The effect of varied diets on the nitrate concentration of the castings of Eisenia fetida after
vermicomposting
(Suggested Title: The Effect of Varied Diets on the Nitrate Concentration of the Castings
of Eisenia fetida After Vermicomposting)
Samantha Galang, Peter Garcia, Thomas Welsh
Department of Biological Sciences
Saddleback College
Mission Viejo, 92692
Vermicomposting is a commonly practiced form of fertilizing by using worms to recycle
food scraps and other organic materials into a valuable soil product. The nutrients
consumed by Eisenia fetida the ideal species used in vermicomposting, are integrated into
the compost produced by these worms, which is then used as fertilizer. In this experiment,
nitrate concentration was measured after feeding the worms three different diets including
dead leaves, which represented brown matter, broccoli stalks, which represented green
matter, and a no-nutrient diet, which was pure mulch. After one week of feeding the worms
these diets, a nitrate test was conducted to test the nitrate concentration of the castings of
the worms. The result showed that our hypothesis, a diet consisting of brown matter would
produce more nitrates, was, in fact, incorrect, and the diet consisting of green matter
proved to produce more nitrates.
Introduction
Eisenia fetida is a type of annelid presiding
primarily in North America. It commonly
feeds on vegetation in un-tilled areas like
meadows and woods (Boyle, 1997). Their
consistent movement through the soil
provides the soil with nutrients and allows
water and air to get into the soil. E. fetida
can feast on dead leaves, manure, and other
organic matter in the soil in which they live.
Additionally, these “red wigglers” consume
food by pulling leaves into the mouth of its
burrow in order to let the leaves decay
(Gruner, 1978).
Red wigglers’ castings are regarded as a topquality fertilizer because of the lack of
pesticides incorporated into the soil and fed
to the worms. The organic product of these
worms, as a result of worm composting or
vermicomposting, is coveted due to the rich
nutrient content. Earthworm farms are
heavily invested in producing organic
fertilizer through the use of night crawlers.
Materials and Methods
Three containers of both male and female
red wigglers in soil were purchased from
PetSmart in Tustin, CA on April 14th, 2014.
Each container held 50 to 55 worms for a
total of 165 worms. The worms were
divided into three groups with 55 worms per
diet. Fifteen separate plastic containers were
purchased from Smart ‘n’ Final to house the
worms. Holes were created in the lids of the
plastic containers for ventilation purposes.
The different diets for the worms consisted
of green matter, brown matter, and mulch,
which served as the control group. Each diet
would be fed to fifty worms, with a total of
150 worms being tested. The fifty worms
were divided into five containers, equaling
ten worms per container.
In order to produce create the mulch
bedding for the worms while they were in
the plastic containers, newspaper was
shredded into pieces, no more than one inchthick, and dampened with water. The green
matter was produced by blending broccoli
stalks with water to break up the broccoli
into small, moist pieces. The brown matter
was produced by crushing dead leaves and,
once again, dampening with water for a
softer consistency.
Approximately 17.30 g of mulch was placed
into each of the fifteen containers. A group
of ten worms was weighed, and placed into
one container of mulch. This served as the
first control group (Group C1). Four more
groups of ten worms were weighed and
placed into containers, which resulted in the
remainder of the control groups (Groups C2
to C5). Approximately two to three grams of
green matter was placed into five more
containers with mulch. These groups were
titled Group V1 to V5. Approximately three
to four grams of brown matter was placed
into another five containers. Once again, the
mass of each group of ten worms was
obtained before placing them into the
containers. A sample of each diet, mulch +
green matter, mulch + brown matter, just
mulch, were obtained. Once all the
containers of worms were prepared, they
were left indoors to retain constant
temperature.
The castings of each group were obtained
for each group, and placed into their own
centrifuge tubes. For every gram of castings,
5 mL of 1M KCl was dispensed into the
centrifuge tube of castings. The tubes were
shaken at 100 rpm for ninety minutes, then
centrifuged for fifteen minutes at 3200 g.
Afterwards, the sample was decanted into a
10 mL test tube. Each sample was then
tested for nitrates using the LaMotte’s
testing kit. Using the color scale provided by
the nitrate test, each sample was interpreted
in terms of nitrate concentration (ppm).
Results
Using the LaMotte’s Nitrate test kit it was
shown that the level of nitrates was highest
in the green matter, followed by brown
matter, and the control held the least amount
of nitrates.
