| Author | Hassan, Md. Shafiqul |
| Call Number | AIT Diss. no.AE-90-02 |
| Subject(s) | Fish-culture
|
| Note | A dissertation submitted in the partial fulfillment of the requirements for the degree of Doctor of Technical Science, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. AE-90-02 |
| Abstract | A fertilization strategy was developed with synthetic nitrogen (N) and phosphorus (P) supplementation of low quality manure from small-scale farm cattle. Fertilization aimed at a balanced production of natural food organisms and the maintenance of a suitable environment for growth of Nile tilapia (Oreochromis niloticus). A series of four experiments were conducted in outdoor Sm2 static water concrete tanks, the design of each successive experiment was dependent upon the results of the preceding experiment. Experiment 1 was designed with a constant loading rate of manure but a variable rate of supplementation with synthetic N and P; Experiment 2 had a constant loading rate of manure but variable rations of N and P; Experiment 3 had a constant loading rate of total N and P but with variable manure and synthetic N and P loading rates; and Experiment 4 had constant loading rates of manure and synthetic N and P but had variable fertilization frequencies. Neither synthetic fertilizer nor cattle manure along gave satisfactory fish yield in comparison to a mixture of both. Fish growth in tanks fertilized with synthetic fertilizers was limited by high pH and high un-ionized ammonia-N concentration. Cattle manure alone was also unable to produce a good fish yield because of its relatively low nutrient content compared to manure from feedlot livestock; a loading rate as high as 400 kg dry matter/ha/day which provided relatively high levels of N and P, caused anaerobic conditions at dawn and led to low phytoplankton biomass due to its high biological oxygen demand. However, a fertilization regime with a mixture of manure and synthetic N and P was balanced in terms of water quality and fish growth. Variation in fertilization frequency did not affect fish growth and yield in a short-term tank experiment. However, it is suggested that fertilization should comprise an initial high dose to trigger algal growth, followed by frequent smaller doses to ensure a continuous supply of nutrients for algae. Mortality of tilapia was mainly caused by a high concentration of un-ionized ammonia-N(>1.0 mg/1), accompanied by high pH (>10.0) and low dawn dissolved oxygen (<1.0 mg/1). Tilapia were quite resistant to low dissolved oxygen and survived by gulping oxygen from the air-water interface, even when tanks were anaerobic at dawn, provided that the un-ionized ammonia-N concentration remained low. The best fertilization strategy obtained from the tank experiments was 50 kg dry matter cattle manure/ha/day supplemented with 2.5 kg N and 0.2 kg P/ha/day, applied twice a week. Finally, a comparison of tilapia monoculture and carp polyculture (silver carp, Hypophthalmichthys molitrix; rohu, Labeo rohita; and mrigal, Cirrhinus mrigala) was carried out to assess the best fertilization strategy determined from the tank under more commercially realistic conditions in earthen ponds (200m2). A monoculture of tilapia with no input was also included in the design to assess the pond basal fertility. The net extrapolated yield of tilapia without input was negative, compared to 3.83 t/ha/yr in fertilized tilapia ponds and 3.13 t/ha/yr in fertilized carp polyculture ponds. It is suggested that the yield of tilapia in earth ponds could be increased by increasing the rate of fertilization but that the yield of the carp polyculture could not be increased further by increasing fertilization rate as the latter system already reached to a danger level in terms of dawn dissolved oxygen. A maximum gross return of 61,033 Baht/ha/yr on the basis of Northeast Thailand price could be obtained from tilapia monoculture if manure were available on the farm as a non-cash input. The fertilization strategy developed in this study has potential for a country like Bangladesh where manure from draught cattle is underutilized and where capital intensive methods of aquaculture such as integration with feedlot livestock and the use of commercial pelleted feed are not feasible. |
| Year | 1990 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. AE-90-02 |
| 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 | Agricultural and Food Engineering (AE) |
| Chairperson(s) | Edwards, Peter; |
| Examination Committee(s) | Lin, C. Kwei;Knud-Hansen, C. F.;Chongrak Polprasert;Hopkins, Kevin D;Boyd, Claude E.; |
| Scholarship Donor(s) | Government of Australia; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 1990 |