Silt vs. loam in Ocimum basilicum L. growth
Daniel H. Snyder, Undergraduate,
Biology, Tennessee Technological University,
Cookeville, Tennessee
December 2, 2009
SILT VS. LOAM IN OCIMUM BASILICUM L. GROWTH
DANIEL H. SNYDER,
Undergraduate Biology, Tennessee Technological University, Cookeville, Tennessee 38505
Abstract: Silt is a granular soil with relatively low water drainage. Loam is gritty and
provides a medium amount of water drainage. Both soil types are very fertile and some
plants show preference toward a certain soil type. The purpose of this research is to
determine which soil type (silt or loam) is more conducive to Ocimum basilicum L. (sweet
basil) growth. The hypothesis is that the plants grown in loam will be larger than those
grown in silt. The null hypothesis is that there is no difference in productivity between the
two treatments. The research showed that loam is the more productive soil type for sweet
basil plants. Plants grown in loam were larger in both mass and size throughout the
experiment and post-harvest. This finding provides sufficient evidence to reject the null
hypothesis in favor of the alternative hypothesis.
Keywords: sweet basil, Ocimum basilicum, nutrient, growth, survival, stress tolerance,
stability, roots, size, water, storage
Introduction
Ocimum basilicum, commonly known as sweet basil, is a pungent perennial herb belonging
to the family Lamiaccae. Basil is native to India, Iran, and tropical regions of Asia (Nazim,
2009). There are between fifty and one-hundred and fifty different species of Ocimum
(Simon, 1999). Basil was shown to produce a high number of viable seeds in the sandy soil
of Pakistan (Nazim, 2009), which shows that basil is capable of growing in a variety of soil
types, and may show preference toward a specific type. Ocimum basilicum is commonly
cultivated for its essential oils, which are used in both the fragrance and pharmaceutical
industries (Shatar, 2007). Water stress, a period of decreased water supply, has been
shown to cause an increase in this essential oil production. In addition, minor water stress
caused an increase in plant growth (Khalid, 2006). Recently, there has been a particular
surge in interest of basil’s essential oils because they have been demonstrated to be useful
in pest control (Regnault-Roger, 1997), as an immunostimulant (Logambal, 2000), as both
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a hypoglycemic and a hypolipidemic agent, as a strong antioxidant (Halim, 2001), and as an
antimicrobial against Giardia lamblia (Almeida, 2007).
Although Ocimum basilicum is medicinally, economically, culinarily, and ecologically
important, there have been few studies to determine the ideal soil type for growing this
herb. This research focuses on two specific types of soil: silt and loam. Silt is a granular
soil that provides relatively low water drainage. Excess water can accumulate around the
roots of a plant and may lead to fungi growth and/or root -rot. In contrast, loam is gritty
and provides a medium amount of water drainage. Both soil types are very fertile and
some plants show preference toward a certain soil type.
The purpose of this research is to determine which soil type (silt or loam) is more
conducive to sweet basil growth. The hypothesis is that the plants grown in loam will be
larger than those grown in silt. Loam seems to provide an ideal level of water
retention/drainage for plant growth. Silt may tend to accumulate too much water which
could affect plant growth by promoting fungi and/or root-rot which would be detrimental
to the plant. The null hypothesis is that there is no difference in productivity between the
two treatments.
Methods and Materials
Sweet basil (Ocimum basilicum L.) plants were studied in this research. These were grown
using a combination of the methods of Nazim (2009) and Khalid (2006). However, all
plants used in this study were grown indoors rather than transplanting them outside. They
were grown under a high-intensity fluorescent lamp (Khalid, 2006).
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Data was collected both while the plants are growing and after harvesting the sweet basil
plants. The data was recorded in the data forms shown below (Tables 1,2).
