the hypothesis that the use of composted products  from  organic materials has
practical uses in forestry related applications and has the potential to  improve the growth of tree
seedlings in severely degraded soils. During December 1994, a group of tests were initiated on three
damaged (e.g. compacted or severely eroded)  sites to compare a  standard  straw mulch  to three
different composts  used as mulches (biosolids, yard and MSW).  Although pines have been
developed for consistent characteristics, both softwood and hardwood seedlings were used to provide
a greater variety of tree seedling responses. White pine, chestnut oak and Chinese chestnut seedlings
were planted. The conifer seedlings were 8-10 inches high and the hardwood seedlings were 24-30
inches high in 1994. Seedling growth and response of natural revegetation  were monitored from
December 1994 to the summer of 1998. Comparisons of ground cover, soil erosion, growth and
survival data, and soil nutrient values showed distinct differences in the four treatments.

Mulch materials were generally applied 2-inches thick.  Yard compost  was shredded leaves, grass,
tree trimmings, etc. donated from Compost Central of Charlotte, N.C. The commercial cost in 1994
was $10/cu.yd. Biosolids compost was wastewater sludge donated from the City of Lexington, N.C.
The commercial cost in 1994 was $21/cu.yd. Municipal  solid waste compost (MSW) was mixed
municipal solid waste donated from Bedminster Corporation of Sevierville, TN. The commercial
cost in 1994 was $10/ton or $5/cu.yd.  Straw was standard baled straw from Robbinsville, N.C. with
a cost of $4/bale, which equates to roughly $12/cu.yd.

 Description of Test Plots

 Cheogh Clearcut Site #1

A yellow pine/upland hardwood site had been clearcut by the sale to a commercial timber company.
 All residual vegetation was cut near ground level by hand with chainsaws following the logging.
 The logging slash and debris were pushed off the test site with a bulldozer. Most of the topsoil and
 some of the organic duff (i.e., partially decomposed twigs, leaves, etc.) were retained. The ridgetop
 site had eight test plots 12 feet wide by 32 feet long on the southeast face, and eight identical plots
 on the northwest face. The 50 Year Site Index (i.e., the average height growth of trees in 50 years
 of a site ) was 75 feet for shortleaf pine and 68 feet for upland  oaks.  Slopes averaged 30 to 35%.
 Soil samples were taken at 4-5 inches depth prior to the test applications for nutrient assessment.
 All four mulching materials were used as a 2-inch mulch on the sixteen test plots. Thirty white pine
 seedlings were planted in four tests with different mulches on each side of the ridge making a total
 of eight plots. Each of the 480 seedlings were planted in holes approximately 6.0 inches in diameter
 and 12.0 inches  deep made by a hand-held power auger. Each tree was marked with a color-coded
 wire flag ( Figure 1).

 Cheogh Landing Site #2

 The second test site was a log landing devoid of all topsoil and the remaining soil compacted by the
 trucks and tractors used in previous log harvesting.  Site #2 was located on top of a ridge about a
 mile north of ridge #1 and was surrounded by a yellow pine/upland hardwood stand on an old road
 where logs had been loaded on trucks ( Figure 2).  On all eight plots, two inches of mulching
 materials were turned into the hard packed soil by use of a disk harrow pulled by a farm  tractor.
 Additionally, on four test plots, a 2-inch surface mulch was applied.  Chinese chestnut seedlings
 were planted into 12-inch holes made by a 6-inch gas powered auger bit in each of the eight 30 tree
 seedling test plots. Each of the 240 seedlings were marked with a color-coded wire flag.

 Cherokee Old Field Site #3

 The third test site was located within the Cherokee Reservation on a rocky north slope that had a
 marked loss of top  soil. At the bottom of the slope was a small stream. In an old field cleared  of
 brush, Chinese chestnut seedlings were planted into 12-inch holes made by a 6-inch gas powered
 auger bit. The four test materials were added as a 2-inch layer to each  test plot and turned into the
 soil with a disk harrow pulled by a farm tractor. An additional two inch layer of mulch was added
 to each of the plots. More intensive data was collected on sites #1  and #2 because site #3 was
 compromised when a third 1-inch layer of MSW compost was inadvertently spread over the entire
 test sites including the  control  site.  Although site #3  could  not be used  for  valid  statistical
 comparisons, it was quite impressive to observe the average of about 3 feet of growth per year in
 those seedlings that received both turned under and surface applied compost, about 3-inches total
 around each tree.

