Research Paper Vegetable production in a recirculating aquaponic system using Nile tilapia

15 Pages·2014·1.04 MB·English

Academia Journal of Agricultural Research 1(12): 236-250, December 2013
DOI: http://dx.doi.org/10.15413/ajar.2013.0138
ISSN: 2315-7739
©2013 Academia Publishing

Research Paper

Vegetable production in a recirculating aquaponic system using Nile tilapia
(Oreochromis niloticus) with and without freshwater prawn (Macrobrachium
rosenbergii)

Accepted 5th November, 2013

ABSTRACT

Two recirculating aquaponics systems were installed in a controlled environment
greenhouse to study the growth and yield of lettuce (Lactuca sativa), Chinese cabbage
(Brassica rapa pekinensis) and pac choi (Brassica rapa) using Nile tilapia (Oreochromis
niloticus) culture with and without freshwater prawn (Macrobrachium rosenbergii).
Culture water was lifted by a 40 W submersible pump from a 220 L bio-filtration tank
to a 250 L fish tank, and allowed to flow by gravity to a 2.44 × 4.88 m raceway in a
closed loop. Water was maintained at 20 cm depth permitting rafts to float.
Hydroponically germinated seedlings in rockwool blocks were planted on the rafts at
15 cm spacing 30 days after stocking 22 kg of mixed-sex Nile tilapia in the fish tanks
while 295 prawns were added in one of the raceways. Environmental conditions were

maintained and water quality parameters were monitored in a compromise between

the ideal requirements of fish, prawn and vegetables including the beneficial bacteria

throughout the108-day culture period. Two sets of data for the three vegetables and
one for tilapia and prawn were gathered after the two 35 day growing seasons of

vegetables. Results showed that average dissolved oxygen of 5.6 ppm at 98%
Chito F. Sace1*, Kevin M. Fitzsimmons2
saturation and 21°C temperature, and a pH of 7.1‒7.7 were established by the

1Institute for Climate Change and systems that provided a favorable environment for tilapia, prawn and nitrifying
Environmental Management bacteria. However, the pH was disadvantageous to vegetables. With a low
1Central Luzon State University 3120,
concentration of total dissolved solids of less than 330 ppm which was far below the
Science City of Munoz
requirement, the high pH retarded the normal growth of the vegetables resulting in
Nueva Ecija, Philippines
[email protected] chlorotic and necrotic leaves. Results also revealed that the vegetables demonstrated
[phone] significantly better growth in the system with prawns. Among the three vegetables,

pac choi had the highest growth, yield, and productivity followed by Chinese cabbage
2College of Agriculture and Life Sciences,
and lettuce. It was determined that integrating prawn culture helped stabilize and
1703 E. Seventh Street
University of Arizona, Tucson, AZ 85721- diversify the system which aided in improving the harvest. It also confirmed that
0436 U.S.A stocking density and component ratio were critical in designing an aquaponic system.

[email protected]
Key words: Vegetable production, Nile tilapia (Oreochromis niloticus), Nitrosomonas
Phone: [phone]
FAX: [phone] species

INTRODUCTION

Impacts of climate change in Philippine agriculture destructive floods, sea level rise accompanied by barrage of
heat waves and prolonged drought, has made climate change
The Philippines, due to its geographic location, is believed as a persistent challenge for many Filipinos. Scientific studies
one of the most defenceless countries to climate change. also revealed that the country’s foremost water reservoirs
Frequent occurrences of extreme climatic events such as are under threat and could result to severe water shortage
unpredictable pattern of abnormally heavy monsoon rains, (Cayabyab, 2012). With increasing intensity, its impacts
Academia Journal of Agricultural Research; Sace and Fitzsimmons. 237

