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 top-quality 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. (perhaps not necessary) 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.(what about the other fifteen worms?) The fifty worms were divided into five
containers, equaling ten worms per container.
In order to produce create (redundant) the mulch bedding for the worms while they were in the
plastic containers, newspaper was shredded into pieces, no more than one inch-thick, 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. (maybe mention this when you mention weighing the first
time) 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 (redundant), 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 (why?). 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. (portray the tables results without explaining it, and table captions go on top of the
table)
We had expected that the Eisenia fetida which (that) 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.
(Discussion)
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 and fertility of soils, 25(1), 20-26.
Gruner, B., & Zebe, E. (1978).
earthworms. Comparative
Biochemistry
Biochemistry, 60(4), 441-445.
Studies on the anaerobic metabolism of
and
Physiology
Part
B:
Comparative
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, and Thomas Welsh
Title: The effect of varied diets on the nitrate concentration of the castings of Eisenia fetida after
vermicomposting
Summary
Eisenia fetida, a common annelid worm, provides many areas of soil with nutrients due to
vermicomposting, basically worm composting. The organic material of the worms decomposes
into the soil. The experiment was an attempt to discover the source of food that will produce the
most nitrate rich worm waste, whether it is green matter, a mixture of blended broccoli stalks and
water, brown matter, a mixture of dead leaves and water, or mulch, the control group. Their
results indicated that the group which consumed green matter produced the highest nitrate
concentration. This finding can be implemented for vermicomposting and for the activity of
microbial bacterial colonies.
General Comments
The experiment is well thought out and the idea is one that can be impactful to modern day
agriculture. Great Job!
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.
.Table headings go above the table
.Consider if a table is absolutely necessary
.Perhaps ditch the columns
.single spacing in the title
This paper was a final version
This paper was a rough draft
Recommendation
should be published as is
☺ This paper should be published with revision