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Effects of Pond Age on Bottom Soil Quality 10PDR1

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Effects of Pond Age on Bottom Soil Quality

Pond Dynamics Research 1 (10PDR1)/Study/Thailand

Collaborating Institutions
Kasetsart University, Thailand
      Mali Boonyaratpalin

Auburn University
     Claude E. Boyd

Objectives
This proposal focuses on the PD/A CRSP production optimization objective to increase the overall sustainability of aquacultural production systems through production optimization and the pond dynamics research theme objective to further our understanding of the influence of pond processes on pond productivity. The study will consider pond soil quality and the specific objectives are:

1) Determine relationships between pond age and several key bottom soil quality variables (pH, exchangeable acidity, thickness of S-horizon, bulk density, total sediment depth, lime requirement, organic carbon, and reactivity of organic matter).

2) Evaluate the neutralizing value, particle-size distribution, and calcium and magnesium content of liming materials normally used by fish farmers in Thailand, and use data on soil characteristics and liming materials to improve the lime requirement technique.

3) Compare different methods of pond soil organic matter analyses.

4) Prepare recommendations on pond bottom soil management that consider changes in soil quality as ponds.

Significance
It has been suggested that organic matter increases in bottom soils as ponds age until an equilibrium organic matter concentration is attained (Avnimelech, 1984; Boyd, 1995). Studies have shown that new ponds have lower concentrations of soil organic matter than older ponds, but information on the rate of increase in organic matter over time is lacking (Munsiri et al., 1995, 1996). Organic matter consists of fresh material that decomposes rapidly and older, more stable material that decomposes more slowly (Munsiri et al., 1995). Soil respiration rate measured as carbon dioxide evolution increases with increasing organic matter concentration (Sonnenholzner and Boyd, 2000). However, no studies have considered if the rate of carbon dioxide evolution per unit of organic matter decreases as ponds become older and more stable organic matter accumulates in pond soils. This information is needed to properly assess organic matter concentrations in pond bottom soils.

Many studies of bottom soil organic matter, including studies supported by PD/A CRSP, used an induction furnace carbon analyzer for making the analyses. Few laboratories that do analyses for aquaculture purposes have carbon analyzers, and less expensive procedures for estimating soil organic carbon such as sulfuric acid-potassium dichromate oxidation (Walkley-Black method) or dry ashing are often used (Nelson and Sommers, 1982; Baldock and Nelson, 2000). An evaluation of the different carbon analysis methods is needed so that correlations can be developed to facilitate comparisons of pond soil organic matter data obtained by different methods.

Methods for lime requirement of pond soil samples are available (Boyd, 1995), but these methods have not been adjusted for the depth and bulk density of the S-horizon. Most existing methods for calculating lime requirements of pond soils use values for the average bulk density of agricultural soils to a depth of 15 cm. These procedures will over estimate lime requirement because the bulk density of the S-horizon is much less than that of normal agricultural soil and the S-horizon usually is less than 15 cm deep (Munsiri et al., 1995). Lime requirements also are based on finely-pulverized calcium carbonate with a neutralizing value of 100% (Adams and Evans, 1962; McLean, 1982). Liming materials used by fish farmers may differ greatly from the calcium carbonate standard used for calculating lime requirement.

The acquisition of more precise information on changes in pond bottom soils and data on variation in liming material characteristics are critical for refining pond soil management protocol. These data will reveal if lime requirement computations should be adjusted for pond age and source or type of liming material. Knowledge of the rate of soil organic matter accumulation and any changes in the reactivity of organic matter as ponds age will be valuable in determining how often ponds should be drained and their bottoms dried in order to enhance organic matter decomposition. Findings of the study will be used to develop a pond soil management protocol that considers pond age as a factor.

The study described in this proposal fits well under the Pond Dynamics research theme of the RFP and Continuation Plan. The Pond Dynamics theme specifically mentions the need to characterize pond sediment to obtain information needed in the development of more effective pond management techniques.

Quantified Anticipated Benefits
The overall benefit expected from this project will be the development of some specific soil management practices for use by farmers in Thailand and other countries to improve soil quality in fish ponds.

Specific benefits are expected as follows:
1) More efficient calculations of liming rates and use of liming materials. This should result in an economic savings on liming material and better pond soil pH.

2) More efficient pond dry-out schedule for reducing organic matter accumulation. This will minimize pond "down-time" between crops for some farmers and improve bottom soil condition for other farmers.

3) The data on changes in soil quality with pond age will be useful in educating farmers on pond dynamics. This information will benefit extension personnel and farmers.

Research Design
Pond Facilities: Ponds for use in this work will be located on private fish farms and at fisheries research stations in central Thailand. These ponds will be 2,000 to 5,000 m2 in area with average depths of about 1 to 1.5 m. Ponds that have only been used for tilapia culture will be sought, and an attempt will be made to select ponds that are similar with respect to stocking densities, fertilization and feeding regimes, and other management inputs. Only ponds that have been in continuous production for a known number of years will be selected. We plan to select at least 25 ponds for use in the study, and if possible, 35 to 40 ponds will be used.

Research Plan and Methodology: Ponds of different (but known) ages will be located by the Thailand Department of Fisheries and will be farmer ponds or ponds on research stations. Information on pond management history for each pond will be obtained from owners or managers. Core samples will be collected from five places near the bottom of each pond with a 5-cm diameter core tube. The cores will be inspected and the depths of the S-horizon and the total sediment depth will be measured. Munsiri et al. (1995) describes how to identify the thickness of the S-horizon and total sediment depth by visual inspection. The core segment representing the S-horizon will be pushed out of the core tube, cut, and saved in a plastic container. All cores from a pond will be combined to provide a single, composite sample. These samples will be oven dried at 60°C. A separate set of cores from the S-horizon will be placed in soil moisture cans of known weight and dried at 105°C for determination of dry bulk density (Blake and Hartge, 1986). Dry samples will be transported to Auburn University for analytical work. The samples dried at 60°C will be pulverized with a mechanical soil crusher to pass a 40-mesh screen and saved for chemical analyses and determination of the reactivity of the organic matter.