greatly affect agriculture that will make food production some to be the chinampas of the Aztecs. Many believed that
difficult and food supply unsustainable. This is tantamount aquaponics has originated in Ancient Egypt in the river Nile
to an estimated 5‒7% reduction in the country’s production and in ancient Babylon’s Hanging Garden. Some also said that
of major crops (Buendia, 2010). it started from Far Eastern countries such as China and
Thailand where farm wastes are commonly fed to fish often
cultured in flooded rice paddies or for vegetable-fish culture.
The promise of modern agriculture However, one of the first successful commercial aquaponic
systems was established at the University of Virgin Islands
However, many agro-businessmen in the country never lose where several trials for vegetables production were
hope and still believe that agriculture is the only way to conducted using tilapia culture (Rakocy, 1989).
recover the country’s economy and pay its foreign debt (De As far back as 1150-1130 CE, chinampas, often referred to
Leon, 1995). Policy-makers in the country believe that by as "floating gardens”, were documented as the signs of
using climate-smart farming methods the food requirement sustainable agricultural systems (Pennington, 2011). Used
of the population can be met (Sace et al., 2008). This is in extensively by the American nomadic tribe, the gardens were
accordance with the optimistic prediction of the United established when their neighbors treated them roughly and
Nations Food and Agriculture Organization (FAO) of an drove them onto the marshy shore of Lake Tenochtitlan of
abundant world food supply in the coming years. The the great central valley of what is now Mexico. The Aztecs,
prediction is based solely on the availability of today’s denied of arable land, survived by building rafts of branches
technical knowledge that is capable of increasing agricultural and stems called chinampas and piling soil dredged up from
productivity (FAO, 2011) even in the face of an ever- the shallow bottom of the lake (Rahman, 1994). The Aztecs
increasing population, a decreasing land resource, less abundantly grew vegetables, flowers, and even trees on the
funding support and unpredictable and catastrophic climate rafts, with roots of these plants pushing down towards the
(Dolan, 1991; Zoe, 2011). This technical expertise will prove source of water. The Aztecs later defeated and conquered by
that scientific knowledge combined with computerized force of arms the peoples who had once oppressed them. The
equipment is more critical than hard work and muscle power chinampas, which were designed in a risk to stave off hunger,
that traditional agriculture customarily requires (Murphy, flourished to keep pace with the requirements of the capital
1984). city of Central Mexico. They never abandoned the lake,
Accordingly, the Department of Agriculture cited that one despite their empire grew bigger and became a huge,
potential solution to the problem of food shortage due to magnificent city.
climate change is ensuring self-sufficiency in food (Cayabyab, The world is so different now, and it is confronted with
2012). One strategy to bolster agricultural production is to more formidable problems than the Aztecs. Man need to be
cultivate, process, and distribute food in or around villages, witty and resilient to survive. Using climate-smart
towns and cities (Dumlao, 2012). This practice, called urban techniques, scientists and policy-makers have to work to
agriculture, is a type of small scale farming that could give chart a course that will ensure food security and create a safe
households, not only in the countryside, but also those in the operating space for farmers and food producers. Without
urban areas, additional income and significant access to exhausting earth’s limited resources, research and
affordable food from their own backyard. An alternative to development ventures are imperative to hone today‘s
intensive farming, it considers agriculture’s dependence on production systems for the next generation. Amidst the
finite resources such as land and water (Connolly and Trebic, threats of climate change, technologies like chinampas need
2010). One way to do this is to promote a production system to be promoted in order to sustainably produce more food.
known as aquaponics. This study was aimed at evaluating the growth and yield of
Aquaponics is a type of urban agriculture, a portmanteau of three leafy vegetables in recirculating aquaponic system
two different cultures: aquaculture or raising fish, and using tilapia and freshwater prawn poly-culture in controlled
hydroponics or crop production in soilless culture. environment.
Aquaponics (pronounced: /ˈækwəˈpɒnɨks/) has the benefits
of spending less money on fish and vegetables, and no money
on fertilizer. In this system, the nutrient-rich water that LITERATURE REVIEW
results from raising fish provides a source of natural fertilizer
for the growing plants. The plants help purify the water as A recirculating raft system was constructed for vegetable and
they consume the nutrients where the aquacultural crops live prawn production in a raceway using tank culture of tilapia.
in (Roe and Midmore, 2008). Computerized controls that automatically govern cooling
fans, heater and ceiling fan, optimum environmental
parameters like temperature and relative humidity inside the
History of aquaponics greenhouse were checked if properly functioning. Water
quality parameters were manually monitored using hand-
Historically, the first example of aquaponics was believed by held meters to attain a compromised ecosystem for vegeta-
Academia Journal of Agricultural Research; Sace and Fitzsimmons. 238

