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Running title: Planting density of Indian Spinach in an Aquaponics System Optimization
of Planting Density of Indian Spinach in a Recirculating Aquaponics System Using Nile
Tilapia Md. Amzad Hossaina*, Ashrafula, Taslima Akhtera, Masuma Akter Sadiaa,
Tasmina Akterb and Kazi Ahsan Habibc aDeapartment of Aquaculture, Bangabandhu
Sheikh Mujibur Rahman Agricultural University, Gazipur 1706, Bangladesh
bDeapartment of Fisheries Management, Bangabandhu Sheikh Mujibur Rahman
Agricultural University, Gazipur 1706, Bangladesh cDepartment of Fisheries Biology and
Genetics, Sher-e-Bangla Agricultural University, Dhaka, Bangladesh *Corresponding
author: Tel. +880-1711150059, Fax.
+88029205316; e-mail: [email protected] Abstract. An experiment was conducted
for 10 weeks to compare the effect of planting density on the growth and yield of Indian
spinach (Basella alba) and Nile tilapia (Oreochromis niloticus) in a recirculating
aquaponics system. Indian spinach were planted at four densities (4 plants/m2, 8
plants/m2, 12 plants/m2, and 16 plants/m2).
Stocking density of Nile tilapia (32.5 g) was 45 fish/tank (water capacity 300 L) in all
planting densities. The highest weight gain, percent weight gain, specific growth rate
and protein efficiency ratio of fish were obtained in 12 plants/m2 planting density. Feed
conversion ratio was the lowest in 12 plants/m2.
Number of leaves per plant, plant length, plant weight and yield of Indian spinach
showed significant highest results in 12 plants/m2. It was concluded that 12 plants/m2
for Indian spinach, integrated with 45 fish/tank, is suitable for production of both the
plant and Nile tilapia in a recirculating aquaponics system.
Keywords: Indian spinach, Nile tilapia, planting density, growth, feed utilization
Introduction Aquaponics is an example of an integrated system, since in these systems
the plants utilize fish waste as a source of nutrients, minimizing the negative
environmental impact caused by discharge of fish culture water (Savidov et al., 2005).
This symbiotic interaction in the system can reduce the need for filters, fertilization,
mechanical maintenance, water monitoring and water changes as compared to
aquaculture or hydroponics alone (Rakocy et al., 2004). Combining hydroponics and
aquaculture allows the chemical nutrients needed for hydroponics plant growth to be
replaced with fish wastes that might otherwise be discharged and cause potential
environmental degradation (Mancosu et al., 2015). In most aquaponics systems, fish are
fed with a high-protein diet (Rakocy et al.,
2006; Rakocy, 2012). Therefore, the fish excrete wastes that contain potentially toxic
nitrogen compounds, including ammonia (NH3), through their gills as well as in their
feces. These compounds are first processed into nitrite and then nitrate by nitrifying
bacteria (nitrosomonas and nitrobacteria, respectively) in the system.
The plants utilize the nitrate from the water for growth, serving as a bio-filter of
nutrients and thereby reducing the need for active biological or chemical filtration and
water quality management. As the plants remove waste from the water, they also reduce
the need to replace water for the fish tanks (Goddek et al., 2015). Small to medium-scale
aquaponics systems require very little space and can be used in homes, backyards,
basements, balconies and rooftops to increase personal and community food security
(Rakocy, 2012). Savidov et al.
(2005) stated that the integration of fish and plant systems can potentially reduce the
amount of water used per kilogram of food produced. Selection of fish species and
plant variety for any aquaponics system is important. In this context, the available
farmed species, Nile tilapia (Oreochromis niloticus) is among the best candidates for
culture in aquaponics.
It is preferred by farmers as an aquaponics species because of its suitable features for
aquaculture such as faster growth rate compared to other short cycled fish species
(Moya et al., 2014; Goddek et al., 2015; Kawser et al. 2016, Raihan et al., 2018). In case of
plant the green leafy vegetables grow well in the hydroponics sub-system, although
most profitable varieties are Chinese cabbage, lettuce, basil, roses, tomatoes, okra,
cantaloupe and bell peppers (Love et al., 2015; Bailey and Ferrarezi, 2017).