Soil pH will be determined by glass electrode in 1:1 mixtures (weight/volume) of dry soil and distilled water (Thunjai et al., 2001). Exchangeable acidity will be measured by the procedure of Pillai and Boyd (1985) and the lime requirements estimated based on bulk density, depth of S-horizon, and exchangeable acidity.

Soil organic matter will be determined by three techniques: Leco carbon analyzer, dry ashing at 350°C for 8 hr (Jackson, 1958), and the Walkley-Black sulfuric acid-potassium dichromate oxidation (Nelson and Sommers, 1982).

Reactivity of organic matter will be determined in aerobic, laboratory incubation chambers by a carbon dioxide evolution technique described by Sonnenholzner and Boyd (2000). Portions of acidic samples will be treated with agricultural limestone to neutralize exchangeable acidity and reactivity will be determined on both limed and unlimed portions.

Samples of liming material will be analyzed for particle size distribution and neutralizing value by methods presented by Boyd (1995). Samples will be dissolved in acid, and calcium and magnesium determined by EDTA titration using eriochrome black-T and murexide, respectively, as indicators.

Statistical Analysis: The nature of this study does not allow for replication of pond ages as treatments. The data will be analyzed primarily by regression analysis using age as the dependent variable and soil quality variables as independent variables.

Regional Integration
The project will integrate well into the regional plan. The changes that occur in fish pond soils over time are not expected to be country specific or even region specific. These changes should occur in all ponds in similar climatic areas that are managed in a similar way. Thus, the pond management information should be useful within the region and even outside of the region.

Schedule
The tentative schedule follows:
July 2001 Begin project. Trip to Thailand to collect samples of soil and liming materials.
July 2001-May 2002 Analyze samples and resulting data.
June 2002 Trip to Thailand to collect additional samples.
June-December 2002 Finish analyses. Develop better practices based on data.
January 2003 Trip to Thailand to collect samples needed to fill in gaps in data and to refine practices.
February-April 2003 Prepare final report.

Literature Cited
Adams, F. and C.E. Evans, 1962. A rapid method for measuring lime requirement of red-yellow podzolic soils. Soil Science Society of America Proceedings, 26:355­357.

Avnimelech, Y., 1984. Reactions in fish pond sediments as inferred from sediment cores data. Publication No. 341, Technion Israel Institute of Technology, Soils and Fertilizers Research Center, Haifa, Israel.

Baldock, J.A. and P.N. Nelson, 2000. Soil organic matter. In: M.E. Summer (Editor), Handbook of Soil Sciences, CRC Press, Boca Raton, Florida, pp. 1325­1384.

Banerjea, S.M., 1967. Water quality and soil condition of fish ponds in some states of India in relation to fish production. Indian Journal of Fisheries, 14:113­114.

Blake, G.R. and K.H. Hartge, 1986. Bulk density. In: A. Klute (editor), Methods of Soil Analyses, Part 2, Chemical and Microbiological Properties. American Society of Agronomy, Madison, Wisconsin, pp. 363­375.

Boyd, C.E., 1995. Bottom Soils, Sediment, and Pond Aquaculture. Chapman and Hall, New York, 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, Florida, pp. 135­162.

Boyd, C.E., M. Tanner, M. Madkour, and K. Masuda, 1994. Chemical characteristics of bottom soils from freshwater and brackishwater aquaculture ponds. Journal of the World Aquaculture Society, 25:517­534.

Jackson, M.L., 1958. Soil Chemical Analysis. Prentice-Hall, Englewood Cliffs, New Jersey.

McLean, E.O., 1982. Soil pH and lime requirements In: A.L. Page, R.H. Miller, and D.R. Keeney (Editors), Methods of Soil Analysis, Part 2, Chemical and Microbiological Properties of Soil. American Society of Agronomy and Soil Science Society of America, Madison, Wisconsin, pp. 199­224.

Munsiri, P., C.E. Boyd, and B.F. Hajek, 1995. Physical and chemical characteristics of bottom soil profiles in ponds at Auburn, Alabama, and a proposed method for describing pond soil horizons. Journal of the World Aquaculture Society, 26:346­377.

Munsiri, P., C.E. Boyd, D. Teichert-Coddington, and B.F. Hajek, 1996. Texture and chemical composition of soils from shrimp ponds near Choluteca, Honduras. Aquaculture International, 4:157­168.

Nelson, D.W. and L.E. Sommers, 1982. Total carbon, organic carbon, and organic matter In: A.L. Page, R.H. Miller, and D.R. Keeney (Editors), Methods of Soil Analysis, Part 2, Chemical and Microbiological Properties. American Society of Agronomy, Madison, Wisconsin, pp. 539­579.

Pillai, V.K. and C.E. Boyd, 1985. A simple method for calculating liming rates for fish ponds. Aquaculture, 46:157­162.

Sonnenholzner, S. and C.E. Boyd, 2000. Vertical gradients of organic matter concentration and respiration rate in pond bottom soils. Journal of the World Aquaculture Society, 31:376­380.

Thunjai, T., C.E. Boyd, and K. Dube, 2001. Pond soil pH measurement. Journal of the World Aquaculture Society, 32. (in press)

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