bles, prawn, tilapia and beneficial bacteria. Twenty-two kilograms of mixed-sex Nile tilapia (Oreochromis
To achieve the set objectives, major activities were niloticus) with an average weight of 150 g were stocked a
undertaken in an input-process-output concept as reflected week later (September 16, 2011) in each of the fish tanks.
in Figure 1. The density was based from the result of Licameli et al.
(2010) of 5 kg/m3 of tilapia and total volume of culture water
in the system. Likewise, 295 heads of juvenile freshwater
System design prawns (Macrobrachium rosenbergii) average weight of 1.66
g and average length of about 4.3 cm were stocked under the
Two recirculating aquaponic systems with a bio-filtration rafts in one of the systems. The other system, which was the
tank (Figure 2a), fish tank (Figure 2b) and a raceway (Figure control, contained no prawn. In a week time, 13 pcs of tilapia
2c) interconnected by PVC pipes to contain one body of water weighing approximately 2 kg have died in the system with
were constructed in a controlled environment greenhouse. prawn while 12 pcs of tilapia weighing less than 2 kg in the
The systems utilized a 40 W submersible pump to lift the system without prawn. The mortality was due mainly to
culture water from the 220 L bio-filtration tank to a 250 L handling stress. The same number and weight of fish were
fish tank and allowed to flow by gravity to a 4.41 L raceway added to each tank. For 30 days the systems were kept
in a closed loop. The systems were active-type polycultures running to allow the growth of algae and bacteria.
which maintained a water depth enough to keep Styrofoam F1 seeds of lettuce (Brassica rapa: Black-seeded Simpsom
rafts to float. The systems were installed in a gable-roofed variety), Chinese cabbage (Brassica rapa pekinensis), and pac
conventional greenhouse made of double-layered choi (Brassica rapa) hydroponically germinated in rockwool
polycarbonate sheets containing air spaces that acted as blocks and enhanced for one week with foliar fertilizer.
insulators. With side walls made of bricks, the structure Seedlings were plugged into the holes of the rafts (October
allowed good transmission of light. The greenhouse was 17, 2011) with 15 cm off-center spacing. These vegetables
equipped with environmental control systems with sensors were replicated five times in order to maximize the floor area
connected to a computer to record air temperature, relative of the raceway. With this, each experimental unit had 33
humidity and photosynthetically active radiation (PAR). plants or165 plants per treatment to contain 495 plants in
Cooling and heating devices included an overhead heater, the raceway for three treatments. No inorganic fertilizer or
two cooling fans, and a ceiling fan maintained the pre-set chemicals were added to the systems. Tilapia was fed with
optimum environmental conditions for the normal growth of commercial feeds ad libitum using 12 h belt feeder while
vegetables, prawn, fish and the beneficial bacteria. prawn relied on the scraps and undigested feed that enters
the raceway.
Seeds for the second crop of vegetables were propagated a
The Nitrogen cycle week before harvesting using the same procedure and
technique of germination applied in the first crop. A sample
Each structure has three essential elements: fish, bacteria of culture water from each raceway was sent to a reputable
and plants (Malcolm, 2007). As part of a fish’s normal protein laboratory for complete water analysis to determine pH, TDS,
digestion, ammonia is given off through their gills and urine nitrite, nitrate, potassium, phosphorus, calcium, magnesium,
of the fish, including any wastes or uneaten food. The wastes iron and other elements after each harvest. The analysis will
break down in the fish tank and quickly build up in the water be used as supplemental data to compare the two systems.
affecting the growth of fish. Two main types of bacteria carry
out the essential work. Nitrosomonas species digest ammonia
and convert it into nitrites while the Nitrobacter species then Data gathered
convert the nitrites into nitrates which can now be consumed
by plants (Rakocy et al., 2006). The fish and prawns are less The experiment was a comparative study of two systems
vulnerable to high levels of nitrites in the water though most which aimed to evaluate the productivity of three leafy
plants cannot absorb nitrites. The water flow back to the fish vegetables in an aquaponic system. The first system has
tank cleaned of excess nutrients and freshly oxygenated as tilapia-prawn culture as the independent variable and the
demonstrated in Figure 3. There is nothing artificial or three vegetables as the dependent variables while the second
unhealthy with these bacteria for they are completely natural system has tilapia as the independent variable and the
and beneficial (Nelson, 2008). vegetables as the dependent variable. It was completed in a
108 day culture period with two 35 day growing seasons of
vegetables planted in the system with prawn and in the
Management practices system without prawn. A set of data were collected every
harvest for each system. The average biomass and average
The systems were filled with tap water (September 11, 2011) dry weight of the vegetables were gathered to evaluate the
and were kept running for one week before stocking the fish. growth of the vegetables while fresh weight of leaves was
This was tocheck the systems for leaks andvolatilize chlorine used to evaluate the yield. Six plants were taken to represent
Academia Journal of Agricultural Research; Sace and Fitzsimmons. 239

