| Summary: | 碩士 === 國立成功大學 === 工程科學系 === 103 === SUMMARY
The primary research purpose of this study is to promote the environmental protection by the aquaponics system using different designs with the LED light source, natural light, and water flows on growth for culturing different plants. Experiments included three different irrigation water cycle systems, Overflow A system, Overflow B system, and Floating Raft system. Experimental results revealed that with the conditions of LED light intensity being fixed to 210 μmole･m-2･s-1 and of adding wastewater of Earthworm for fertilization, both basil and ettuce grow well in the Overflow A and B system. Similarly, Chinese cabbage, lettuce, water spinach, basil, Chrysanthemum, and rape grow successfully in the B overflow systems.
In the Floating Raft system with natural light, however, the growing situation is not good due to insufficient nutrients, even though plant roots grow better than those by the LED light source.
Keywords: Aquaponics System, Overflow, Floating Raft, light-emitting diode, earthworm.
INTRODUCTION
The study is motivated by the green awareness of society. The traditional agricultural irrigation contains a large amount of nitrogen fertilizer with phosphorus which can cause pollution of nearby lakes. It also consumes a large amount of water. In contrast, the ebb-and-flow system irrigation for plant cultivation can reduce 50% to 65 % usage of pesticides, 85% of wastewater, and 50% usage of chemical fertilizers. Further, by combining fish and plant production together in an integrated recirculating system, referred to as aquaponics system, can effectively improve the utilization efficiency of water and reduce the usage of fertilizers and pesticides.
Therefore, we designed three different recirculating irrigation systems for the aqauponics, using light-emitting diodes and natural light as the light sources, to evaluate theirs merits.
MATERIALS AND METHODS
All components are bought from the general stores. For the three systems, the first one is for comparing the effect of different LED light sources and water quality on the plant growth of the aquaponic system. The second one is for comparing the effect of different water quality on the plant growth of the aquaponic, using single type LED light source. The third one is for exploring the effect of natural light and different water quality on the plant growth of the aquaponic system. The features of the three different lights source are Y-LED light (intensity of 210 μmole･m-2･s-1), W-LED light (intensity of 210 μmole･m-2･s-1), and natural light. The Y LED and W LED are different light qualities but same micromole.
Three irrigation methods include overflow A system, overflow B system, and floating raft system. Water pump supplies automated water circulation in which the water level is adjusted growth of different irrigation methods on plants.
The overflow A system has a total of six experimental groups with Tilapia polyculture Macrobrachium rosenbergii, the overflow B system has a total of three experimental groups with Comet goldfish polyculture Colored skirt tetra and Tetra Xiphophorus maculatus, the floating raft system has a total of two experimental groups with Cyprinus carpio.
The plant cultivation period is from five to eight weeks. During the period, the water quality is sampled every seven days to monitor pH (PH5011, EZDO, Taiwan) and electrical current (EC) (EC5061, EZDO, Taiwan), Ammonia (NH3-N) (Fresh water master test kit, API, US), Nitrite Nitrogen (NO_2^( -)-N) (Fresh water master test kit, API, US), Nitrate Nitrogen (NO_3^( -)-N) (Fresh water master test kit, API, US); every month the measurements of Ammonia, Nitrite Nitrogen, Nitrate Nitrogen are verified by U2001 (Hitachi, Japan) to assure the water quality. Furthermore the water quality is sampled each month and monitored for Dissolved Oxygen (DO) (YSI5000,YSI, US), Calcium (Ca) (Z8200,Hitachi, Japan), Carbon (C) ( 1010 TOC Analyzer, OI Analytical's, US), and Iron (Fe) (Z8200,Hitachi, US). The dry weight and nitrate concentration (U2001, Hitachi, Japan) of the plants are measured at the end of each experiment.
RESULTS AND DISCUSSION
Overflow A system is set up in an indoor environment and has six experimental groups. The results of plant growth and water quality are as follows.
1. Period of Initial system
After eight weeks of cultivating time, all plants can not grow effectively due to low EC of around 0.3~1.0 mS/cm in the aquaponic system, even though with adequate lighting. The water pH of water is around 7.8~8.3.
2. EC and number of fish
The use of increased eight Tilapia were upgrade to EC, After five weeks cultivating time, the results showed that all plants could not effectively grow due to pH is too high, resulting in nutrients can not be dissolved in water, even though enough adequate lighting. In the case of a water quality parameter, pH of water is around 8.1~7.9 and EC of water was around 1.2~1.7 mS/cm in the aquaponic system.
3. pH and Nitrification
By nitrification to reduce pH, after six weeks of cultivating time, all plants still can not grow effectively even though enough adequate lighting due to LED light quality and plant types as different plants require different light quality and nutrients. The water pH is around 7.2~7.8 while EC is around 1.7~1.9 mS/cm in the aquaponic system. NH3-N of water is around 8~4 mg/L, NO_2^( -)-N around 2~1.44 mg/L, and NO_3^( -)-N of water around 80~116 mg/L in the aquaponic system.