Indian spinach (Basella alba) is a popular summer leafy vegetable, which belongs to the
family Basellaceae. The nutritive value of Indian spinach is very high with a good content
of minerals, vitamins and substantial amount of fiber (Sanni, 1983). Plant spacing has a
marked effect on growth and development of crops (Wongkiew et al., 2017). It is an
important aspect of crop production for maximizing the yield.
Densely planted crops obstruct the proper growth and development of plant. On the
other hand, wider spacing ensures the basic requirements but decrease the total
number of plants as well as total yield. Yield may be increased up to 25% by using
optimum spacing (Bansal and Verreth, 1995).
Specially planting density is important for aquaponics system, because, it is crucial to
know, how many plants are sufficient to utilize wastes produced in the fish culture tank.
However, most of the researches have been conducted on stocking density of fish in
aquaponics system but not the planting density of vegetable (Cruz, 2001; Watanabe et
al., 2002; Kawser et al., 2016; Raihan et al., 2018).
In an aquaponics system, it is also important to monitor water quality parameters,
whether they are suitable for fish. Therefore, the primary goal of this study was to
evaluate the effect of planting density on the growth and yield of Indian spinach and
Nile tilapia in a recirculating aquaponics system.
Materials and Methods The present experiment was conducted for a period of 10 weeks
to determine the effect of planting density on the growth and yield of Indian spinach
and Nile tilapia in a recirculating aquaponics system. The experiment was conducted in
the backyard Aquaponics Shed of Faculty of Fisheries, Bangabandhu Sheikh Mujibur
Rahman Agricultural University, Gazipur, Bangladesh.
Establishment of recirculating aquaponics system. The design of aquaponics system was
closely mirrors that of recirculating systems in general, with the addition of a
hydroponics component and the elimination of a separate bio-filter and devices for
removing fine and dissolved solids. Fish were reared in round plastic tanks (300 liters
water capacity).
The fish rearing tanks were placed in ground level under a shed. Steel sheets made
vegetable trays of 0.15 m3 (125 cm × 85 cm × 15 cm) size were placed above a stage
under shed. All the vegetable growing trays were filled with pieces of small size (8-15
mm) gravels. The experiment was conducted in triplicate. Separate recirculation system
was established for each set of fish rearing tank and vegetable tray.
At first the fish rearing tank was filled with water. A water pump of 12 watt capacity was
set into the tank to pump water to vegetable tray through a plastic pipe. Water from the
vegetable trays entered into the fish rearing tanks by gravitational force. Thus, a
recirculating aquponics system was established where the nutrient rich water (worked as
plant fertilizer) from the fish rearing tanks was pumped into the vegetables bed (worked
as a bio-filter) and clean water re-entered the fish rearing tanks and produced fish and
vegetables simultaneously in an eco-friendly manner.
Stocking and rearing of Nile tilapia. A total of 850 monosex Nile tilapia were collected
from a local commercial fish hatchery (Sagor Motso Hatchery), Mymensingh. The fish
were transported in the experimental site in oxygenated polythene bag. Then the fish
were kept in 500 L tanks for 7 days for conditioning. The fish were weighed individually,
selected and distributed as 45 fish into each of the 300 L tanks in such a way that the
total weights of fish in all tanks were similar. All tanks were uniformly aerated with
aquarium aerators (Hailea, ACO 308).
Fish were fed to satiation with commercially available floating tilapia pellets containing
11.3% moisture, 30.0% protein, 3.8% crude lipid and 10.2% ash. Cultivation of Indian
spinach. Indian spinach seeds were collected from local market. Then the seeds were
sowed in the adjacent agriculture land. Then 15 days old Indian spinach plants were
transplanted in aquaponics units. The planting densities were, 4 plants/m2 (spacing 25.0
cm x 17.0
cm), 8 plants/m2 (spacing 13.5 cm x 9.5 cm), 12 plants/m2 (spacing 9.5 cm x 6.5 cm) and
16 plants/m2 (spacing 7.5 cm x 5.0 cm). No supplemental fertilizer was used during
plant cultivation except the nutrient received from the water coming from fish rearing
tanks. Sampling of fish. Fish were sampled fortnightly and growth and survival
monitored. At the end of 10 weeks rearing period, all fish in all tanks were counted for
survival data.