Figure 1. The conceptual framework.

Figure 2. (a) The bio-filtration tank, (b) fish tank and (c) the raceway.

an experimental unit. Plants were carefully removed from the first and second harvest of vegetables. Feed conversion ratio
rafts as roots were entangled with the roots of other plants. was also computed. Likewise, the total water consumption of
Weight was determined using a digital weighing scale. the systems was determined by adding the daily evaporation
Samples were oven dried for 48 h at 80°C. Data were losses since the onset of the experiment with the total
carefully recorded, and statistically analyzed and interpreted volume of water in the system.
using single-factor Analysis of Variance (ANOVA). Similarly,
10 samples of tilapia and prawn were caught to determine
the growth and gain weight of aquacultural crops. Increase in RESULTS AND DISCUSSION
length was determined from head to the end of the tail based
from initial and previous measurements while gain in weight System performance
of tilapia and prawn was computed by subtracting the initial
weight from the final weight. These were done during the The design of the aquaponic systems followed the “one-pump
Academia Journal of Agricultural Research; Sace and Fitzsimmons. 240

Figure 3. The Nitrogen cycle.

rule”: the culture water must be recirculated by one pump
starting from the lowest point and allowing the system to
flow by gravity in a close loop. The rule was given by a wise
man and former owner of Seagreenbio in Palms Spring,
California, USA, Mr. Dean Farrel, who claimed that systems
designed in this way saved energy and aggravation (Rakocy
et al., 2006). That is why both systems were operated by one
pump submerged in the bio-filtration tank, the lowest point,
to raise the culture water to the fish tank, the highest point,
and allowed to flow by gravity through the raceway and back
to the bio-filtration tank.
During the course of time conducting the experiment, it was
experienced that system failure is possible if a filter in the
stand pipe at the exit of water in the raceway is improperly
designed. The filter is necessary to prevent the prawn from
escaping and find their way to the bio-filtration tank. The
possibility that clogging the filter (Figure 4a) can occur is not
far as roots and other debris blocked the filter. In addition,
the vortex of water coming out of the raceways can
eventually create a sucking pressure on the raft, preventing
water to flow. The weight of the vegetables and roots as they
hang on the raft adds up to the problem. Hence, a perforated Figure 4. (a) Fabricated stand pipe filter made from
discarded cup and (b) perforated PVC pipe.
pipe (Figure 4b) was fabricated to allow water to flow freely

and efficiently recirculate in the system. Several holes on the

pipe allowed the flow without restraint.
The temperatures of the culture water dropped below the system raised the temperature. In addition, the thermal
desired level during the advent of winter. The installation of energy absorbed by the culture water in the fish tank,
two 300 W water heaters in the bio-filtration tank in each raceway, and bio-filtration tank during the day with sunlight
Academia Journal of Agricultural Research; Sace and Fitzsimmons. 241