4. Different LED light source and plant species
By using different LEDs and by cultivating many types of plants, after five weeks of cultivating time, all plants still can not grow effectively grow due to competition of nutrients, even though with adequate lighting. The pH of water is around 7.1~7.4, EC around 1.8~1.5 mS/cm, DO being 7.0 mg/L, NH3-N around 0.25~1.79 mg/L, NO_2^( -)-N around 0.5~1 mg/L, and NO_3^( -)-N around 80~74 mg/L in the aquaponic system.
5. Reduce plant density
Reducing the number of plants and after five weeks of cultivating time, all plants can not grow effectively due to lack of iron and calcium, even though enough adequate lighting. The pH of water is around 7.2~7.5, EC around 1.5~1.4 mS/cm, Fe being 0 mg/L, Ca being 31.5 mg/L, NH3-N around 0.5~0.25 mg/L, NO_2^( -)-N around 2~1 mg/L, and NO_3^( -)-N around 80~45 mg/L in the aquaponic system.
6. Use Earthworm wastewater to grow plants successfully
Adding Earthworm wastewater to the plants at night and after eight weeks of cultivating time, Lettuce and Basil grow effectively grow as Earthworms wastewater contains enough Iron and Calcium. The pH of water is around 7.2~7.4, EC around 1.8~1.5 mS/cm, C (?) being 0 mg/L, NH3-N around 0.25~1 mg/L, NO_2^( -)-N around 1~0.5 mg/L and NO_3^( -)-N around 40~69.7 mg/L in the aquaponic system.
Overflow B system has three experimental groups and the results are as follows.
1. Period of initial system
After seven weeks of cultivating time, except Chinese cabbage, other plants can not grow effectively due to lack of iron and calcium, even though enough adequate lighting. The pH of water is around 8.3~7.8, EC 0.3~1.0 mS/cm, NH3-N 8~0.25 mg/L, NO_2^( -)-N around 14.91~0.25 mg/L and NO_3^( -)-N around 20~80 mg/L in the aquaponic system.
2. Use earthworm wastewater to grow plants successfully
By adding earthworm wastewater to the plants at night, after eight weeks of cultivating time, Lettuce, Chinese cabbage, Garland chrysanthemum, Water spinach, and Basil grow effectively. The pH of water is around 6.8~6.9, EC around 1.0~0.9 mS/cm, Fe being 0 mg/L (?) and Ca being 31.8mg/L, NH3-N around 0.2~1 mg/L, NO_2^( -)-N around 2~1mg/L and NO_3^( -)-N around 34.2~40mg/L in the aquaponic system.
3. Use earthworm wastewater to grow plants successfully
By adding earthworm wastewater at night and after eight weeks of cultivating time, Cole, Water spinach and Lettuce grow effectively. the pH of water is around 6.8~6.7 and EC around 1.0~0.9 mS/cm, Fe being 0 mg/L, Ca being 10.69 mg/L, NH3-N around 1.15~0.25 mg/L, NO_2^( -)-N around 0.25~0.5mg/L, and NO_3^( -)-N around 23.26~80 mg/L in the aquaponic system.
Floating raft system has two experimental groups for the plant growth as follows.
1. Period of Initial system
In the outdoor environment with natural light, after five weeks of cultivating time, the results show that plants can not grow effectively due to nutrient deficiencies in the water, even though enough adequate lighting. The pH of water is around 8.8~8.6, EC around 0.3~0.5 mS/cm, Fe being 0.13 mg/L, Ca being 12.57 mg/L, NH3-N around 0.25 mg/L, NO_2^( -)-N around 0.25~0.24 mg/L, and NO_3^( -)-N around 10~20 mg/L in the aquaponic system.
2. Light shielding in water spinach
By partially shielding the natural light, after five weeks of cultivating time, the plants can not grow effectively due to nutrient deficiency as described above. The pH of water is around 8.6~8.8, EC around 0.5~0.4 mS/cm, Fe being 0.12mg/L, Ca being 6.50 mg/L, NH3-N around 0.25~0.1 mg/L, NO_2^( -)-N around 0.25~0.01 mg/L, and NO_3^( -)-N around 10~0.82mg/L in the aquaponic system.
CONCLUSION
The results show that earthworm wastewater and light intensity are important factors of growing plant in a recirculating aquaculture system. After testing, at least the light intensity needs to be 210 µmole･m-2･s-1 in order to make photosynthesis in Chinese cabbage, Lettuce, Basil, Chrysanthemum, and Water Spinach. Both overflow A and B circulating irrigation systems can provide enough oxygen content for Tilapia and goldfish for their successful living in the apuaponics system.
In addition, the nitrate concentration of the successfully cultivated plants meets the standard regulated by the European Commission No. 563/2002.
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