Figure 1. Cheogh Clearcut site #1. December 1994.
Figure 2. Cheogh landing site #2. December 1994.

             Figures  3  Comparison of the effects of composts  and straw treatments '

            on growth at the Cheogh clearing,  Site # 1.              f       .
  Figure 3a  Three year
               height growth of white  pine and chestnut oak seedlings
              Straw.- 'Yard   Bio   MS W   Straw   Yard 'Bio
                                                                              \Vhite Pine
                                                                              I Chestnut
 Figure 3b Three  year diameter
                       growth of white pine  and chestnut oak seedlings
1   w
                                                                                    White Pjne
                                                                                   Chestnut Oak

 Figures  4   Comparison of the effects of composts and straw treatments

on growth at the Cheogh log landing, Site # 2.
   ..?.i.9Hre  4a- Three year height growth of  Chinese  chestnut  seedlings

                 Bio    Yard    Straw    MSW
   Figure 4b 'Three year diameter growth of Chinese chestnut seedlings

A) Tree Growth-Site #1 and Site #2

White pine: Height growth and diameter growth values after three years for all of the composted
materials were significantly higher than the values for straw, with the highest in the yard compost.
Chestnut oak:  height growth and diameter growth after three years was significantly higher in all
of the compost plots compared to the straw plots ( Figure 3 ) with the highest in the MSW compost.
At the log landing, the height and diameter of the Chinese chestnut tree seedlings was significantly
greater in the MSW compost plot ( Figure 4 ).

B) Survival-Site #1 and Site #2

The survival rates after three years  of growth exhibited certain mixed results. There was a good
survival rate for tree seedlings after planting, regardless of treatment. Among white pine seedlings,
the 3 types of compost treated plots averaged 93% survival and the straw treated plots averaged 92%.
All of the hardwood seedlings survived the first year very well but declined rapidly in the second and
third years. However, this survival pattern is typical of most hardwood species.  The survival rates
of hardwoods among the composts averaged 69% and the survival rate in the straw plots were 77%.
The survival rates of the Chinese chestnut seedlings were impeded by chestnut blight infection and
the damage due to a tree fall across the yard compost plots. Even with  the disease and physical
damage, the survival in the straw plots and in the compost plots both averaged 63%. Among the
three composts, the highest rate of Chinese chestnut survival was 75% in the biosolids compost plots
and the lowest was in the yard compost plots due to damage by the wind-thrown tree. Before the
storm damage, the straw plots showed the lowest survival.

C) Herbaceous Ground Cover—Site#l and Site#2

Herbaceous cover was estimated by the percent of  ground surface area covered for each plot six
months after the initial planting. The average cover for each type of mulch was: biosolids compost
at 95%, yard compost at 80%, MSW compost at 60%, straw at 50%, and an untreated control on
Site#l  at 45%. The natural  revegetation  by  herbaceous plants on the biosolids compost was
remarkable in the first growing season with many plants well over five feet in height. The negative
height growth of tree seedlings in the biosolids plot in Site#l measured after the first growing season
could have been due to that dense herbaceous cover shading the seedlings (Figure 5 ). In all of the
composted plots, the vegetation showed a deeper green color with few yellow hues compared to the
straw plots ( Figure 6 and 7 ).  There was no visible soil erosion in any of the compost or straw plots
during the first year after planting.  However,  erosion was  apparent during the first year in the
untreated areas. In the second and third years,  similar trends were noted except that erosion was
visible in the straw plots as well as the untreated areas. None of the three compost plots showed any
signs of erosion over the three years of observation.  Serially dated  photographs of each test site
showed heavier vegetation cover on all of the compost sites compared to the straw plots.