Fish were killed by anaesthetization with MS-222 (3-aminobenzoic acid ethyl ester, 100
mg/l). Length and weight of 10 fish were taken to determine the growth performance.
Ten carcasses (dead body) from each tank were pooled, washed with distilled water and
stored at -20 0C for whole body chemical composition analysis. Indian spinach data
collection. Numbers of leaves of 4 randomly chosen plants were counted after 24, 42, 56
and 70 days after planting (DAP).
All the leaves of each plant were counted. Only the smallest young leaves at the growing
point of the plant were excluded from counting. The average of leaves of 4 plants gave
the number of leaves per plant. Then, length was measured in cm by a meter scale. The
average of length of 4 plants gave the plant length. The first harvesting of Indian
spinach was done from all trays after 24 DAP.
The plants were cut manually at a length of 6 inch from the bed level by a pair of
scissors. Yield (biomass) was measured by collectively weighing all the plants harvested.
The plants were allowed to grow and the subsequent three harvests were done after 42
DAP, 56 DAP and 70 DAP and the yields on harvesting dates and total yield were
recorded. Plant weight was measured in g by an electronic balance (Simadzu, Japan, ATX
324). The average of weight of 4 plants gave the plant weight.
Monitoring water quality. Water quality parameters from fish growing tanks were
measured fortnightly between 8.0 and 9.0 a.m. during the study period following the
standard methods of APHA (2012). The Water temperature (°C) was recorded using a
Celsius thermometer (9313C39, Thomas) and pH by a digital pH meter (HQ11D, HACH)
at the fish rearing tanks.
For the chemical analysis water samples were collected in black plastic bottles having a
volume of 250 ml each and marked with treatment number. Then the water samples
were examined in the laboratory for chemical analysis. Hydrogen ion concentration (pH)
of tanks water was measured by using a digital pH meter (HQ40D, Hach Co., Colorado,
USA).
Ammonia (mg/l), nitrate (mg/l), nitrite (mg/l) and phosphate (mg/l) were determined
with a spectrometer (DR 5000, Hach Co., Colorado, USA). A digital DO meter (HQ30D,
Hach Co., Colorado, USA) was used to determine the dissolved oxygen content of water.
Chemical analysis of sample. The proximate composition of Indian spinach, fish and feed
samples was determined according to standard method given by the Association of
Official Analytical Chemists (AOAC, 1995). Growth parameters of fish.
Growth of fish in length (cm) and weight (g) was measured and the following
parameters were used to evaluate the growth: 1. Weight gain % = Mean final
weight-Mean initial weight Mean initial weight ×100 2. Specific growth rate % day -1 =
ln W t-ln W 0 t ×100 where, Wt and W0 are the average weight of fish at time t and 0,
respectively and t is the culture period in day. 3. Condition factor CF (%) = _Fish weight
in g _× 100 _ _ _(Fish length in cm) 3 _ _ _ 4.
Survival Rate (%) = _Total number of fish harvested _× 100 _ _ _Total number of fish
stocked _ _ _5. Feed conversion ratio (FCR) = _Total weight of dry feed intake (g) _ _
_Total wet weight gain (g) _ _ Gain in body mass (g) 6. Protein efficiency ratio (PER) =
Protein intake (g) Statistical analysis.
The data were analyzed statistically by one-way analysis of variance (ANOVA) using
statistical software Statistix 10 (Analytical Software, Tallahassee, FL), where significant
differences in means were compared by Least Significant Difference (LSD) option of the
package. Normality and homogeneity were tested with Sapiro-Wilk test and Levene test,
respectively. The significance level was determined at p<0.05.
