Effect of bat guano on the growth of five economically important plant species

Abstract

Fertiliser applications are critical to crop production and food security in Cambodia. While inorganic forms are mostly used, livestock manure, compost and bat guano are also widely applied. As the efficacy of bat guano as a plant fertiliser is unknown in the country, this was tested in eight-week growth trials for five economically important species: horseradish tree Moringa oleifera Lam., jackfruit Artocarpus heterophyllus Lam., longan Dimocarpus longan Lour., eggplant Solanum melongena L. and papaya Carica papaya L. Three treatments were employed in the trial: a control, a chemical fertiliser treatment, and a bat guano treatment. Results indicate that bat guano applications enhance plant growth. Compared to controls, all plant species in the guano treatment exhibited greater growth rates, most of which were statistically significant. Compared with chemical fertiliser treatments, three species in the guano treatment also exhibited greater growth, though only two were significantly different. In the remaining two species, growth was less or similar although again not significantly different. Additional trials are recommended to elucidate any longer term and cumulative benefits that might accrue from the use of bat guano as a plant fertiliser.

Full text

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Agriculture remains the core source of income
for most Cambodians, accounting for 34.7% of
the country’s GDP and 56.7% of national labour
force work in 2012 (Save Cambodia’s Wildlife,
2014). As much of Cambodia’s arable land is
nutrient deficient, access to and use of fertilisers
is critical to agricultural productivity and
national food security (Save Cambodia’s
Wildlife, 2014). Though inorganic (or
synthetic) fertilisers are most commonly
applied, organic forms such as livestock
manure, compost and bat guano are also
extensively used throughout the country. For
instance, harvesting of bat guano for fertiliser
Short communication
Effect of bat guano on the growth of five economically important plant
species
Thi Sothearen
1,*
, Neil M. Furey
1,2
and Joel A. Jurgens
2
1
Centre for Biodiversity Conservation, Room 415, Department of Biology, Faculty of Science, Royal University of
Phnom Penh, Confederation of Russia Boulevard, Phnom Penh, Cambodia
2
Fauna & Flora International (Cambodia Programme), PO Box 1380, No. 19, Street 360, Boeng Keng Kong 1,
Phnom Penh, Cambodia, 12000
Received 6 June 2014; received in revised form 27 September 2014; accepted 29 September 2014.
Abstract
Fertiliser applications are critical to crop production and food security in Cambodia. While inorganic forms are mostly
used, livestock manure, compost and bat guano are also widely applied. As the efficacy of bat guano as a plant fertiliser
is unknown in the country, this was tested in eight-week growth trials for five economically important species: horseradish
tree Moringa oleifera Lam., jackfruit Artocarpus heterophyllus Lam., longan Dimocarpus longan Lour., eggplant Solanum
melongena L. and papaya Carica papaya L. Three treatments were employed in the trial: a control, a chemical fertiliser
treatment, and a bat guano treatment. Results indicate that bat guano applications enhance plant growth. Compared to
controls, all plant species in the guano treatment exhibited greater growth rates, most of which were statistically significant.
Compared with chemical fertiliser treatments, three species in the guano treatment also exhibited greater growth, though
only two were significantly different. In the remaining two species, growth was less or similar although again not
significantly different. Additional trials are recommended to elucidate any longer term and cumulative benefits that
might accrue from the use of bat guano as a plant fertiliser.
Key words: Organic manuring; Plant growth
has occurred for decades at sites inhabited by
the cave-dwelling Asian wrinkle-lipped bat
Chaerephon plicatus (Buchannan, 1800)
. In
addition, creation of artificial roosts colonised by
the foliage-dwelling lesser Asiatic yellow house
bat Scotophilus kuhlii Leach, 1821 whose guano
is collected for fertiliser is widespread in the Pursat,
Kandal and Takeo provinces (CBNRMLI, 2009;
Chhay, 2013). This intriguing practice of
establishing free-ranging bat colonies for on-farm
guano collection appears to be unique to Cambodia
and small neighbouring areas of Vietnam (Furey,
2012).
Although bat guano is commonly traded and
used as fertiliser in Cambodia, empirical studies
*Author for correspondence: Phone +855-17907905; E-mail: <sothearenthi@yahoo.com>.
Journal of Tropical Agriculture 52 (2) : 169-173, 2014

