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PD/A CRSP Aquanews-Summer 2001
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Notice of Publication

This Notice of Publication announces recently published work carried out under PD/A CRSP sponsorship. To receive a full copy of a report, please contact the author(s) directly unless it is otherwise noted.

Research Report 01-169

Pond soil pH measurement

Taworn Thunjai and Claude E. Boyd
Department of Fisheries and Allied Aquacultures
Auburn University, Alabama 36849 USA

Karen Dube
Central Institute of Fisheries Education
Verosa, Mumbai 400061 India

Soil pH often is measured in samples from the bottoms of aquaculture ponds. Several different techniques for soil pH are used. This study considered the differences in pH obtained by the different methods and determined which methods appeared most useful. Dual electrodes (indicating and reference) and a single-probe combination electrode gave similar pH values when inserted into 1:1 mixtures of dry soil and distilled water. There were slight differences in pH between readings with dual and combination electrodes when the dual electrodes were arranged with the indicating electrode in the sediment phase and the reference electrode in the supernatant phase of the mixture. The two-phase method with the dual electrode does not appear warranted because of greater difficulty in making measurements. Dry soil : distilled water ratios of 1:2.5, 1:5, and 1:10 had progressively greater pH readings than obtained at a 1:1 ratio. Measurements made in 0.01 M CaCl2 and 1.0 M KCl had much different values than those made in distilled water. Higher pH resulted when pH was measured without stirring or in filtrates of soil-water mixtures. A 20-min period of intermittent stirring before making measurements was necessary for a stable pH value. Particle size did not influence pH in aliquots passing 0.053 to 2.36-mm sieves. Drying temperature had a strong influence on pH, and measurements made on samples dried at 40 to 60 C are probably most reliable. Measurements of in situ pH in wet soil with standard pH electrode or a portable acidity tester differed greatly from those made in 1:1 dry soil to distilled water mixtures. Pond bottom soil pH measurement should be standardized. Based on findings of this study, the following method is suggested: dry soil at 60 C in a forced-draft oven; pulverize soil to pass a 2-mm sieve; mix soil and distilled water in a 1:1 ratio (weight : volume); stir intermittently with glass rod for 30 min; insert dual electrodes or a combination electrode into the mixture; measure pH while stirring.

This abstract was based on the original paper, which was published in Journal of the World Aquaculture Society, 32(2):141–152.

Research Report 01-170

Nonparametric estimation of returns to investment in Honduras shrimp research

Siddhartha Dasgupta and Carole R. Engle
Aquaculture/Fisheries Center
University of Arkansas at Pine Bluff
1200 N. University, Mail Slot 4912
Pine Bluff, AR 71601 USA

Economic returns to the investment in shrimp research in Honduras by Auburn University researchers, as a part of the Pond Dynamics/Aquaculture Collaborative Research Support Program (1993 to 1998), were estimated using a nonparametric approach. A survey of shrimp growers in Honduras provided data on yield, input application, and prices for their first year of production and for the year 1997. Research investment data included funding from both public and private sectors. Results showed that total factor productivity indices increased from 1995 to 1997 indicating technical progress due to research. When both private and public investment were considered, the internal rate of return to the investment in research was 46%. However, the internal rate of return to public-sector investment alone was above 6,681%. This indicated that the public funds invested in shrimp research in Honduras have been leveraged effectively with private-sector capital to generate technological progress.

This abstract was based on the original paper, which was published in Aquaculture Economics and Management, 4(3–4):141–156.

Research Report 01-171

Risk analysis of shrimp farming in Honduras

Diego Valderrama and Carole R. Engle
Aquaculture/Fisheries Center
University of Arkansas at Pine Bluff
1200 N. University, Mail Slot 4912
Pine Bluff, AR 71601 USA

Honduras is the leading producer of pond-raised shrimp in Central America, but profitability of operations is affected by fluctuating yields and prices which generate economic risk. An analysis of the financial risks associated with different management strategies would provide useful management guidelines. Data from a 1997 survey were used to develop enterprise budgets and a risk analysis for three farm-size scenarios (73, 293, and 966 ha) and for a group of farms exhibiting an alternative, more intensive level of semi-intensive technology (AST farms). Economies of size related to fixed costs and to feed, repair, and interest costs were identified. Net returns/ha were highest for the AST farms while low net returns/ha reported by the other farm groups were connected with low yields, conservative input usage rates, poor survivals, and economies of size. To minimize potential for loss, farms should target a minimum acceptable yield that would vary with farm size.

This abstract was based on the original paper, which was published in Aquaculture Economics and Management, 5(1–2):49–68.


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