Pond Dynamics

Note: Schedule has been revised. See Addendum to the Ninth Work Plan

Collaborating Institution
Auburn University

Claude E. Boyd
C. Wesley Wood

Objectives
1) To describe physical and chemical characteristics of the bottom soil profiles in ponds at freshwater PD/A CRSP sites (Philippines and Ayutthaya, Thailand) and at brackishwater shrimp ponds at Ranot, Thailand

2) To measure changes in concentrations of carbon, nitrogen, and phosphorus in pond soils over time at PD/A CRSP sites (AIT, Thailand; Comayagua and Choluteca, Honduras; and Sagana, Kenya) and ascertain if soil respiration and availability of nitrogen and phosphorus to water are affected by these changes.

Significance
There has been relatively little work on the role of bottom soils in pond aquaculture (Boyd, 1995). For years, aquaculturists largely ignored bottom soils, but as production levels have increased, it has become apparent that bottom soils are an important factor in pond dynamics (Boyd, 1995; Boyd and Bowman, 1997). In recognition of the importance of pond soils, the PD/A CRSP Continuation Plan contains a bottom soil component in the pond dynamics research priorities.

The proposed work is a continuation of previous PD/A CRSP efforts in pond soil research. Bowman (1992) proposed a workable system of pond soil classification based on characteristics of the surface layer. Munsiri et al. (1995) found that pond soils quickly develop profiles such as those found in terrestrial soils. They suggested that these profiles could be used to improve pond soil classification by allowing the techniques of Soil Taxonomy (Soil Survey Staff, 1994) to be applied. However, in order to initiate the use of Soil Taxonomy techniques in pond soil classification, data on bottom soil profiles are needed for a diverse group of pond soils. So far, data have been collected for freshwater pond soil profiles in Alabama and Mississippi (Munsiri et al., 1995); PD/A CRSP sites in Abbassa, Egypt (former site); AIT campus, Bangkok, Thailand; Comayagua, Honduras; and Sagana, Kenya; and at the Brackishwater PD/A CRSP site in Choluteca, Honduras (Munsiri et al., 1996; Boyd et al., 1997). The PD/A CRSP project has already committed funding to obtain samples from the freshwater site in Iquitos, Peru, during the current work plan.

Organic matter and nutrient concentrations in pond soil profiles change over time (Tucker, 1985; Munsiri et al., 1995; Boyd, 1995), and these changes influence the availability of nitrogen and phosphorus in pond ecosystems (Masuda and Boyd, 1994; Boyd, 1995). Therefore, in addition to the effort on profiles and soil classification, samples are being collected annually at four sites (AIT campus, two sites in Honduras, and Kenya) to evaluate changes in organic matter and nutrient concentrations and availability over time. This effort has been funded for the current work plan.

The proposed research would provide enough additional information from pond soil profiles in different areas to initiate work on a pond soil classification scheme. The work also will show how changes in organic matter and nutrient concentrations in pond soil influence the availability of nitrogen and phosphorus.

Anticipated Benefits
This is a continuation of studies conducted on pond soil profiles, and when this work unit is complete, data will be available for pond soil profiles to include brackishwater and freshwater ponds from 12 sites of different soil characteristics representing four continents and seven countries. This will be sufficient data on soil profiles upon which to begin to integrate pond soils into the existing system of Soil Taxonomy (Soil Survey Staff, 1994). At the completion of this work unit, there will be four years of data on changes in soil organic matter, nutrient concentrations and nutrient availability over time. The data also will be useful in providing a complete description of bottom soil characteristics at the Philippine and Ayutthaya, Thailand, PD/A CRSP sites. The soil classification system will be useful in predicting the limitations of pond soils in host countries and in pond aquaculture in general. The information on changes in nutrient availability over time and site soil characteristics will be especially useful on pond fertilization research and in the practice of pond fertilization.