Results and Discussion Water quality parameters are presented in Table 1. The average
water temperature varied between 28.77 ± 0.21 and 29.00 ± 0.26 °C and was not
significantly different among treatments. As a well-adapted fish, Nile tilapia have
tolerance of a wide range of temperature 20-35 °C for growth where the optimum
temperature is reported between 26 and 28 °C within which productivity can be
assumed at maximum (De Schyver et al., 2008; Crab et al., 2009).
According to Colt (2006) optimal water temperature for life of Nile tilapia is 28 °C. On
the other hand, nitrifying bacteria grow well in temperature 28-30 °C (Wongkiew et al.,
2017). Therefore, the temperature found in this experiment was appropriate for fish
culture and nitrification process in aquaponics system.
The average pH level of water during the experimental period ranged from 7.25 to 7.67.
However, water pH was not significantly different among the treatments (p>0.05). pH in
water body generally regulates considerably the water chemistry. Any sudden
fluctuation of pH causes the death of many aquatic species. Boyd (1998) reported that
the suitable pH range for fish production were 7.3 to 8.4. Nile tilapia can tolerate a pH
range of 4 to 11 and pH between 6.5 and 9.0
is the desirable range for Nile tilapia culture (Huet, 1972). Therefore, in the present
study, the pH value was suitable for Nile tilapia growth. The nitrifying bacteria growth is
inhibited below a pH of 6.5 with an optimum pH at 7.8 depending on species and
temperature (Tyson et al., 2007). Therefore, the range of pH value found in present study
was also good for nitrification.
The optimum ammonia level in a recirculatory system should be less than 1.0 mg/l (Van
Rijn and Rivera, 1990). In the present study, the ammonia-nitrogen level of tank water
ranged between 0.49 and 0.74 mg/l (Table 3). Ammonia is produced as a product of
protein catabolism (Wood, 1993).
The overall ammonia contents in all treatments increased with the progress of culture,
however, within the suitable limit for Nile tilapia. However, there was no significant
difference (p>0.05) among water ammonia-nitrogen level in a sampling date during the
experimental period. It indicated that the value of ammonia was within safe limit of fish
(Kamal, 2006). The nitrate level of tank water ranged between 35.00 and 36.95 mg/l.
Tank water nitrate in a sampling day was not significantly differing (p>0.05) during the
experimental period. According to Rakocy et al. (2004) optimum range of nitrate was
26.7 mg/l to 54.7 mg/l for batch culture during basil production trials with Nile tilapia.
Licamele (2009) recorded concentrations of 50 mg/l N-NO3 in an aquaponics integrated
system with lettuce (Lactuca sativa) and Nile tilapia (Oreochromis niloticus) were safe for
culture. Nitrogen is important component for plant growth and plant obtain this
nitrogen from fish excreta in the form of ammonia.
In an aquaponics system ammonia is first converted into nitrite and then nitrate by
nitrifying bacteria. Plant use this nitrate as a source of nitrogen for their growth. On the
other hand too much nitrogen and to low nitrogen limit the growth of plant (Sabidov et
al., 2005; Goddek et al., 2015).
For this reason, in this experiment the production of plant was highest at 12 plants/m2
planting density, because plants in the culture bed got proper amount of nitrogen. On
the other hand in planting density of Indian spinach at 4 and 8 plants/m2 plants
received excessive amount nitrogen that limited the growth. Again at 16 plants/m2
planting density of Indian spinach, the plant lacked nitrogen that limited the plant
growth.
Kamal (2006) stated that recommended concentration of nitrite in culture system was
less than 0.15 mg/l for culture of Nile tilapia in a mini pond. According to Rakocy et al.
(2004) range of nitrate was 0.4 mg/l to 1.1 mg/l for batch culture during basil
production trials. From the above statements, the level of nitrite in the present study
was within the productive range and suitable for fish and vegetable culture.
In the present study, the phosphate level of tank water ranged between 2.85 ± 0.47 and
3.04 ± 0.20 mg/l (Table 1). Tank water phosphate was not significantly different (p>0.05)
during the experimental period. Boyd (1998) reported that tolerable limit of phosphates
in aquaponics system is between 0.20 and 1.15 ppm. Stefan et al.
