Assessment of Tilapia pond sediment properties and its efficacy to improve soil fertility | |
| Author | Rahman, Md. Mizanur |
| Call Number | AIT Diss. no.AQ-06-04 |
| Subject(s) | Tilapia Soil fertility Fish ponds |
| Note | A dissertation submitted in 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. AQ-06-04 |
| Abstract | Six experiments were conducted at the Asian Institute of Technology (AIT), Thailand during March 2003 to December 2004 to assess the physical and chemical properties of tilapia pond sediment and its efficacy to improve soil fertility. A succulent vegetable crop, morning glory (Ipomoea reptcnrs) was used as a sample crop throughout this study. The physical and chemical properties of sediment were quantified during the first experiment using a factorial design consisted in three types of pond inputs (viz. inorganic fertilizers, inorganic fertilizers plus chicken manure, and inorganic fertilizers plus feed) and two culture period (viz. 180 days and 400 days). Nile tilapia (Oreochromis niloticus) was stocked in 180-188 m2 earthen ponds at a rate of 2 fish m-2. Each treatment had three replicates. In inorganic fertilizers and inorganic fertilizers plus chicken manure treated ponds, input of 4 kg N and 1 kg P ha-1 d-1 was maintained by combining inorganic fertilizer alone or with chicken manure, and the latter was provided at a rate of 20 kg ha-1 d-1 (dry weight), on a weekly basis. In addition to inorganic N and P, pellet-ed feed (30 % protein) was applied to inorganic fertilizers plus feed ponds daily at rates of 5 %, 3 % and 1 % body weight of fish for 1-2. 3-4 and 5-13 months, respectively. Sediments from each pond were collected monthly for nutrient analysis, and the rates of sedimentation and organic matter accumulation were determined at the end of each culture period. Type of pond inputs, culture periods and their interaction had significant effects on the rates of sedimentation and organic matter (OM) accumulation. Sedimentation rates were 859, 1344 and 2173 g m-2 day-1 in inorganic fertilizers, inorganic fertilizers plus chicken manure and inorganic fertilizers plus feed ponds, respectively. The corresponding OM accumulation rates were 17, 30 and 54 g m-2 day-1, respectively. OM, N and K contents were significantly higher in sediments of ponds treated with inorganic fertilizers plus feed ponds. Treatments did not affect P, B, Cu, Fe, Mn and Zn contents of ponds sediments. Accumulation of almost all mineral nutrients was reached a plateau after 4-6 months of tilapia culture period. Pond sediment's fertility in terms of B, Cu, Fe, Mn and Zn was very high. The weight of sediment of top 10 cm layer was ranged from 63 to 72 kg m-2. The bulk density of the pond sediments treated with inorganic fertilizers was significantly higher than the rest of treatments. Mean total N and P contents in sediments were ranged from 1.97 to 2.18 g kg-1 and 182.0 to 192.5 mg kg-1, respectively, which indicated that the fertility of tilapia pond sediment can be ranked as medium and very high, respectively. This observation revealed that the fertilizer values of sediment of I ha of pond area was equivalent to 3.0 t urea and 0.7 t triple super phosphate. Physical and chemical properties of sediment over time were studied during the second experiment using five potting media comprised of different ratios of sediment and topsoil (viz. 0:100, 25:75, 50:50, 75:25 and 100:0 sediment: topsoil). Soft sediment was collected from the top 10 cm of the pond bottom of tilapia ponds fertilized with inorganic fertilizers and feed for a period of 180 days. Sediment and topsoil were air-dried and mixed as per treatments. Each pot contained 8 kg of potting media. The pots were kept in the lath house for two time periods, viz. 1 month and 2 months, and allowed for rebuilding soil structure without growing crops in pots. After the assigned time periods soils samples from each pot were collected and determined the amount of water stable soil aggregates, moisture content and soil pH. Soil pH, water stable soil aggregates and moisture retention linearly increased with inclusion levels of sediment component in the potting media. The third experiment was conducted to evaluate the fertilizer requirements of morning glory using four levels of N (0.1, 0.2, 0.3 and 0.4 g N pot-1), two levels of P (0.05 and 0.10 g P pot-1) and two levels of K (0.07 and 0.14 g K pot-1) in a factorial design. Crop was harvested at 45 days after seeding. The plant tissues were analyzed and N, P and K requirements for morning glory were found to be 0.55, 0.10 and 0.48 g pot-1, respectively. Estimated N. P and K requirements of morning glory taking the surface area of a pot into account (0.0177 m2) were 310, 56 and 269 kg ha-1, respectively. The