An evaluation of potential development of a catfish-lettuce aquaponic culture system | |
| Author | Sikawa, Daniel Clement |
| Call Number | AIT Diss. no.AQ-10-01 |
| Subject(s) | Catfish fisheries Lettuce Aquaponics |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Aquaculture and Aquatic Re sources Management. |
| Publisher | Asian Institute of Technology |
| Abstract | This research was conducted to evaluate the potential for development of a catfish-lettuce hydroponic culture system. The research process included both a survey of commercial catfish farms and a series of experiments conducted at the Asian Institute of Technology. The field survey was conducted at the three commercial catfish farms in Pathumthani (two farms) and Ayutthaya (one farm) provinces in Thailand. The objectives were to determine the catfish culture practices and characterize pond water quality. At each farm, one pond was selected for sampling and analysis of pond water bi-weekly. A structured questionnaire was used to collect information about the culture systems of the farms. The farms were stocked with hybrid catfish (Clarias macrocephalus x Clarias gariepinus) at a rate of >62 fish m2. The results showed that homemade feed based on mixture of cassava roots (2.14 % Crude Protein; CP) and chicken offal/viscera (56.50 % CP) gave better yields than culture systems that used chicken manure supplemented with commercial pellet feed and kitchen refuse, however lowest food conversion ratio (FCR) was obtained from the latter. Water quality analysis showed that high feed and fertilizer input caused low concentrations of dissolved oxygen in the pond water. In order to maintain tolerable water quality for fish growth, catfish pond water was drained and re-filled with fresh water during the later stages of the culture cycle. There were four experiments. The first experiment consisted of a 2 x 3 factorial design with two filtration regimes (unfiltered versus filtered pond water) and three aggregates (Styrofoam control, sand, and gravel). The experiment was conducted for 54 days to investigate the potentials and constraints of the use of catfish pond water for the hydroponic lettuce (Lactuca sativa L) production, nutrient uptake and growth. The hydroponic units were placed on a bamboo platform across the pond surface. An earthen pond (226 m2) was stocked with 8,000 hybrid catfish with an average initial weight of 6.2 1.6 g and fish were fed with commercial pelleted feeds containing 30 % CP. Twenty-one-day old lettuce seedlings were transplanted in the hydroponic beds four months after stocking catfish in the pond. Pond water was partially filtered by using a settling tank and filtration tank which contained netting materials to trap solids. Lettuce plots were irrigated twice daily at 0800 and 1600 h using either filtered or unfiltered pond water for 45 minutes. The experimental results showed that the highest head weight and yield of lettuce were produced by plants grown on the sand media followed by gravel and the control treatments. Partially filtered pond water treatments gave significantly higher lettuce yield (P<0.05) than the rest and filtered water increased lettuce yield of the control, gravel and sand treatments by 87, 63 and 52 %, respectively, over unfiltered water treatments. Lettuce grown on gravel and the filtered-water control treatments had adequate tissue N content (30.82 ± 0.49 mg g-1 DW). The results showed that although there is a potential to use filtered and aerated catfish pond water for the hydroponic lettuce production, pond water is mainly constrained by the high suspended solid (42.56 ±3.64) and low dissolved oxygen (0.78± 0.28). The second experiment was conducted to investigate the effect of plant shading on nutrient uptake and growth of lettuce grown on sand as a hydroponics substrate using a completely randomized design (CRD). There were four treatments with three replicates. iv Treatments consisted hydroponic units without cover (control) and cover with a transparent polyethylene sheet, netting material, and a combination of netting material and transparent polyethylene sheet (the roof was covered with transparent plastic sheeting to protect the plants from rains and direct sunlight, while the sides were covered with netting material to improve air circulation and at the same time to prevent insects from having access to the plants). The results showed that the control treatment allowed the plants to receive higher photosynthetically active radiation (PAR; P< 0.05), while plants in the treatment covered with plastic received least PAR (P<0.05). The control had higher yields than the rest. Air temperature in the treatment covered with plastic was higher (P<0.05) than all other treatments. Content of nitrogen and phosphorous in lettuce plants was lowest in treatments shaded with plastic materials. There was a positive correlation between solar radiation and plant dry weight (r2 = 0.72) and a negative correlation between lettuce plant dry mass and temperature (r2 = 0.62). The optimum irrigation frequency for nutrient uptake and growth of hydroponically grown lettuce was investigated in the third experiment using a completely randomized design with three replicates per treatment. Five irrigation frequencies (treatments) were as follows; R1: 1 × day-1, R2: 2 × day-1, R3: 3 × day-1, R4: 4 × day-1, R5: 5 × day-1 and the duration was 45 minutes for each irrigation. The results showed that the frequency of irrigation significantly influenced (P<0.001) lettuce yields (fresh and dry weight), nitrogen and phosphorous uptake. N uptake of lettuce decreased with increase in irrigation frequency. The last experiment was conducted to evaluate the effect of supplementing nutrients in catfish pond water with commercial nutrient solution for lettuce and assessing the economic feasibility for integrating catfish culture with hydroponics vegetable production. Hoagland nutrient solution (complete strength) and three concentration levels namely 75, 50 and 25 % ionic concentrations were compared with catfish pond water. There were five treatments that were arranged in a completely randomized design with 3 replicates to the each treatment. The treatments were as follows; 100 % strength; 75 % strength; 50% strength; 25 % strength and catfish pond (control). The cost and return analysis was used to evaluate the economic feasibility. The results showed that the supplementation of catfish pond water with 25, 50 and 75 % nutrient solution increased yield by 27, 53 and 97%, respectively (FW). There was a positive correlation between electrical conductivity (EC mS cm-1) level and leaf yield of lettuce (FW), lettuce head weight and dry weight, r2 = 0.88, 0.82 and 0.86, respectively and uptake of leaf lettuce increased with increase in nutrient solution strength. Regression analysis showed positive correlation between nutrient strength and gross margin, r2 = 0.84. However there were no benefits in terms of dry matter yield when pond water was supplemented with nutrient solution of 25% strength. The current study showed the need for filtration of catfish pond water before using for hydroponics culture. Hydroponics units should not be irrigated frequently to counteract the low nutrient concentration of pond water. The shading of lettuce plants grown hydroponically decreased the yield and increases the investment cost. Catfish pond water is turbid and highly polluted. The utilization of 100% pond water is not economical in terms of income, but usage of it with supplementation of nutrients may provide options for reduction of the potential pollution that could arise from discharge of such waters. |
| Year | 2010 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Aquaculture and Aquatic Resources Management (AQ) |
| Chairperson(s) | Yakupitiyage, Amararatne |
| Examination Committee(s) | Ranamukhaarachchi, S.L.;Gallardo, Wenresti G.; |
| Scholarship Donor(s) | Icelandic International Development Agency , Malawi |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2010 |