(2013) conducted a research on vegetable production in an integrated aquaponics
system with rainbow trout and spinach and recommended that phosphate
concentration in aquaponics system ranges from 1.5 mg/l to 3.7 mg/l. So, the
phosphorous level of the present study was within suitable range. In the present study,
dissolve oxygen (DO) level of tank water ranged between 5.46 and 5.72 mg/l (Table 1).
There was no significant difference (p>0.05) in water DO during the experimental
period. Maintenance of DO is important for fish health and aerobes of biofilter (Hussain
et al., 2015).
Nile tilapia needs 5 mg/l dissolved oxygen for optimal growth, and if the concentration
falls below 2.5 ppm there have significant growth retardation of fish (Masser et al.,
1999). Similarly, activity of nitrifying bacteria to convert harmful ammonia to less
harmful nitrite is also dependent on DO.
Nitrifying bacteria are known to become inefficient at DO level bellow 2 mg/l (Masser et
al., 1999). From the above statement, it is clear that the levels of dissolved oxygen in all
the treatments were found to be in favorable range. Growth response of Nile tilapia. The
average weight gain of Nile tilapia was 42.11 ± 1.82 g, 42.18 ± 2.15 g, 46.34 ± 0.14 g
and 40.70 ± 2.96 g in 4, 8, 12 and 16 plants/m2 planting density of Indian spinach,
respectively (Table 2).
Significant higher weight gain observed in 12 plants/m2 and lower weight gain
observed in 16 plants/m2 planting density of Indian spinach. Data on fish length
followed the similar trend. The average percent weight gain of Nile tilapia was 129.37 ±
1.41, 129.70 ± 1.41, 141.89 ± 1.41 and 126.05 ± 1.41 in 4, 8, 12 and 16 plants/m2
planting density of Indian spinach, respectively. Significant higher percent weight gain
observed in 12 plants/m2 (141.89 ± 1.41) and lower observed in 16 plants/m2 (126.05 ±
1.41).
As plant production was higher in 12 plants/m2 than the other treatments, therefore fish
production in this planting density was higher. Because more plants had purified water
properly and fish got clean and NH3-free water that enhanced the growth of fish. Kamal
(2006) obtained maximum growth of Nile tilapia when cultured with bell pepper at a
planting density of 10 plants/m2. Effendi et al.
(2017) observed that addition of romine lettuce in the culture system increase the
biomass of Nile tilapia. Wongkiew et al. (2017) observed that introducing lettuce in the
fish culture system decrease the nutrient concentration in the system. In the present
study, the maximum growth of Nile tilapia with 12 fish/m2 was similar to above
statements.
The survival rate of Nile tilapia was 100, 100, 100 and 98.88±1.57% in 4, 8, 12 and 16
plants/m2 planting density of Indian spinach, respectively (Table 2). The survivability of
fish observed in the present study was high, which was similar to those reported for Nile
tilapia in aquaponics system (Al-Hafedh et al., 2008; Bakhsh and Chopin, 2012; Wang et
al., 2016). However, planting density did not affect the survivability.
Significant higher SGR of Nile tilapia was observed at 12 plants/m2 planting density of
Indian pinash, whereas SGR in at 4 plants/m2 and 8 plants/m2 planting were similar to
12 plants/m2 (Fig. 1). Lower SGR observed in 16 plants/m2 planting density. Midmore
(2011) obtained a slightly higher SGR value 2.03(% day-1) with Nile tilapia in Honduras
using pellet and fertilizer. Hussain et al. (2015) observed SGR value of GIFT strain ranged
from 2.04 to 2.30 (% day-1) fed with formulated diet, which is higher than the values of
present study. Kamal (2006) obtained SGR value of 1.6
(% /day) in a aquaponics production of Nile tilapia (O. niloticus) and Bell pepper
(Capsicum annuum) in recirculating aquaponics system. In the present study the SGR
value was slightly lower than the findings of SGR value of fish in aquaponics system
obtained by Kamal (2006), which may be due to differences in stocking density and
culture environment.