 D) Soil Nutrient Values-Site#l and Site#2

Soil samples were taken from the center of each of the 24 treated plots in November 1996, nearly
two years after the tests were initiated. Control samples were taken at Sites #1  and #2 from an
adjacent area within 12 feet of the test plots that were site-prepared, but not treated with compost or
straw. Organic component (HM%): The soil organic component (mean values) in the straw treated
plots was 63% greater than the untreated control but 140% greater than the untreated control in the
compost treated plots. In Site#l the MSW compost showed the highest values, and in  Site#2 the
yard compost showed the highest values. In damaged mountain ridges variations in soils could occur
within the 1200 square feet test area.

Soil pH: For the control samples, the mean soil pH was 4.65; for the straw plots the mean pH was
4.75; and for the composts, the mean soil pH was 5.1.  The greatest gains in soil pH were in Site#2
where the compost was plowed into the soil and additional compost was surface-applied. On Site#2,
the straw plot pH was 4.9; the untreated control was 4.7; and the composts averaged a pH of 5.5.
A soil pH of 5.5 is considered to be the minimum desirable level  for growing hardwood trees on
these areas, indicating that soil pH was borderline for compost treated chestnut oak and Chinese
chestnut in these mountainous soils.

Soil nutrient values: Phosphorus (P) was not detectable in any of the control samples or in any of
the samples taken from the straw treated plots. The phosphorus mean values for all of the compost
treated plots was 23.1, and the highest levels in this group  were in the biosolids compost treated
plots.  The potassium (K) and calcium (Ca) values for the control and straw samples were virtually
the same for all areas and the mean values for the compost treated  plots were approximately twice
as high as the control or straw plots. The secondary and micro-nutrient values for magnesium (Mg),
manganese (Mn) , zinc (Zn) and copper (Cu) were significantly higher in the compost treated plots.
The greatest difference of all the nutrients was in the Zn values where the compost samples showed
more than nine times the values  of the control  and straw  plots. The sulfur (S) showed little
differences. It is important to note that the levels of most of the nutrients found in all soil samples
were described by the soil scientists as  below the desirable levels for nursery and  field tree crops.
The low P values were labeled as the most critical. None of the nutrient values in any of the plots
were raised to the highest acceptable values (see Table 1).

Figure 5. Cherokee Reservation hillside, site #3. Chinese chestnut tree seedlings' growth appeared
to be inhibited by 4-5 foot high herbaceous over-shading in the turned-under biosolids compost plot
inadvertently followed by MSW compost mulch

Figure 6. White pine treated with compost mulch (on left) and white pine treated with straw mulch
(on right) seen in site #1.

                TABLE 1. The Nutrient Values of Soil*
 * North Carolina Agronomic Division reported as a standardized index or percentage of the cation
exchange capacity (CEC).

E) Cherokee Site #3

Each of these plots inadvertently received additional MSW compost over most of the area plots when
a severe storm washed the original 2-inch layer of compost downhill in a few areas. This wash down
may have been attributable to the fact that the compost was newly applied and had been screened to
1/4 inch or less rather than the conventional /^ - 3/4 inch screening size. Although the additional
unplanned mulching eliminated the Site #3 data from any valid data comparisons, the results were
unexpectedly significant. The median height growth of all of the surviving seedlings after 22 months
was 48.1 inches.  The average diameter of all the seedlings was 0.81 inches. The overall survival
rate was over 76%.  The growth in Site #3 was much greater than in either of the other test sites.
Height and diameter growth in this plot was greatest in the plot originally turned under and surface-
mulched with yard compost (  Figures 8 and 9  ).  The average tree in the yard compost plot was
slightly over 100 inches in height and was 0.89 inches in diameter: however, some measured over
180 inches in height and about 1.4 inches in diameter. The height growth across all of the compost
test plots was slightly greater than the test plot originally treated with straw only, but inadvertently
"treated" with a 2 inch layer of MSW compost over the straw. These trees appeared to be sustaining
their exceptional growth through the end of the third year, including an average height of 15 feet in
the yard compost plot. In the biosolids test plot (Figure 10), herbaceous volunteer growth continued
to  be robust after three years, compared to the control and straw treated plots, which is consistent
with the use of biosolids compost to establish permanent turf.