supplementary fertilization value of pond sediments for morning glory was assessed in the fourth experiment using a 3x3 factorial design i.e. three levels of N (0.35, 0.55 and 0.98 g N pot-1) and P (0, 0.05 and 0.10 g P pot-1) taking 100% air dried sediment in pots. Potassium was applied at a rate of 0.48 g pot-1 to all treatments. Corresponding amounts of N, P and K were applied to pots using urea, triple super phosphate and muriate of potash, respectively. Crop was harvested at 45 days after seeding and found that N application up to 0.55 g pot-1 significantly increased total dry matter production, and P and K uptake of morning glory. The effects of P application on total dry matter production, and N, P and K uptake were not significant, which indicated that 100% P requirement of morning glory was satisfied by pond sediments. It was estimated that sediment can satisfy 37% N and 24% K requirements of morning glory. Residual P content of pots supplied with only pond sediments was 60 mg P kg-1 after crop harvest, which indicated that pond sediment can benefit even the follow up crop grown in soils treated with pond sediment. In addition, sediments can be diluted at a rate of 1: 3 (sediments: topsoil) to satisfy P requirements of morning glory. The agricultural benefits of tilapia pond sediment were assessed during the fifth experiment using five treatments containing different ratios of sediment and topsoil i.e. 0: 100, 25:75, 50:50, 75:25 and 100:0 sediment: topsoil. N, P and K were provided from inorganic fertilizers in the control treatment (0: 100). P was supplied solely from sediment in other treatments, but N and K were supplemented using inorganic fertilizer. Crop was harvested at 45 days after seeding and plant samples were analyzed for nutrient contents. Soil aggregate stability and pH were determined in soils after crop harvest. Total dry matter production and N and P uptake of morning glory were not significantly different between the control treatment and 25% sediment treatment. Increasing the rate of sediment in topsoil from 25 to 75% did not significantly improve the fresh yields of morning glory. This showed that application of 25% sediment can meet the P requirement for morning glory, while improving both soil aggregate stability and pH. Economic returns of morning glory culture on the dike using sediment were estimated during the 6"' experiment. Sediment was collected from the top 15 cm of the pond bottom of tilapia ponds fertilized with inorganic fertilizers and feed for a period of 400-days. Morning glory was grown in triplicate in 1 x 1 m2 plots using eight treatments: (1) zero input control (SoNoPoKo), (2) fertilizer control - plot soil plus inorganic N, P and K (SoNPK), (3) plot soil plus 60 kg sediment (S60N0P0K0), (4) plot soil plus 60 kg sediment and inorganic K (S60N0P0K0), (5) plot soil plus 60 kg sediment and inorganic N and K (S60NPOK), (6) plot soil plus 120 kg sediment (S120N0P0K0), (7) plot soil plus 120 kg sediment and inorganic K (S120N0P0K) and (8) plot soil plus 120 kg sediment and inorganic N and K (S120NPOK). Sixty and 120 kg pond sediment corresponds to 30 and 60% of the plot's soil. Therefore, 60 and 120 kg of plot soil was removed and replaced with an equal amount of pond sediment and thoroughly mixed. The results showed that mixing 30% sediment into topsoil and supplementing N and K at rates of 16.9 and 32.4 g m2, respectively, can provide sufficient nutrients for morning glory. The fresh yields of morning glory grown on S60NPOK treatment were not significantly different from the fertilizer control treatment (S0NPK), however, the gross margin was significantly higher in the fertilizer control treatment due to its lower labor requirement. The experimental results on sedimentation and nutrient enrichment of sediment in tilapia fishponds suggest that sediment can be harvested after 4-6 months of tilapia culture. With the Supplementation of N and K, inclusion of 25-30% sediment (by weight) to farm soils can satisfy all nutrient requirements of morning glory. In addition, inclusion of sediment at a rate of 50% sediment was shown to improve soil aggregate stability, and increase in pH and water holding capacity of farm soils better than lower inclusion rates. It is expected that these research findings would encourage the farmers to use sediment for agricultural soils and to integrate aquaculture-agriculture enterprises, thus making farming systems more sustainable. |
| Year | 2006 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. AQ-06-04 |
| 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.;Yi, Yang;Verdegem, Marc C.J.; |
| Scholarship Donor(s) | Asian Institute of Technology Fellowship; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2006 |