The condition factor (CF) indicates the well-being of a fish and is based on the
hypothesis that heavier fish of a given length are in better condition (Bagenal and Tesch,
1978). The CF of Nile tilapia in the present study ranged from 1.84 ± 0.02 to 2.11 ± 0.03
(Table 2). Significant higher CF (2.11 ± 0.03) was observed in 12 plants/m2 and the lower
CF (1.84 ± 0.02) was observed in 4 plants/m2, 8 plants/m2 and 16 plants/m2,
respectively.
Ayode (2011) reported that higher condition factor of fish indicate good health, which is
desirable for fish in fish farms as observed at 12 plants/m2 planting density in the
present study. Feed utilization. The highest feed conversion ratio (FCR) was observed in
8 plants/m2 planting density of Indian spinach, while the lowest FCR was found in 12
plants/m2 planting density (Fig. 2).
The FCR value in 12 plants/m2 planting density indicated better feed utilization because
of more plant purifies water and fish get clean water and effectively utilize the feed.
Watanabe et al. (2002) in a study with Nile tilapia found FCR values of 1.5-2.0. The FCR
values for Nile tilapia in the present aquaponics system was better than that of other
studies. Significant highest protein efficiency ratio (1.61) was observed in 12 plants/m2
while the lowest (1.41) protein efficiency ratio was observed in 16 plants/m2 (Fig. 3).
Protein efficiency ratio of Nile tilapia was 1.17 and 1.23 using floating and sinking
pellets, respectively in a recirculating aquaponics system (Cruz, 2001). Protein efficiency
ratio of Cyprinus carpio was 1.34 in an aquaponics system with spinach as a hydroponic
crop (Hussain et al., 2015). Using castor seed meal as feed ingredient for Nile tilapia
protein efficiency ratio was 1.52 in a recirculating aquaponics system (Balogun et al.,
2005).
Protein efficiency ratio of the present study was similar compared to most of the
previous studies and a planting density of 12 plants/m2 created a favorable
environment for protein utilization in fish. Proximate composition of whole body
carcasses. The average moisture, protein, lipid and ash of Nile tilapia varied within 73.56
± 0.58-74.36 ± 0.14, 18.13 ± 0.01-18.81 ± 0.01, 5.03 ± 0.21-5.87 ± 0.27, 1.54 ± 0.09-1.88
± 0.04, respectively (Table 3).
However, there was no significant difference in those values, i.e., planting density of
Indian spinach did not exert any influence on fish carcass composition. Whole body
carcass composition of tilapia mostly affect by the nutrient composition of diet
especially the protein (Foh et al., 2011). In the present experiment, fish in all treatments
received the same diet, i.e. same level of nutrients, therefore, whole body carcass
composition was not different.
Vegetable growth performance. Number of leaves per plant of Indian spinach varied
significantly due to different planting densities after 24, 42, 56 and 70 DAP (Table 4).
Number of leaves per plant was the highest at 12 plants/m2 planting density in each of
the sampling dates.
Similarly plant length and plant weight were the highest in 12 plants/m2 in all the
sampling dates. In the present study, number of leaves per plant, length per plant and
weight per plant were significantly different and those values were significantly higher in
12 plants/m2 planting density.
In an aquaponics system plant gets nitrogen from fish waste as the form of ammonia
which then converts to nitrite and then nitrate by the process nitrification. The yield of
Indian spinach per treatment varied significantly due to different planting density after
24, 42, 56 and 70 DAP, which are shown in Table 5. Total yield of Indian spinach per
meter square varied significantly due to different planting density (Table 5). The highest
total yield (5.347 kg/m2/70 days) was recorded at planting density of 12 plants/m2 ,
while the lowest (0.777 kg/m2/70 days) yield was found in 4 plants/m2.
At the planting density of 12 plants/m2 plant got suitable amount of nitrogen for their
growth on the other hand in 4 plants/m2 plant got excessive amount of nitrogen that
hampered growth of plant and in 16 plants/m2 plant did not get enough nitrogen for
their growth. Abbasdokht et al. (2003) observed in case of amaranth that the density
with 40 plants/m2 gave the minimum yield, whereas 10 plants/m2 gave the highest
yield.