Diet
Control
Group
Brown
Matter
Green
Matter
Tube 1
0
Tube 2
0
Tube 3
0
Tube 4
0
Tube 5
0
1
1
1
2
1
2
2
2
1
1
Table 1. Comparison between three dietary
groups in parts per million (ppm). Green
matter yielded the most nitrates in the tubes,
while the control group yielded the least
amount of nitrates. La Motte’s Nitrate test
kit was used to make a comparison between
the three dietary groups.
We had expected that the Eisenia fetida
which were fed a diet of brown matter
would have castings that were more nitrate
rich.
We hypothesized this outcome
because the habitat of E. fetida generally
consists of the decaying vegetation which
exists in the upper soil levels (Paradise
2001). The results indicate that the castings
from the E. fetida that were fed the green
matter had a higher nitrate concentration.
We found that the casting in the green
matter had a higher average concentration of
nitrates than the brown matter castings by
0.4 ppm.
E. fetida are commonly used to help
break down dead organic organisms in a
process referred to as Vermicomposting.
The worms help to aerate the substrate and
their castings provide a nutrient rich
fertilizer of sorts. E. fetida are also known
to decrease microbial bacteria populations
while possibly increasing the efficiency of
microbial resource utilization (Scheu 2002).
Vermicomposting is a faster and safer
alternative to regular composting, which can
reach high temperatures. The fact that E.
fetida more efficiently recycles green matter
can allow for more efficient composting
through
the
implementation
of
vermicomposting.
Conversely,
these
findings could be used to try to mitigate
nitrate pollution by decreasing the nitrate
levels in the soil by removing the green
matter from the area. This finding could
also be used to artificially boost population
activity in microbial bacterial colonies.
As a supplement to this experiment it would
be interesting to isolate the species of
microbial bacteria that E. fetida affects, and
test how this species effects the nutrient
concentrations found in the soil.
Literature Cited
Boyle, K. E., Curry, J. P., & Farrell, E. P.
(1997). Influence of earthworms on soil
properties and grass production in reclaimed
cutover peat. Biology
soils. 25(1) : 20-26.
and
fertility
of
Gruner, B., & Zebe, E. (1978). Studies on
the
anaerobic
metabolism
of
earthworms. Comparative Biochemistry and
Physiology
Part
B:
Comparative
Biochemistry. 60(4):441-445.
Paradise, C., 2001, A Standardized Soil
Ecotoxicological Test Using Red Worms
(Eisenia fetida), The American Biology
Teacher. v. 63(9): p. 662-668.
Scheu, S., Schlitt, N., Tiunov, A.,
Newington, J., and Jones, T., 2002, Effects
of
the
Presence
and
Community
Composition
of
Earthworms
on
MicrobialCommunity
Functioning,
Oecologia. v. 133(2): p. 254-260
Review Form
Department of Biological Sciences
Saddleback College, Mission Viejo, CA 92692
Author (s):_
Samantha Galang, Peter Garcia, Thomas Welsh____________________________________
Title: The Effect of Varied Diets on the Nitrate Concentration of the Castings of Eisenia fetida
After Vermicomposting_____________________________________________________
Summary
Summarize the paper succinctly and dispassionately. Do not criticize here, just show that you
understood the paper.
Eisenia fetida is a type of annelid located mainly in North America. It regularly feeds on
vegetation in un-tilled areas like meadows and woods. E. fetida are commonly utilized to assist
in the breaking down of dead organic organisms in a process referred to as Vermicomposting.
Their frequent movement through the soil permits air and water to travel into the soil and offers
the soil with nutrients. The nutrients are then combined into the compost posted by these worms
and then utilized as fertilizers. The experimenters wanted to see the effect of different diets on
the nitrate concentration of the castings of Eisenia fetida (a species of earthworm) after
vermicomposting. They had hypothesized that a diet consisting of brown matter would produce
more nitrates. The diets tested were green matter (broccoli stalks), brown matter ( dead leaves),
and mulch( shredded newspaper) which served as the control group due to it being a no nutrient
diet. After one week of feeding the worms these diets, a nitrate test using the LaMotte’s testing
kit was conducted to test the nitrate concentration of the castings of the worms. The result
showed that their hypothesis was incorrect and that a diet consisting of brown matter does not
produce more nitrates. Instead, the results showed that the diet consisting of green matter
produced more nitrates. These findings could be used to try to mitigate nitrate pollution by
decreasing the nitrate levels in the soil by removing the green matter from the area.