170
of its efficacy have yet to be conducted.
Consequently, the aim of the study was to test
whether bat guano applications actually do
improve plant growth, and should this prove the
case, to determine how favourably this
enhanced growth compares to that obtained
using chemical fertilisers.
Five multi-purpose species were selected for the
study (Table 1). These were selected based on
their availability in Cambodia, local knowledge
and markets or were species that have beneficial
attributes related to nutrition, human health, the
environment or a combination of these. The
growth trial was undertaken at the biological
field research laboratory of the Royal University
of Phnom Penh from March to July 2013. Three
treatments were adopted in the trial: i) a control,
with no fertiliser applications; ii) a chemical
fertiliser treatment; and, iii) a bat guano
treatment. Each treatment consisted of 10
replicates per species which were grown for
eight weeks under shade netting at the
laboratory, providing a total sample of 30
individual plants for each species (or a study
total of 150 plants).
All plants in the trial were grown from seed at
the laboratory. Seeds were obtained for two
species (C. papaya and S. melongena) from the
Chua Yong Seng Seed Company in Phnom
Penh, while seeds for A. heterophyllus and D.
Attributes
Shrub or small tree. Young leaves provide a good source of protein, vitamins A, B and C and minerals
such as calcium and iron (Radovich, 2011; Orwa et al., 2009). Various parts are effective in treating
dental conditions, digestive disorders, skin conditions, circulatory issues and parasitic growth
(Agbogidi and Ilondu, 2012). Also used for fuel wood, living fences, animal fodder and soil stabilisation
(HDRA, 2002) and leaf extractions can increase vegetable yields (Culver et al., 2012a, b).
Large tree. Produces a fruit which can weigh >30 kg in cultivation. Fruit and seeds are edible, and
timber is relatively high quality and used in the manufacture of furniture and music instruments (Dy
Phon, 2000). Jackfruit also has anti-bacterial, anti-inflammatory, anti-diabetic, anti-oxidant and
immune-modulatory properties which are used for medicinal purposes (Prakash et al., 2009).
Annual herb. Widely cultivated for its edible fruit. Eggplant can be eaten raw or cooked and is a good
source of vitamin B, C, calcium, iron phosphorus and potassium (Dy Phon, 2000). Various parts of
the plant have also been found to provide benefits such as antioxidants, anti-fungal properties and
increase cardiovascular health (Noda et al., 2000).
Large herb. Widely cultivated for its large fruit which can weigh as much as 9 kg. The fruit is a good
source of vitamin A, C, E and potassium and magnesium. Other parts of the plant can be used to treat
numerous ailments associated with warts, corns, sinuses, eczema, cutaneous tubercles, glandular
tumors, blood pressure, dyspepsia, constipation and amenorrhoea (Aravind et al., 2013).
Tree or shrub. Widely cultivated for its sweet fruit. Once free from its kernel, the arillus can be
candied in sugar, dried or eaten fresh. Fruit, seed and flowers are used in traditional medicine to
relieve neural pain and swelling (Yang et al., 2011). Pharmacological activities including anti-
tyrosinase, anti-glycated and anti-cancer activities, and memory-enhancing effects of the longan
arillus, pericarp and seed extract have also been found (Yang et al., 2011; Huang et al., 2012).
Species
Horseradish
tree
Moringa
oleifera Lam.
Jackfruit
Artocarpus
heterophyllus
Lam.
Eggplant
Solanum
melongena L.
Papaya
Carica
papaya L.
Longan
Dimocarpus
longan Lour.
Table 1: Summary attributes of plant species employed in the growth trials.
Effect of bat guano on the growth of five economically important plant species

