David Teichert-Coddington and Claude Boyd, International Center for Aquaculture and Aquatic Environments, Department of Fisheries and Allied Aquacultures, Auburn University, Alabama 36849 USA
Delia Martinez de Pinel, Laboratorio de Calidad de Agua, Centro de Capacitación La Lujosa, Ministerio de Recursos Naturales, Choluteca, Honduras
14 August 1997, CRSP Research Report 97-111
Abstract Diammonium phosphate, monoammonium phosphate, triple superphosphate, and urea were dropped through a 1-m column of water which ranged from 0 to 40 ppt salinity. Mean solubility of nitrogen was 4.1% from diammonium phosphate, 11.8% from monoammonium phosphate, and 76.8% from urea. Mean solubility of phosphorus was 4.6% from diammonium phosphate, 10.4% from monoammonium phosphate and 4.4% from triple superphosphate. Salinity did not significantly affect the solubility of nitrogen and phosphorus from diammonium phosphate. Nitrogen solubility from monoammonium phosphate and phosphorus solubility from triple superphosphate significantly decreased with increasing salinity, but the correlations were low. Urea solubility and phosphorus solubility from monoammonium phosphate responded curvalinearly to increasing salinity. Solubility differences caused by salinity disappeared after 24 h of contact with water when all fertilizers dissolved completely regardless of salinity. No adjustment for salinity is necessary when fertilizer rates are calculated for brackish water or marine application.
This abstract was excerpted from the original paper, which was published in Journal of the World Aquaculture Society, 28(2):205-210.
Claude Boyd and Prasert Munsiri, Department of Fisheries and Allied Aquacultures, Auburn University, Alabama 36849 USA
14 August 1997, CRSP Research Report 97-112
Abstract Forty-five soil samples were collected from aquaculture areas in 23 provinces of Thailand to include six soil orders and wide variation in physical and chemical properties. Soil-water microcosms were prepared containing 5 g of soil and 150 mL of distilled water. Microcosms were held in an oscillating table shaker (150 rpm) for 1 wk at 25 C in the dark. Water pH and concentrations of dissolved nutrients, total alkalinity, and total hardness were measured. Differences in properties within soil orders caused wide variation in composition of solutions and differences in concentrations of dissolved substances and pH were not related to order. Regression analyses revealed significant correlations between concentrations of soil nutrients extractable in dilute acid (0.05 N HCl plus 0.025 N H2SO4) or in neutral, 1 N ammonium acetate and aqueous concentrations. Regression coefficients usually were higher for dilute-acid extractable nutrients than for ammonium acetate extractable ones. Regression coefficients based on dilute-acid nutrients follow: soluble reactive phosphorus (r = 0.816); calcium (r = 0.685); magnesium (r = 0.470); potassium (r =0.959); sodium (r = 0.977); manganese (r = 0.462); boron (r = 0.399). The correlation between soil and solution iron was not significant and aqueous concentrations of copper and zinc were below detection limit. Hardness was correlated with soil carbon (r = 0.710) and soil pH was a good predictor of alkalinity (r = 0.877). Soil pH and aqueous pH were highly correlated (r = 0.939). Findings suggest that soil characteristics can be used to predict pH and concentrations of several dissolved substances in soil-water systems under aerobic conditions.
This abstract was excerpted from the original paper, which was published in Journal of the World Aquaculture Society, 28(2):165-170.
Madhav K. Shrestha and C. Kwei Lin*, Asian Institute of Technology, Agriculture and Aquatic Systems, Program P.O. Box 4 Klong Luang, Pathumthani 12120, Thailand
14 August 1997, CRSP Research Report 97-113
Abstract An experiment was conducted to determine the amount of P needed to saturate simulated fish ponds sediments, formulated to contain six levels of clay (0, 30, 41, 64, 73 and 81% by weight). A series of cylindrical cement tanks were filled to 20 cm depth with the six sediment types and triple superphosphate (TSP) solution was added to reach P saturation in sediment. Results showed that all sediment types reached a constant inorganic-P concentration in the upper 5 cm after 12 weeks of TSP application, and P adsorption capacity of sediment increased with increasing clay content. Sediment P adsorption was slower and not significant (P>0.05) below 5 cm depth except in the sediment type containing 0% clay. Regression analysis showed that the rate and adsorption capacity of P in sediment are primarily governed by clay content and its dominant minerals. While organic-P and loosely bound-P are commonly deposited in sediment, most inorganic-P is adsorbed by cations to form cation-P complexes. The linear relationship between cation-P saturation level and the percentage of clay in sediment is highly significant (r2 - 0.84, P<0.001) and, therefore, the maximum adsorption capacity of cation-P in pond sediment can be approximated by Y = 0.019X (where Y represents the 100% saturation level in mg P g-1 soil, and X is the percentage of clay in the sediment). In practice, the level of P saturation in sediment can be approximated by the intial cation-P and clay contents in the top 5 cm of pond mud using the equation: P saturation (%) = initial cation-P (mg g-1 soil) x 100/P adsorption capacity (mg g-1 soil).