aided in maintaining the water temperature and balanced the Tank-bed ratio
effects of low night time temperature to an average of 21.2°C.
The installation of a water heater in the bio-filtration tanks The tank bed ratio, also known as component ratio, used in
created a factor of safety for the living organism from this experiment was based on the conclusion made by
overheating. An excessively high temperature that would kill Licameli et al. (2010) in a study to evaluate the optimal
the fish is possible scenario when pump failure or power stocking density of tilapia for lettuce production. A density of
outage if heaters were installed in the fish tank. 5 kg of fish per m3 of culture water resulted in 22 kg of Nile
In the same way, DO levels are normally fluctuated as water tilapia for the total volume of water of 4.40 m3 in the system
flowed along the four observation stations in the systems. DO including the bio-filtration tank. This volume was later
level in the system with prawn in the fish tanks was normally decreased to 2.85 m3 when the depth of water in the raceway
the lowest at 3.8 ppm. This was because most of the excretion was reduced from 33 to 20 cm without changing the stocking
of tilapia was produced in the fish tank. This level increased density of fish. This was done to increase the concentration of
to 5.9 ppm at the entrance in the raceway and further nutrients produced by the fish in the system as a remedy to
increased to 6.7 ppm at the exit in the raceway. The highest nutrient deficiencies manifested in the plants leaves. At this
values of DO happened in the raceway because water was depth, the volume of water in the raceway becomes 2.38 m3.
highly aerated. Plant roots also added oxygen as part of With a fish tank volume of 0.25 m3, the component ratio
respiration. DO slightly decrease to 6.2 ppm in the bio- therefore becomes 1:9.5. In comparison, a fish tank: grow
filtration tank. In the system without prawn, the average DO bed ratio of 1:1 as used in early systems or 1:2 that is now
in the fish tank was 4.2 ppm then fluctuated to 5.6, 6.3, and common or as high as 1:4 that others growers try to intensify,
6.3 in the entrance and exit of the raceway and in the bio- are acceptable. The ratio 1:9.5 maybe an exaggeration and
filtration, respectively. These values were within the was far too big for growing vegetables. With this ratio, there
recommended limits (Rakocy et al., 2006). was no doubt that plants were chlorotic and necrotic. In
The design of the raceway, being rectangular, has poor flow addition, the Speraneo system, for example, is designed for a
characteristics. Although easier to construct, the incoming component ratio of 1:2 using pea gravel as growing bed
water flowed directly to the drain short-circuiting the tank. media. This means that a fish tank of 0.25 m3 requires a
Waste and organic matter accumulated in some part of the volume of 0.50 m3 in the raceway. This also proves true that
raceway while other areas remained stagnant with pockets of component ratio is another crucial factor in designing
lower oxygen levels. This was one of the disadvantages of aquaponics which therefore can devastate production or can
having a rectangular raceway as compared to circular design favor greater outputs (Diver, 2006).
that could create a current to collect the organic matter to the
centre and out to the drain.
Environmental monitoring parameters

Stocking density The real-time data of environmental factors that were logged
at 5 min interval was extracted from the computer. Air
According to Rakocy (1989), intensive tank culture can temperature, relative humidity and PAR were processed by
produce a very high yield of tilapia by stocking 50‒100 g taking the average values of the day and the night readings
tilapia at a rate of 100‒200 fish per m3 of culture water or based on Julian day.
even as high as 250 fish per m3. At this rate, 5‒20 kg of fish A compromised environmental condition crucial for
or even as high as 25 kg is possible to be reared in a cubic production of tilapia, prawn, vegetables, and for optimal
meter of culture water provided that a higher degree of activity of nitrifying bacteria in the system (Tyson, 2007),
environmental control over parameters is provided by was maintained. Data was then tabulated compared to the
aeration and frequent or continuous water exchange. This is compromised environmental conditions and tabulated in
to renew dissolved oxygen supplies, and remove waste and Table 1.
increase the growth of beneficial bacteria in the system. Air temperature and relative humidity inside the
Using these proven facts to compare the stocking density greenhouse were maintained at 22‒30°C and 40‒90%,
used in the experiment, stocking as many as 71 fish with an respectively. pH was maintained at 6.0‒7.5, water
initial average weight of 150 g and final average weight of temperature at >20.0‒30.0°C, TDS at >300 ppm and
309.9 g in a 0.25 m3 tank was far too high a stocking density dissolved oxygen at >3.0‒8.0 ppm with minimum saturation
that corresponded to 42 kg/m3. This condition had resulted of 60%.
in a slower growth rate. With this stocking density, DO was Day and night temperatures were pre-set at 22-30°C with
low and fish had less space to swim around and finding food the aide of overhead heater, cooling fans and ceiling fans.
became difficult. This indicated that the volume of the fish However, the two systems were subjected to fluctuations of
tank was inadequately matched with the stocking density. outside temperature that created variations in the interior
This means that stocking density is one of the fundamental environment conditions of the greenhouse by approximately
considerations in designing aquaponic system. ±2°C during the first cropping season (October 11 to Novem-
Academia Journal of Agricultural Research; Sace and Fitzsimmons. 242