Table 1. Weekly data collection form
Loam Silt
Length (cm)
Length (cm)
Height (cm)
Height (cm)
Width (cm)
Width (cm)
Week
Number of
Number of
Avg. Plant
Avg. Plant
Avg. Leaf
Avg. Leaf
Avg. Leaf
Avg. Leaf
Leaves
Leaves
1a
2a
3a
4a
1b
2b
3b
4b
Table 2. Post-harvest data collection form
Total Plant
Avg. Plant
Avg. Stem
Avg. Stem
Avg. Leaf
Soil Type
Mass (g)
Mass (g)
Mass (g)
Mass (g)
Length
(cm)
Loam
Silt
All research was conducted in an apartment in Cookeville, Tennessee. The Ocimum
basilicum plants were grown in a temperature controlled environment under a high-
intensity fluorescent lamp. Equipment needed included a growing lamp, growing cups, a
storage tray, a ruler (in centimeters), and a scale (in grams).
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The collected data was analyzed primarily in a quantitative manner. Average plant height
was graphed to enable easier visualization of plant growth for the two treatments. The
data was also statistically evaluated using a t-Test (Gosset, 1908) to test the validity of the
null hypothesis, and with a p-value (Pearson, 1914) to check for validity.
Ocimum basilicum was grown in both loam and silt. Five sweet basil plants were grown in
each soil treatment (Nazim, 2009). The plants received ten hours of fluorescent lighting
each day (Khalid, 2006) and were stored in a dark room when they were not under the
growing lamp. The plants were watered biweekly on Tuesday and Friday. The plants were
observed on Sunday of each week. Weekly measurement data was collected at that time.
The plants were grown for four weeks, then the entire process was repeated for four more
weeks to verify results (Tables 3,4).
Table 3. Scientific Method Matrix
Question
Does sweet basil grow better in loam or silt?
Problem Loam provides ideal water drainage; silt holds
excess water.
Hypothesis/Null-Hypothesis Hypothesis: Sweet basil plants grown in loam will
be larger than the plants grown in silt.
Null: There will be no difference in size between
sweet basil plants grown loam and those grown in
silt.
Objective Statement The purpose of this experiment is to determine
whether sweet basil plants grow more efficiently
in loam or silt.
Experimental Design See TABLE 4
Data Collecting and Processing Observe and measure leaf size and plant size of
plants grown in silt [test] and loam [control]
Conclusions Plants grown in loam were larger than plants
grown in silt.
Communications Present results in a formal platform presentation,
manuscript, and on a website.
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Table 4. Experimental Design for Plant Growth Comparisons (Nazim, 2009; Khalid, 2006)
Treatment Five sweet basil plants are grown in silt and
5 Plants watered biweekly.
Group A
Control Five sweet basil plants are grown in loam and
5 Plants watered biweekly.
Treatment Five sweet basil plants are grown in silt and
Group B
5 plants watered biweekly.
(experiment
Control Five sweet basil plants are grown in loam and
replication)
5 plants watered biweekly.
Results
Loam was shown to be more favorable than silt for Ocimum basilicum growth. This was
evident in both repetitions of the procedure, as loam plants were significantly larger in
mass, length, and leaf production (Tables 5,6).
Table 5. Weekly data for plants grown in loam and silt for weeks 1a-4a (first trial)
and 1b-4b (second trial)
Loam Silt
Length (cm)
Length (cm)
Height (cm)
Height (cm)
Width (cm)
Width (cm)
Week
Number of
Number of
Avg. Plant
Avg. Plant
Avg. Leaf
Avg. Leaf
Avg. Leaf
Avg. Leaf
Leaves
Leaves
1a 0.1 0 0 0 0 0 0 0
2a 0.8 0 0 0 0.3 0 0 0
3a 1.6 3 0.1 0.2 0.8 2 0.1 0.2
4a 3.9 9 0.8 1.1 2.9 6 0.5 0.7
1b 0.1 0 0 0 0.1 0 0 0
2b 0.7 0 0 0 0.4 0 0 0
3b 1.9 4 0.2 0.4 0.7 2 0.1 0.2
4b 3.5 8 0.7 1.2 3.0 7 0.5 0.6
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Table 6. Post-harvest plant data for plants grown in loam and silt for trial two
Total Plant
Avg. Plant
Avg. Stem
Avg. Stem
Avg. Leaf
Soil Type
Mass (g)
Mass (g)
Mass (g)
Mass (g)
Length
(cm)
Loam 5.5 1.1 0.2 0.9 4.1
Silt 4.9 0.98 0.2 0.8 3.1
The data for average plant height for trial one was placed into a line chart to enable easier
visualization of plant growth (Figure 1).