Kamal (2006) studied on aquaponics production of Nile tilapia (O. niloticus) and Bell
pepper (C. annuum) in re-circulating water system. The results showed that fish cultured
with 10 plants/m2 gave the best significant (P<0.05) fish production and yield of
marketable Bell pepper. Therefore, a planting density of 12 plants/ m2 can be
considered as optimum for vegetable production.
The present study indicates that weight gain, percent weight gain, specific growth rate,
condition factor, food conversion ratio, and protein efficiency ratio of Nile tilapia were
affected by planting density of Indian spinach and the best results were obtained in 12
plants/m2 planting density of Indian spinach . Similarly in case of vegetable growth and
yield the present study indicates that number of leaves per plant, plants length per
plant, plants weight per plant and yield of Indian spinach was better in 12 plants/m2.
Conclusion This study revealed that a planting density of 12 Indian spinach/m2
integrated with 45 Nile tilapia/300 l water was suitable for both Indian spinach and Nile
tilapia. Farmer can utilize this plant to fish ratio for effective running of an aquaponics
system. Acknowledgement This study was conducted with a fund from Bangabandhu
Sheikh Mujibur Rahman Agricultural University which is gratefully acknowledged.
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experimental period Parameters _Planting density of Indian spinach (plants/m2) _ _ _4 _8
_12 _16 _ _Temperature (°C) _28.77 ± 0.21 _28.22 ± 0.26 _28.59 ± 0.22 _29.00 ± 0.26 _
_pH _7.25 ± 0.21 _7.67 ± 0.15 _7.51 ± 0.24 _7.45 ± 0.06 _ _O (mg/l) _5.66 ± 0.12 _5.52 ±
0.10 _5.46 ± 0.09 _5.72 ± 0.15 _ _NH3-N (mg/l) _0.74 ± 0.18 _0.52 ± 0.25 _0.64 ± 0.19
_0.49 ± 0.16 _ _NO2-N (mg/l) _0.12 ± 0.02 _0.13 ± 0.02 _0.12 ± 0.04 _0.11 ± 0.05 _
_NO3-N (mg/l) _1.06 ± 0.34 _1.10 ± 0.29 _1.20 ± 0.40 _1.15 ± 0.29 _ _PO4-P (mg/l) _2.85
± 0.47 _2.93 ± 0.53 _2.89 ± 0.29 _3.04 ± 0.20 _ _ Table 2.
Growth data of tilapia in different planting densities after 70 days of rearing Parameters
_Planting density of Indian spinach (plants/m2) _ _ _4 _8 _12 _16 _ _Initial weight (g)
_32.55 ± 0.62 _32.52 ± 0.29 _32.66 ± 0.35 _32.29 ± 0.22 _ _Final weight (g) _74.66b ±
1.19 _74.70b ± 2.45 _79.00a ± 0.08 _72.99c ± 2.94 _ _Weight gain (g) _42.11b ± 1.82
_42.18b ± 2.15 _46.34a ± 0.14 _40.70c ± 2.96 _ _Weight gain (%) _129.37 b ± 1.41
_129.70b ± 1.41 _141.89a ± 1.41 _126.05c ± 1.41 _ _Initial length (cm) _8.30 ± 0.04 _8.17
± 0.26 _8.26 ± 0.41 _8.05 ± 0.24 _ _Final length (cm) _15.79b ± 0.01 _15.84b ± 0.43
_16.25a ± 0.1 _15.89b ± 0.07 _ _Length gain (cm) _7.49c ± 0.06 _7.67b ± 0.16 _7.99a ±
0.31 _7.84ab ± 0.16 _ _Condition factor _1.89b ± 0.02 _1.85b ± 0.03 _2.12a ± 0.02 _1.82b
± 0.04 _ _Survival rate (%) _100.0 _100.0 _100.0 _98.9 ± 1.6 _ _* Means in a raw with
different superscript are significantly different (p<0.05). Table 3.