Identification of Beneficiaries
The most important benefit of this study will be the development of a data base upon which to bring pond soils into the existing system of Soil Taxonomy. This will be of wide interest to researchers, extension agents, and fish and shrimp farmers. The information on changes in soil characteristics and nutrient availability over time is of general scientific interest, and small-scale farmers near PD/A CRSP sites and in neighboring countries will benefit from the findings through improvements in methods of pond fertilization. This study also will be valuable to solving soil-related problems in the US baitfish, channel catfish, and sportfish industries. One PI (C.E. Boyd) has soil projects funded by the Southern Regional Aquaculture Center in the US, and this study will complement that effort.

Collaborative Arrangements
This study will be implemented at PD/A CRSP sites through a collaborative effort of the US and host-country PD/A CRSP participants. The part of the work done on brackishwater ponds in Thailand will be done with the collaboration of the Dr. Prasert Munsiri, Director, Ranot Brackishwater Station, Thailand Department of Fisheries.

Study Design
Sites: Field research facilities at PD/A CRSP sites in the Philippines, Thailand, Honduras, and Kenya, and research ponds at the Ranot Brackishwater Station, Thailand.

Pond Facilities: Three (0.1-ha or size available) earthen ponds at each site.

Culture Period: Variable, but samples will be taken during the last month of the culture period if possible.

Stocking Rate: Variable, but we plan to use ponds stocked at fish biomass equivalent to about
1,000 kg/ha and shrimp ponds stocked at about 30 individuals/m².

Water Management: Water will be added to replace evaporation and seepage in freshwater ponds and 5% water exchange in brackishwater ponds.

Other Inputs: Nitrogen and phosphorus fertilizers will be applied to PD/A CRSP ponds at rates determined by the experiment in progress. Shrimp feed will be applied to brackishwater ponds at 3 to 5% of body weight per day. Lime inputs are acceptable.

Test Species: Nile tilapia (Oreochromis niloticus) in freshwater and black tiger prawn (Penaeus monodon) in brackishwater ponds.

Sampling Plan: Core samples will be taken by PIs from the Thailand sites in 1998 and from the Philippines site in 1999. The samples of surface soil for measuring changes in soil organic matter and nutrient concentrations over time will be taken in both years from the two Honduran sites and from the site in Kenya by resident investigators and shipped to Auburn University for analysis. The Project Leader will obtain the samples from Thailand for demonstrating changes over time during one of his visits to that country related to other business. He travels there at least twice per year. The soil cores for measuring characteristics of soil profiles will be taken with a 1-m-long, hand-operated, 5.0-cm-diameter core sampler (Wildco, Saginaw, Michigan) at water depths of 80-100 cm in each pond. Cores will extend through the soft sediment and include at least 10 cm of the original, undisturbed pond soil. Cores will be pressed upward with a plunger, cut into 2.0-cm-long segments with aid of a 2.0-cm piece of core tubing and a wide spatula (Masuda and Boyd, 1994). Segments will be processed for analysis as described by Munsiri et al. (1995). Core samples were taken from CRSP sites in Thailand and Honduras in early 1997, and analysis of data revealed that samples of the upper 4- to 5-cm layers of soil in ponds would be sufficient for detecting changes in soil chemical characteristics over time. The same ponds from which the initial cores were extracted in 1997 will be used to facilitate comparisons of data over time. The core sampler tubes will be used for obtaining the 4-cm-long core segments. Ten segments will be taken from each pond and combined to give one sample per pond. The samples will be dried at 60°C, and carried or shipped to Auburn University for analysis.

Core segments will be analyzed for bulk density, particle density, moisture content, particle-size distribution, color, pH, total phosphorus, dilute acid-extractable phosphorus, exchangeable cations (ammonia, calcium, magnesium, sodium, and potassium), and carbon. Analyses will follow standard protocol presented by Page et al. (1982) and Klute (1986). The analyses for moisture, bulk density, and color must be done on site. Other analyses will be made at Auburn University. The 4-cm-long core segments will be analyzed for particle-size distribution, pH, total phosphorus, acid-extractable phosphorus, sulfur, exchangeable cations (ammonium, calcium, magnesium, sodium, and potassium), and carbon.