4.5
Average Plant Height (cm)
4
3.5
3
2.5
2 Loam
1.5
Silt
1
0.5
0
1 2 3 4
Week
Figure 1. Line chart comparing average plant height each week
for loam vs. silt
A t-Test (Gosset, 1908) comparing the average plant heights for each treatment gave a T-
statistic of 49.194 and a t-value of 1.729. A p-value (Pearson, 1914) was calculated and
was determined to be 8.453 x 10-22.
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Discussion
As was expected, the sweet basil plants that were grown in loam were larger than the
plants that were grown in silt. This was true for plant height, leaf number, leaf width, and
leaf length throughout the growth stage, as well as the total plant mass, average plant mass,
average stem mass, average leaf mass, and average stem length that was determined after
harvesting. This was likely because loam provides an ideal level of water drainage and the
presence of “stale” water around the roots of plants that were grown in silt significantly
stunted the growth of the basil plants. This result was consistent with the finding that mild
water stress causes an increase in plant growth (Khalid, 2006). The Ocimum basilicum
plants that retained less water were more productive. This was also consistent with the
finding that basil prefers a soil type with higher water drainage (Nazim, 2009). The excess
water may have also caused root-rot and/or fungi to develop around the roots, although
neither was apparent after this short trial.
The results of the t-Test (T-stat=49.194, t-value=1.729, p-value=8.453 x 10-22) provide
evidence to reject the null hypothesis that soil type has no effect on Ocimum basilicum
growth in favor of the alternative hypothesis that sweet basil plants grown in loam will be
larger than those grown in silt. This is possible because t
made with 99% accuracy because p<0.01.
Since sweet basil has been shown to be useful in pest control (Regnault-Roger, 1997), as an
immunostimulant (Logambal, 2000), as both a hypoglycemic and a hypolipidemic agent, as
a strong antioxidant (Halim, 2001), and as an antimicrobial against Giardia lamblia
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(Almeida, 2007), the results of this study should enable this important herb to be cultivated
more efficiently because it shows preference to a specific soil type.
Further research should focus on a larger variety of soil types in order to determine exactly
which soil type is most conducive to sweet basil growth. Also, it would be useful to carry
out this same experiment over a longer coarse of time to determine whether the plants
grown in silt will eventually catch up to the plants grown in loam.
Conclusions
Ocimum basilicum L. does show preference toward a specific soil type.
Loam is a better medium for sweet basil growth than silt.
The null hypothesis was rejected in favor of the alternative hypothesis.
o Sweet basil growth does depend on soil type.
Sweet basil grown in loam were larger (in mass and size) than sweet basil grown in
silt.
Acknowledgements
Dr. Eric Morgan (Biology Professor, Tennessee Technological University), for
guidance throughout the research process.
Sarah Dalton (Undergraduate Student, Tennessee Technological University), for
watering and assisting with plant measurements.
Randy Snyder (father), for gardening advice.
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Literature Cited
Almeida, I., D. S. Alviano, D. P. Vieira, P. B. Alves, A. F. Blank, A. Hampshire, C. S. Lopes, C. S. Alviano,
M. Socorro, S. Rosa. 2007. Antigiardial activity of Ocimum basilicum essential oil. Parasitol Res
101:443-452.
Halim, E., M. A. Hussain, K. Jamil, and M. Rao. 2001. Hypoglycaemic, hypolipidemic, and antioxidant
properties of Tulsi (Ocimum sanctum L.) on streptozotocin induced diabetes in rats. Indian Journal
of Clinical Biochemistry 16:190-194.
Khalid, K. A. 2006. Influence of water stress on growth, essential oil, and chemical composition of
herbs (Ocimum sp.). Internation Agrophysics 20: 289-296.