ber 11, 2011). At these air temperature ranges, relative when level is too high or too low (Anderson et al., 1989).
humidity correspondingly fluctuated from 55‒85%. The A TDS of 525‒1,400 ppm was aimed as ideal although
second cropping season was slightly colder than the last these nutrient levels are difficult to attain in aquaponics.
growing season, with air temperature mildly dropped to During the two cropping seasons, the system with prawn
20‒28°C while relative humidity rose from 58‒87%. These achieved only a TDS of 246‒393 ppm while 228‒344 ppm for
fluctuations were the effects of low night temperature during the system without prawn. Lettuce requires a TDS ranging
the winter season, though ideally, the relative humidity of the from 560‒840 ppm while the requirements of cabbage and
air surrounding plants should be maintained around 70% at pac choi are 1,750‒2,100 and 1,050‒1400 ppm, respectively,
night and 85% during the day (Rorabaugh, 2011). On the as presented in Table 3. Thus, vegetables showed various
same hand, PAR also changed from 435‒685 nm during the deficiencies.
first cropping season to 410‒645 nm during the second Water temperature of the two systems was also affected by
cropping, both within the range of the crop requirement. PAR the advent of winter. Temperature during the two cropping
is normally between 400‒700 nm, but the quantity was seasons ranged from 17‒24°C while 19‒24°C for the system
gradually reduced after the equinox (September 23, 2011). without prawn. The lower values of the range were below the
According to Rorabaugh (2011), crop production in Tucson, optimum desired temperature of 20‒30°C. At these range,
Arizona is affected by both day length and angle of the sun as the water is warm enough to stimulate good growth rates but
season changes. On June 21 for example, the day length is 14 at the same time cool enough to carry maximum oxygen
h and 15 min as compared to December 21 with only about content for all species in the system including the bacteria
10 h. The quality and quantity of light directly affected plant (Carruthers, 2002; Connolly and Trebic, 2011; New, 2002).
growth which gives an indication of the possible amount of
photosynthesis and growth being performed by the plant.
Increasing energy in the PAR range increases plant Laboratory analysis
photosynthesis (Rorabaugh, 2011).
Water samples taken from the center of the each raceway
after the first harvest of vegetables and analyzed by a
reputed agricultural laboratory for water analyses,
Water quality monitoring parameters
substantiated the data collected daily. Results (Table 4)

confirmed that the pH in the two raceways was above the
Water quality monitoring parameters like pH, TDS,
recommended levels for vegetables and were appropriate for
temperature, dissolved oxygen and saturation were targeted
the aquacultural crops with 7.5 in the system with prawn and
to attain a compromised ecosystem that was desirable for the
7.8 in the system without prawn. Consequently, TDS in both
living organisms in the systems. Values to create a
systems was far below the requirement of the three
compromised habitat and the levels achieved by the systems
vegetables with 311 ppm and 292 ppm in the system with
were presented in Table 2.
and without prawn, respectively. Further, the analyses also
A desirable pH ranging from 6.0‒7.5 was anticipated since
revealed that the system with prawn contained higher
pH is a major limiting factor in aquaponics, any system that
amount of nitrogen, nitrate nitrogen, sulfates, calcium,
can achieve with optimal pH for the aquacultural crops, the
magnesium, sodium, chlorides, iron, phosphates, manganese
hydroponic crops and the bacteria are usually productive
and hardness as compared to system without prawn. No
(Tyson, 2007). pH higher than this range will be detrimental
wonder plants in the system with prawn were heavier,
to plants (Anderson et al., 1989) although beneficial to
greener and taller than those planted in the system without
tilapia, prawn and the bacteria grow best at this level
prawn. Although nutrient deficiencies were both seen in
(Rakocy et al., 2006). Religious monitoring was done daily
plants in both systems, plants in the system without prawn
early in the morning when the sun was not yet set, the best
had more obvious signs and appeared more chlorotic and
time to collect data since photosynthesis stops at night while
necrotic while lettuce had elongated stalks as depicted in
respiration continues (Francis-Floyd, 2011). Fish, prawn and
Figure 5. Deficiency symptoms were highly noticeable in
bacteria prefer a pH 7.0‒9.0 since and most plants grow
Chinese cabbage so that its eating quality was poor.
within 5.8‒6.8 and must be maintained at the desired level.