Proximate composition of whole body carcasses of tilapia fed with floating pellets in
different planting densities Planting density of Indian spinach (plants/m2) _Parameters _
_ _Moisture% _Protein% _Lipid% _Ash% _ _4 _73.56 ± 0.58 _18.17 ± 0.18 _5.03 ± 0.21
_1.79 ± 0.12 _ _8 _73.61 ± 0.14 _18.43 ± 0.41 _5.74 ± 0.01 _1.72 ± 0.22 _ _12 _74.36 ±
0.04 _18.81 ± 0.01 _5.87 ± 0.27 _1.88 ± 0.04 _ _16 _73.59 ± 0.07 _18.13 ± 0.01 _5.85 ±
1.35 _1.54 ± 0.09 _ _ Table 4.
Growth data Indian spinach in different planting densities observed on different dates
Planting density of Indian spinach (plants/m2) _Days after planting _ _ _24 Day _42 Day
_56 Day _70 Day _ _Number of leaves per plants _ _4 _4.08d ± 0.12 _14.08c ± 0.12 _7.75d
± 0.17 _17.75c ± 0.17 _ _8 _11.12b ± 0.17 _21.12ab ± 0.17 _11.22b ± 0.03 _21.22ab ±
0.03 _ _12 _12.37a±0.17 _22.37a ± 0.17 _14.16a ± 0.05 _24.16a ± 0.05 _ _16 _10.18c ±
0.26 _20.18bc ± 0.26 _9.21c ± 0.04 _19.21b ± 0.04 _ _Length per plant (cm) _ _4 _48.25d
± 2.47 _60.25c ± 3.18 _76.56c ± 3.97 _92.56c ± 3.97 _ _8 _60.96b ± 0.30 _76.96ab ± 0.30
_89.90b ± 0.04 _105.90b ± 0.04 _ _12 _65.71a ± 1.83 _81.71a ± 1.83 _108.97a ± 2.56
_124.97a ± 2.56 _ _16 _55.57c ± 0.29 _71.57b ± 0.29 _65.68d ± 1.54 _81.68d ± 1.54 _
_Weight per plant (g) _ _4 _24.70d ± 1.47 _40.70d ± 1.47 _56.50c ± 1.23 _72.50c ± 1.23 _
_8 _52.96b ± 0.22 _68.96b ± 0.22 _81.87b ± 2.12 _97.87b ± 2.12 _ _12 _69.12a ± 2.12
_85.12a ± 2.12 _137.87a ± 2.53 _153.87a ± 2.53 _ _16 _32.42c ± 0.28 _48.42c ± 0.28
_49.23d ± 1.92 _65.23d ± 1.92 _ _Note: Values are given with mean± standard deviation.
Different lettering in the same columns (for a parameter) are significantly different at
5%. Table 5.
Yield (kg/m2/70 days) of Indian spinach in different planting densities observed on
different dates Planting density of Indian spinach (plants/m2) _Days after planting _ _
_24 Day _42 Day _56 Day _70 Day _Total _ _4 _0.098c ± 0.005 _0.162d ± 0.005 _0.226d ±
0.004 _0.291d ± 0.004 _0.777d ± 0.005 _ _8 _0.423bc ± 0.001 _0.551c ± 0.001 _0.654c ±
0.016 _0.782c ± 0.016 _2.411c ± 0.008 _ _12 _0.829a ± 0.025 _1.021a ± 0.025 _1.651a ±
0.030 _1.846a ± 0.030 _5.347a ± 0.002 _ _16 _0.518b ± 0.004 _0.774b ± 0.004 _0.787b ±
0.030 _1.043b ± 0.030 _3.122bc ± 0.015 _ _Note: Values are given with mean ± standard
deviation.
Value in the same column bearing different letters is significantly different at 5%. / Fig.
1. Specific growth rate of tilapia in different planting densities. Means with different
letters are significantly different (p?0.05). / Figure 2. Feed conversion ratio of tilapia in
different planting densities. Means bearing different letters are significantly different
(p<0.05). / Fig. 3. Protein efficiency ratio of tilapia in different planting densities.
Means bearing different letters are significantly different (p<0.05).
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