Logambal, S. M., S. Venkatalakshmi, R. D. Michael. 2000. Immunostimulatory effect of leaf extract of
Ocimum sanctum in Oreochromis mossambicus (Peters). Hydrobiologia 430:113-120.
Nazim, K., M. Ahmed, and M. Uzair. 2009. Growth potential of two species of basil in sandy soil of
Karachi. Pakistan Journal of Botany 41:1637-1644.
Regnault-Roger, C. 1997. The potential of botanical essential oils for insect pest control. Integrated
Pest Management Reviews 2:25-34.
Shatar, S., Sh. Altantsetseg, I. Sarnai, D. Zoljargal, T. D. Thang, and N. X. Dung. 2007. Chemical
composition of the essential oil of Ocimum basilicum cultivated in Mongolian Desert-Gobi. Khimiya
Prirodnykh Soedinenii 6:603-604.
Simon, J. E., M. R. Morales, W. B. Phippen, R. F. Vieira, and Z. Hao. 1999. Basil: A Source of Aroma
Compounds and a Popular and Ornamental Herb. ASHS Press 499-505.
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Appendix
Table A. Scientific Method Matrix
Question
Does sweet basil grow better in loam or silt?
Problem Loam provides ideal water drainage; silt holds
excess water.
Hypothesis/Null-Hypothesis Hypothesis: Sweet basil plants grown in loam will
be larger than the plants grown in silt.
Null: There will be no difference in size between
sweet basil plants grown loam and those grown in
silt.
Objective Statement The purpose of this experiment is to determine
whether sweet basil plants grow more efficiently
in loam or silt.
Experimental Design See TABLE 4
Data Collecting and Processing Observe and measure leaf size and plant size of
plants grown in silt [test] and loam [control]
Conclusions Plants grown in loam were larger than plants
grown in silt.
Communications Present results in a formal platform presentation,
manuscript, and on a website.
Table B. Experimental Design for Plant Growth Comparisons (Nazim, 2009; Khalid, 2006)
Treatment Five sweet basil plants are grown in silt and
5 Plants watered biweekly.
Group A
Control Five sweet basil plants are grown in loam and
5 Plants watered biweekly.
Treatment Five sweet basil plants are grown in silt and
Group B
5 plants watered biweekly.
(experiment
Control Five sweet basil plants are grown in loam and
replication)
5 plants watered biweekly.
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Table C. Weekly data for plants grown in loam and silt for weeks 1a-4a (first trial)
and 1b-4b (second trial)
Loam Silt
Length (cm)
Length (cm)
Height (cm)
Height (cm)
Width (cm)
Width (cm)
Week
Number of
Number of
Avg. Plant
Avg. Plant
Avg. Leaf
Avg. Leaf
Avg. Leaf
Avg. Leaf
Leaves
Leaves
1a 0.1 0 0 0 0 0 0 0
2a 0.8 0 0 0 0.3 0 0 0
3a 1.6 3 0.1 0.2 0.8 2 0.1 0.2
4a 3.9 9 0.8 1.1 2.9 6 0.5 0.7
1b 0.1 0 0 0 0.1 0 0 0
2b 0.7 0 0 0 0.4 0 0 0
3b 1.9 4 0.2 0.4 0.7 2 0.1 0.2
4b 3.5 8 0.7 1.2 3.0 7 0.5 0.6
Table D. Post-harvest plant data for plants grown in loam and silt for trial two
Total Plant
Avg. Plant
Avg. Stem
Avg. Stem
Avg. Leaf
Soil Type
Mass (g)
Mass (g)
Mass (g)
Mass (g)
Length
(cm)
Loam 5.5 1.1 0.2 0.9 4.1
Silt 4.9 0.98 0.2 0.8 3.1
4.5
Average Plant Height (cm)
4
3.5
3
2.5
2 Loam
1.5
Silt
1
0.5
0
1 2 3 4
Week
Figure A. Line chart comparing average plant height each week
for loam vs. silt
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