171
longan were obtained from private growers in
Phnom Penh, and for M. oleifera from private
growers in Pursat province. Three seeds were
germinated for each replicate which consisted
of a plastic soil bag (measuring 8 cm in diameter
x 20 cm in height) filled with alluvial soil
obtained from the banks of the Mekong River.
The most robust of the three germinating seeds
was retained and each species was monitored
daily to determine its time to germination. The
growth trials began 1-2 weeks after germination
in all five species and treatments for each
species were undertaken concurrently.
In all treatments, replicates were watered twice
a day for the entire study period (as well as the
post-germination period prior to the trial) and
checked daily for potential insect and/or disease
damage, with removal and/or cleaning
undertaken as needed. For the chemical fertiliser
treatment, granular fertiliser produced by the
Binh Dien Fertiliser Joint-Stock Company was
obtained in Phnom Penh which consisted of
20% nitrogen (N), 20% phosphorus (P) and 15%
potassium (K) (by weight). For the bat guano
treatment, guano produced by S. kuhlii was
obtained from farmers in Kandal province. This
Table 2: Variations in weekly growth of five plant species subjected to three treatments over eight
weeks. Values are given in centimetres as mean, ± SD (minimum-maximum).
Species / Response variable Treatment p
Control Chemical Bat Guano
(n=10) Fertiliser (n=10) (n=10)
Moringa oleifera
stem circumference 1.72 ± 0.58 1.96 ± 0.69 1.93 ± 0.74
(0.80–3.10) (1.00–3.30) (0.90–3.50) 0.026
stem height 59.74 ± 32.35 66.21 ± 37.20 59.32 ± 34.57
(10.0–112.50) (12.00–145.00) (12.80–139.00) 0.125
Artocarpus heterophyllus
stem circumference 1.62 ± 0.30 1.58 ± 0.28 1.78 ± 0.42
(1.10–2.40) (1.10–2.30) (1.00–2.90) <0.001
stem height 33.27 ± 9.08 26.39 ± 9.00 35.60 ± 10.78
(16.00–55.20) (8.00–53.70) (13.00–62.50) <0.001
Solanum melongena
stem circumference 1.22 ± 0.32 1.30 ± 0.45 1.66 ± 0.51
(0.60–2.00) (0.50–2.20) (0.50–2.60) <0.001
stem height 11.67 ± 7.41 13.76 ± 9.67 21.50 ± 13.26
(1.50–26.20) (1.50–40.20) (2.00–47.20) <0.001
Carica papaya
stem circumference 1.82 ± 0.80 2.99 ± 1.72 2.99 ± 1.19
(0.80–4.10) (0.80–10.00) (1.00–5.40) <0.001
stem height 18.63 ± 11.68 34.26 ± 21.58 28.76 ± 14.49
(1.70–48.50) (4.50–106.00) (3.50–56.50) <0.001
Dimocarpus longan
stem circumference 0.92 ± 0.17 0.96 ± 0.14 1.06 ± 0.15
(0.40–1.50) (0.70–1.30) (0.80–1.40) 0.010
stem height 9.37 ± 3.58 8.15 ± 2.08 9.89 ± 2.47
(3.50–18.00) (3.30–12.50) (4.00–16.50) 0.297
Thi Sothearen, Neil M. Furey
and Joel A. Jurgens

172
was tested for macronutrient content in Phnom
Penh and comprised 9.97% N, 3.4% P and 0.4%
K (by weight). In each species treatment, one
gram of chemical fertiliser / bat guano (as
appropriate) was added to each replicate every
seven days for eight weeks, the total application
being comparable to similar studies (Sridhar et
al., 2006; Shetty et al., 2013).
Two response variables reflecting plant growth
were measured (in centimetres) during the trial:
stem circumference (taken just above soil level)
and stem height. Both were measured at seven
day intervals for eight weeks, immediately prior
to the weekly bat guano and chemical fertiliser
applications. The mean weekly value arising
from the eight weeks of measurement of the
two variables for each replicate was employed
in analysis. As these data were normally
distributed (Kolmogorov-Smirnov tests,
p>0.05) and had homogenous variances
(Levene tests, p>0.05), ANOVA were employed
for group comparisons and the Bonferroni
method for pair-wise comparisons.
Bat guano applications enhance plant growth.
Except for stem height in M. oleifera, all of the
five plant species subjected to the bat guano
treatment experienced greater weekly
increments in stem circumference and height
compared to the control (Table 2), and this
difference was statistically significant (p<0.05)
in six of the nine remaining pair-wise
comparisons. Compared to the chemical
fertiliser treatment, three of five plant species
subjected to the bat guano treatment
experienced greater increments in both response
variables, namely A. heterophyllus, S.
melongena and D. longan, although differences
were not significant (p>0.05) in the latter
species. In the remaining two species (M.
oleifera and C. papaya), weekly increments
were less or similar (in the case of stem
circumferences of C. papaya) though once again
these differences were not significant (p>0.05).
That three of the five species treated with bat
guano experienced the greatest growth despite
its lower N-P-K content (9.97-3.4-0.4%)
compared to the chemical fertiliser (20-20-15%)
is noteworthy. Though not yet tested for in
guano produced by S. kuhlii, this is likely
attributable to the presence of organic matter,
carbon, important micronutrients (e.g. calcium,
magnesium, iron, aluminium, iron) and a
beneficial microflora which are typical of
insectivorous bat guano (Sridhar et al., 2006;
Shetty and Sreepada, 2013; Reichard, 2010),
and their absence in the chemical fertiliser. This
is supported by trials in India which suggest
that only small amounts of bat guano are
required to enhance the efficiency of plant
growth (Sridhar et al., 2006; Shetty et al., 2013).
Nonetheless, given the short duration of the
present study it would be instructive to conduct
additional trials to elucidate any longer term and
possibly cumulative effects that may accrue
from bat guano applications. Given the
important role that C. plicatus plays in
consuming major agricultural pests in Thailand
(Leelapaibul et al., 2005), research to determine
the significance of agro-ecosystem services
provided by S. kuhlii is also recommended.
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