Natural revegetation and soil stabilization response were visibly superior in the compost treated sites.
Compost treated test plots had much more visible natural revegetation response and clearly had no
soil erosion and higher soil nutrient values in each of the following three and a half  years after
treatment. During the first year after treatment, the biosolid compost plot showed the highest density
of natural revegetation of grasses and leafy plants and provided the best protection against soil
erosion.  After almost four years, all of the compost treatments were shown to be revegetated to a
much greater degree than the straw treatments. Soil erosion was non-detectable in all of the compost
plots in Sites #1 and #2.  Minor soil erosion was visible in the 2-inch straw treated plots and
vegetation recovery was slower and less dense. Soil nutrient values and pH had recovered far better
in the  compost treated plots compared to the untreated control and straw treated plots.  The
hardwood seedling tests showed mixed results between the treatments early in the test period, but
most of the compost plots resulted in better growth and higher survival rates throughout the three
year test  period. All tree seedlings clearly grew larger in height and diameter in the compost plots
than in the straw. Survival of pine seedlings was also greater in each of the composted plots than
in the straw plots.

The results of this project after three and a half years of monitoring show that compost mulching is
consistently superior to straw mulching for revegetating severely disturbed sites.  Furthermore,
results of the combination of disked under compost plus  compost mulching showed both superior
survival and growth potential of hardwood and softwood tree seedlings even in soil of borderline
nutrient value.  In this particular study, the height and diameter growth of white pine trees was
greatest in plots treated with yard compost, while the height and diameter of chestnut oak trees was
greatest in plots treated with MSW compost.  Forestry application benefits were:  gained soil
rehabilitation, growth of planted seedlings, natural revegetation and in the prevention of soil erosion.

The data produced by this three-year demonstration show that the application of mature composts
contributed to a significant accelerated growth of hardwood and softwood tree seedlings when
compared with straw and no treatment. The enhanced growth by all three composts could have
positive economic implications for public and private tree growers, the lumber industry, the furniture
and building construction industries, the biomass/utility/energy industries and the environmental
entities dealing with clean air and global warming even though the initial costs of using compost may
be greater than straw.

The reproducibility of this study, however, remains to be tested due to the  nature of types of
composts used in the study. First of all, the mature yard compost used was kept thermophilic (120-
140 degrees F) for about five months instead of the usual 3-8 days.  This process is standard for the
company making this compost and was not done solely for the purpose of this study. In addition,
the mature MSW compost used was made from mixed municipal solid waste from residential and

FigureS. Cherokee Reservation hillside, site #3, October 1996. Two-year growth of chines chestnut
tree seedlings, after turned-under yard compost followed inadvertently my MSW compost mulch in

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Figure 9. Cherokee Reservation hillside, site #3, October 1998.  Three -year growth of Chinese

chestnut seedlings, after turned-under yard compost, followed inadvertently by MSW compost mulch

in 1994.


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 Figure 10. Cherokee Reservation hillside, site #3, October 1998. In the biosolids test plot, herbaceous

 volunteer growth at 4-5 feet high, was extravagant after three years.

commercial generators (i.e; compost made from municipal solid waste that has not had recyclables
removed). This means that the MSW compost contained a diversity of organic materials such as
food scraps, paper, and other organics.  These feedstocks are not usually found in combination in
most commercial MSW composts currently being made.  It is uncertain what beneficial effects, if
any, these factors may have had on the quality and composition of the composts.  In addition, the
composts  used in  this study were analyzed by three laboratories for different compositional
characteristics, making comparative analyses of results impractical.

In this study, all three composts ( yard, MSW, and biosolids ) had a 2% nitrogen (N) level which is
more than twice what is generally found in most commercial yard waste composts. We recommend
that future demonstrations compare these composts to those more commonly found  in  the
marketplace.  Additionally, future studies should consider substituting a commercially valuable
hardwood, such as white oak, for the chestnut oak; and that a commercial variety of fruit or nut tree
be substituted for the Chinese chestnut.  All tree seedling planting  and measurements  should
continue to be under the supervision of experienced forest service personnel. Compost analyses
should be done by a single laboratory and that the laboratory meet the standards defined by the U.S.
Composting Council.