However, the systems found difficulty in achieving the
desired requirements. A hand-held pH-TDS-temperature
meter was used to measure the parameters. The system with Growth of vegetables
prawn developed a pH of 6.5‒7.5 during the first cropping
season and 7.1‒7.9 during the second cropping while the The vegetables were harvested 35 days after seeding (Figure
system without prawn achieved a pH slightly higher than the 6). The growth of vegetables was determined using the total
system with prawn and the desired level during the first biomass and total dry weight of the vegetables. Biomass is
cropping ranging from 6.7‒7.7 and 7.3‒8.2 during the second the material produced by photosynthesis in which the energy
cropping season. A pH higher than 8 can prevent plants to from the sun converts carbon dioxide and water to
absorbed the nutrients which results to deficiency or toxicity carbohydrates and oxygen. This includes the roots and the
Academia Journal of Agricultural Research; Sace and Fitzsimmons. 243

Table 1. Compromised and achieved levels of environmental monitoring parameters of the systems.

Level achieved by the system
Parameter Compromise level* With Prawn Without Prawn
1st crop 2nd crop 1st crop 2nd crop
Air temperature (°C) 22-30 22-30±2 20-28±2 22-30±2 20-28±2
Relative humidity (%) 40-90 55-85 58-87 55-85 58-87
PAR (nm) 400-700 435-685 410-645 435-685 410-645

* Values compiled from various literatures.

Table 2. Compromised and achieved levels of water quality monitoring parameters achieved of the system.

Level achieved by the system
Parameter Compromise level* With Prawn Without Prawn
1st crop 2nd crop 1st crop 2nd crop
pH 6.0-7.5 6.5-7.5 7.1-7.9 6.7-7.7 7.3-8.2
Total dissolved solid (ppm) >300 246-344 240-393 228-328 261-344
Water temperature (°C) >20.0-30.0 18.8-22.9 16.3-23.5 19.2-23.9 18.5-24
Dissolved oxygen (ppm) >3.0-7.0 3.2-6.9 2.8-7.3 3.2-6.7 3.0-7.2
Saturation (%) >60 58-125 51-123 52-123 26-127

*Values compiled from various literatures.

Table 3. pH and TDS requirements of lettuce, Chinese cabbage and pacchoi.

Vegetables pH Total dissolved solid (ppm)
Lettuce 5.5-6.5 560-840
Chinese cabbage 6.5-7.0 1750-2100
Pac choi 7.0 1050-1400

leaves of the plants. temperature during the height of winter caused the
As tabulated in Table 5 and depicted in Figure 7, the total temperature drop. Plant roots function best at temperature
biomass of lettuce, Chinese cabbage and pac choi grown in range between 18‒22°C.
the system with prawn was heavier than those grown in the The total dry matter was summarized in Table 6 and
other system during the first harvest having total of 86.6, shown in Figure 8. The total dry matter of vegetables in the
179.5 and 185.2 g, respectively. Those that were planted in system with prawn during the first harvest was heavier than
the system without prawn weighed 86.2, 163.3 and 172.9 g, those in the system without prawn having averages for
respectively. A similar pattern happened during the second lettuce, Chinese cabbage and pac choi of 4.9, 7.1 and 7.7 g,
harvest when lettuce, Chinese cabbage and pac choi that respectively, while the total dry matter in the system without
were grown in the system with prawn were heavier than prawn were 4.9, 6.5 and 7.2 g, respectively. The same trend
those plants grown in the other system with averages of 84.6, occurred during the second harvest, with averages in the
168.5 and 190.0 g, respectively. Those that were planted in system with prawn heavier than the system without prawn.
the system with prawn weighed 80.9, 165.7 and 178.3 g, The total dry matter in the system with prawn were 3.8, 6.8
respectively. and 7.2 g for lettuce, Chinese cabbage and pac choi,
ANOVA revealed no significant differences among the respectively while 3.6, 6.1 and 6.3 g in the system with
means of total biomass of lettuce and Chinese cabbage grown prawn, respectively.
in systems with and without prawn during the first and ANOVA on the means of total dry matter of lettuce revealed
second harvest. However, there were significant differences no significant differences during the first and second
among the means of the total biomass of pac choi during the harvests. This means that lettuce in both systems contained
first and second harvest. Harvest in the system with prawn the same amount of dry matter. Lettuce is less tolerant to
was better than the system without prawn during the first high pH in both systems which were higher than the desired
and second harvest. The combined effects of low pH, low TDS value. However, there were significant differences in the
and low temperature the vegetables with greater effects of means of total dry matter of Chinese cabbage and pac choi
Academia Journal of Agricultural Research; Sace and Fitzsimmons. 244

Table 4. Laboratory analysis of culture water in systems with and without prawn.