Mineralization studies for carbon and nitrogen will be done on selected core segments. Mineralization studies will be conducted in vitro by placing 25 g of dry soil and 20 ml water in sealed chambers and trapping CO₂ evolved in alkali solution for measurement. Ammonia and nitrate in soil will be determined before and after incubation to determine rates of change. Aerobic incubation will be made for 30 days at 25°C, and anaerobic incubations will be made for 7 days at 25°C. Phosphorus dissolution studies will be done by placing 2-g samples of soil in 100 ml of distilled water and shaking to equilibrium phosphorus concentration on an oscillating shaker.

Statistical Methods and Hypotheses: The appropriate null hypotheses are as follows: Objective 1, soil physical and chemical characteristics do not change with soil depth; Objective 2, soil physical and chemical composition do not change over time in pond bottoms at any of the sites, and samples from all sites and for all years have the same rates of carbon and nitrogen mineralization and phosphorus solubility.

The data on soil profiles will be plotted as concentration of each soil variable versus depth. Depths will be grouped into layers to obtain increased homogeneity of variances (Kingery et al., 1994). Data will be analyzed as a split plot within each soil layer. Site will be the main plot, and soil depth within a layer will be the split plot. Ponds will be replications. Data from laboratory mineralization and microcosm studies will be compared statistically by t-tests.

Regional Integration
This project integrates well into the regional plan. The information obtained will be useful for identification of pond soils and for use in modifying pond fertilization methods for local conditions in the countries surrounding the PD/A CRSP sites.

Statement on Contribution to Region
This study will be 70% in Asia, 15% in Central America, and 15% in Africa.

Schedule
The core samples in Thailand will be collected in November or December 1998 and those in the Philippines will be taken in November or December 1999. Annual samples from Thailand, Honduras, and Kenya will be taken during July 1998, July 1999, and in April 2000.

Final Report
The final report will be submitted by 30 June 2000.

References
Bowman, J.R. 1992. Classification and management of earthen aquaculture ponds, with emphasis on the role of the soil. Ph.D. Dissertation, Corvallis, OR: Oregon State University.
Boyd, C.E., 1995. Bottom Soils, Sediment, and Pond Aquaculture. Chapman and Hall, New York.
Boyd, C.E. and J.R. Bowman, 1997. Pond bottom soils. In: H.S. Egna and C.E. Boyd (Editors), Dynamics of Pond Aquaculture. CRC Press, Boca Raton, pp. 135-162.
Boyd, C.E. and C.W. Wood, 1997. Pond Soil Characteristics and Dynamics of Soil Organic Matter and Nutrients. Unpublished Annual Report for Work Plan 8 submitted to PD/A CRSP, Oregon State University, Corvallis, OR.
Kingery, W.L, C.W. Wood, D.P. Delaney, J.C. Williams, and G.L. Mullins, 1994. Impact of long-term land application of broiler litter on environmentally related soil properties. J. Environ. Qual., 23:139-147.
Klute, A., 1986. Methods of Soil Analysis, Part I. American Society Agronomy, Madison, WI.
Masuda, K. and C.E. Boyd, 1994. Phosphorus fractions in soil and water of aquaculture ponds built on clayey, Ultisols at Auburn, Alabama. J. World Aquacult. Soc., 25:379-395.
Munsiri, P., C.E. Boyd, and B.J. Hajek, 1995. Physical and chemical characteristics of bottom soil profiles in ponds at Auburn, Alabama, and a proposed method for describing pond soil horizons. J. World Aquacult. Soc., 26:346-377
Munsiri, P., C.E. Boyd, B.W. Green, and B.F. Hajek, 1996. Chemical and physical characteristics of bottom soil profiles in ponds on haplaquents in an arid climate at Abbassa, Egypt. J. Aquacult. Tropics, 11:319-329.
Page, A.L., R.H. Miller, and D.R. Keeney, 1982. Methods of Soil Analysis, Part II. American Society of Agronomy, Madison, WI.
Soil Survey Staff, 1994. Keys to Soil Taxonomy, 4th edition. Soil Management Support Monograph No., 19, Virginia Polytechnical Institute and State University, Blacksburg, VA.
Tucker, C. S., 1985. Organic matter, nitrogen, and phosphorus content of sediments from channel catfish Ictalurus punctatus ponds. Miss. Agr. Forestry Exp. Sta., Miss. State Univ., Res. Rep. 10.