General Comments
Generally explain the paper’s strengths and weaknesses and whether they are serious, or
important to our current state of knowledge.
One of the strengths of the paper was the abstract. The abstract was accurate and
succinct. The abstract also did a good job of explaining the hypothesis and results of the paper.
The problem with the abstract was that there was no statistical data posted on the abstract. An
example was that it stated that green matter produced more nitrates. However, it did not list how
many nitrates were produced or if it was a significant difference. The materials and methods was
another section that showed strength. The authors did a great job with writing in passive voice.
They stated all the methods clearly and concisely and did a superb job naming the species and
giving the sample size. There was a minor problem with the materials and method. The issue was
that it did not list when and where the study took place. The authors also did a great job
explaining Eisenia fetida, an earthworm that is located in North America and feeds on
vegetation. They also did an excellent job explaining the process of vermicomposting.
The biggest weakness of the paper was that it did not have a discussions section. It is very
important to have the discussions section because that’s where the conclusion for the results is
supposed to be located. The authors wrote a brief conclusion about the results, but they did not
have it in the write section. Another issue with the paper was that it did not have an
acknowledgement section. Acknowledgement section is needed in order to give credit for those
who helped with the success of the project. There were frequent issues with the formatting of the
paper. Authors failed to indent beginning of paragraphs and headings were not in bold. There
were also issues with the citations utilized in the paper. The issues included forgetting to use a
comma between the last name of author and the date, not including all authors’ names in the
citation, and incorrect formatting of literature citations. In addition, the authors did not have 10
references cited. There were also issues with the results of the assignment. There was no
statistical analysis and no figure graph. The table listed on the research paper looked
unprofessional and lacked axis titles. The caption should have been above the table not below.
The study itself was interesting and it was exciting to learn that diet consisting of green
matter produced more nitrates. This is important to our current state of knowledge because these
findings could be utilized to attempt to mitigate nitrate pollution by lessening the nitrate levels in
the soil by eliminating the green matter from the region. It also can be utilized to artificially
increase population activity in microbial bacterial colonies.
Technical Criticism
Review technical issues, organization and clarity. Provide a table of typographical errors,
grammatical errors, and minor textual problems. It's not the reviewer's job to copy Edit the
paper, mark the manuscript.
This paper was a final version
This paper was a rough draft
There is a high amount of grammatical and typographical errors. Examples include:
The word “Eisenia fetida” should be italicized. In the abstract it is not italicized.
In the title, the location should be “Mission Viejo, CA 92692” not “Mission Viejo, 92692.”
First line of paragraphs was not indented.
Headings were not bold.
Introduction was short and should be longer.
The citation should have all the referenced authors’ names. For example the authors wrote
“(Boyle, 1997)” when it should be “(Boyle, Curry, and Farrell, 1997)”. Authors wrote “(Scheu,
2002)” when it should be “(Scheu, Schlitt, and Tiunov, 2002)”. Not only did author not put every
authors name but they also forgot a comma between last name and date.
List both authors names referenced in citation. Authors wrote “(Gruner, 1978)”. In this case it
should be “(Gruner and Zebe, 1978)”.
The phrase “each group” was used twice in the same sentence and it sounded repetitive. “The
castings of each group were obtained for each group”
There are words with the same definition being used right next to each other. “In order to
produce create the mulch bedding for the worms while they were in the plastic containers”
Table captions should go on top of the table. The author has it below the table.
There is no discussion section on this paper.
There is no acknowledgement section on this paper.
There should be 10 references in the literature cited. Paper only has 4 references.
Literature cited has incorrect formatting. Examples include:
Paradise, C., 2001, A Standardized Soil Ecotoxicological Test Using Red Worms (Eisenia
fetida), The American Biology Teacher. v. 63(9): p. 662-668.
Scheu, S., Schlitt, N., Tiunov, A., Newington, J., and Jones, T., 2002, Effects of the Presence and
Community Composition of Earthworms on MicrobialCommunity Functioning, Oecologia. v.
133(2): p. 254-260
Recommendation
 This paper should be published as is
 This paper should be published with revision
 This paper should not be published