Parts per million USEPA Guidelines
Items
With Prawn Without Prawn
Nitrogen 30.8 24.6 NO3= 25 ppm
Nitrate Nitrogen 7 5.6 N= 100 ppm
Sulfates 41 36 250 ppm
pH 7.5 7.8 6.5-8.6 secondary std
Calcium 180(10.5 g/gal) 155(9.1 g/gal)
Magnesium 45(2.6 g/gal) 35(2.0 g/gal)
Sodium 48 46 ppm
Chlorides 70 68 250 ppm
Total dissolved solid (ppm) 311 292 500 ppm secondary std
Hardness 225(13.1 g/gal) 190(11.1 g/gal)
Total iron 0.5 0.1 0.3 ppm secondary std
Phosphates 25 19.75
Phosphorus 8.3 6.58 0.400 ppm secondary std
E.coliform N/A N/A <1/100 ml
Total coliform N/A N/A <1/100 ml
Copper N/A N/A 1 ppm secondary std
Zinc N/A N/A 5 ppm secondary std
Manganese 0.07 0.038 0.05 ppm secondary std
potassium N/A N/A
Comments N/A N/A

Figure 5. (a) The elongated leaves of lettuce, (b) chlorotic and necrotic leaves of Chinese cabbage and (c) pacchoi.

during the first and second harvests. This was because Yield of vegetables
Chinese cabbage and pac choi in the system without prawn
suffered from nutrient deficiencies that led to chlorosis and The fresh weight of leaves was referred to as yield and was
necrosis having lesser amount of nutrients than the system presented in Table 7 and depicted in Figure 9. The yields of
without prawn. lettuce grown in the two systems during the first and second
The results also revealed that the total dry matter only harvests were almost identical. During the first harvest of
represented fraction of the average biomass of the vegetables, each lettuce plant grown in the system with
vegetables. The biggest average dry matter occurred in the prawn had an average weight of 77.5 g while 78.5 g for each
system with prawn. Lettuce has 5.7% occurring during the lettuce from the system without prawn. During the second
first harvest, 6.8% for Chinese cabbage and 7.2% for pacchoi harvest, each lettuce plant grown in the system with prawn
both during the second harvest. This also means that more weighed an average of 75.5 g while those that were grown in
than 90% of the biomass of the vegetables was water. the system without prawn had an average of 73.1 g. This
Academia Journal of Agricultural Research; Sace and Fitzsimmons. 245

Figure 6. The lettuce, Chinese cabbage and pacchoi in systems with prawn, (a) and without prawn ready for harvest

Table 5. Total biomass of vegetables (g) in systems with and without prawn.

With Prawn Without Prawn
Vegetables
1st crop 2nd crop 1st crop 2nd crop
Lettuce 86.6 84.6 86.2 7.3-8.2
Chinese cabbage 179.5 168.5 163.3 165.7
Pac choi 185.2 190.0 1172.9 178.3

Figure 7. The total biomass of lettuce, Chinese cabbage and pacchoi grown in systems with and without prawn during the first and second harvests.

average yield per plant was lowest compared to those of first and second harvests. Similarly, pac choi had good yield
Chinese cabbage and pac choi. Each Chinese cabbage plant during the first and second harvests averaging 167.9 and
grown in the system with prawn yielded an average weight of 171.0 g per plant when grown in the system with prawn and
166.6 and 154.2 g during the first and second harvests, 155.9 and 161.2 g, respectively.
respectively. When grown in the system without prawn, each ANOVA revealed no significant differences among the
Chinese cabbage plant yielded 153.5 and 151.7 g during the means of yield of lettuce and Chinese cabbage both grown in