This abstract was excerpted from the original paper, which was published in Aquacultural Engineering, 15(6):441-459.
Madhav K. Shrestha and C. Kwei Lin*, Asian Institute of Technology, Agriculture and Aquatic Systems Program, P.O. Box 4 Klong Luang Pathumthani 12120 Thailand
14 August 1997, CRSP Research Report 97-114 (repeat of 97-101)
Abstract Two experiments were conducted to determine effective P fertilization strategy in fish ponds in relation to sediment P saturation level. Experiment 1 was conducted in cement tanks with five levels of P saturation in the sediments (5, 24, 44, 60 and 79%) and with three P fertilization rates (0.2, 0.1 and 0.05 g m-3 day-1, N:P ratios of 2:1, 4:1 and 8:1, respectively). Nile tilapia (Oreochromis niloticus) were cultured in tanks for 57 days. Results showed that the mean concentration of soluble reactive phosphorus (SRP) in the water column increased with increasing sediment P saturation and P fertilization rate. The maximum net fish yield (NFY), 4.2 ± 0.3 g m-3 day-1, was obtained at an SRP concentration of 0.3 mg l-1; higher concentrations did not increase fish yield. These levels of SRP and NFY were attainable with P fertilization rates of 0.2 g m-3 day-1, 0.1 g m-3 day-1 and 0.05 g m-3 day-1 and N:P ratios of 2:1, 4:1 and 8:1 in ponds where level of sediment P saturation was below 10%, above 45% and above 60%, respectively. Experiment 2 was conducted in earthen ponds to test and verify the P fertilization rate based on the cement tank results. Three new and three old ponds with 8 ± 1.7% and 88 ± 7.3% sediment P saturated in the top 5 cm of mud were fertilized at a rate of 0.2 g m-3 day-1 and 0.05 g m-3 day-1 and N:P ratio of 2:1 and 8:1, respectively. Nile tilapia were cultured at a density of two fish m-3 for 85 days. The mean NFY obtained in new and old ponds were 1.73 ± 0.08 g m-3 day-1 and 2.24 ± 0.32 g m-3 day-1, respectively, which were not significanty different (P>0.05). We conclude that P fertilization rate should be based on P saturation level in mud to overcome the problem of under or over supply of P in fish ponds.
This abstract was excerpted from the original paper, which was published in Aquaculture, 142(1996):207-219.
Influence of Nile tilapia (Oreochromis niloticus) stocking density in cages on their growth and yield in cages and in ponds containing the cages
Yang Yi and C. Kwei Lin*, School of Environment, Resources and Development, Asian institute of Technology, G.P.O. Box 2654, Bangkok 10501, Thailand
James S. Diana, School of Natural Resources and Environment, University of Michigan, Ann Arbor, MI 48109, USA
14 August 1997, CRSP Research Report 97-115
Abstract An experiment was conducted for 90 days at the Asian Institute of Technology in Thailand to investigate the appropriate stocking density of large Nile tilapia placed in cages in earthen ponds where small Nile tilapia were stocked in open water to utilize the wastes derived from the cages. Large male tilapia (141 ± 11.1-152 ± 2.1 g) were stocked at 30, 40, 50, 60, and 70 fish m-3 in 4-m3 net cages. One cage was suspended in each of 15 earthen ponds, and three replicates were used for each density. Small male tilapia (54 ± 2.3-57 ± 1.2 g) were stocked at 2 fish m-3 in open water of all ponds. Caged tilapia were fed twice daily at 3%, 2.5%, and 2% body weight day-1 during the first, second, and third month, respectively, with commercial floating pellets containing 30% crude protein. Water quality was analyzed biweekly.
Stocking densities of caged tilapia had significant (P<0.05) effects on the survival, growth, and food conversion ratio of caged tilapia, and on the growth of open-pond tilapia. The survival of caged tilapia decreased from 91.4% ± 5.0 to 57.2% ± 8.1 with increased stocking densities from 30 to 70 fish m-3, while survival of pond tilapia was higher than 90.0% in all treatments. The average treatment mean weights of tilapia harvested from cages ranged from 509 ± 26.0 to 565 ± 13.9 g. The growth of pond tilapia was quite slow, with daily weight gain increasing from 0.30 ± 0.02 to 0.47 ± 0.08 g per fish day-1, in response to increased feed inputs to caged tilapia. The combined net yield of both caged and open-pond tilapia was highest in the treatment with 50 fish m-3. Water quality analyses indicated that the wastes from caged tilapia were insufficient to generate abundant natural food for the growth of open-pond tilapia.
This abstract was excerpted from the original paper, which was published in Aquaculture, 146(1996):205-215.
|Previous group of reports: 97-106 to 97-110||Next group of reports: 97-116 to 97-120|