Objectives
1) To describe physical and chemical characteristics of the soil profile in ponds at the PD/A CRSP site in Peru.

2) To determine changes over time in concentrations of soil physical and chemical properties in surface soil layers in ponds at all PD/A CRSP sites.

3) Estimate rates of carbon and nitrogen mineralization and phosphorus dissolution in pond soils at all PD/A CRSP sites.

Significance
This unit of work will provide a description of physical and chemical characteristics of pond soil cores from the CRSP site in Peru. This will be the tenth site for which such core analyses are available. Other sites are Abbassa, Egypt; Auburn, Alabama (two sites); Comyagua and Choluteca, Honduras; Bangkok, Thailand; Kenya; Greenville, Mississippi; and Greensboro, Alabama. It is anticipated that we will have enough diverse sites represented in our data base to begin developing a system of pond soil taxonomy. The data also will provide a second year of analyses for the sites in Thailand, Honduras, and Kenya to use in evaluation of changes in pond soils over time. Of course, we plan to continue the annual sampling in the same three ponds at each site in Thailand, Honduras, Kenya, and Peru.

Anticipated Benefits
The information will be beneficial to the overall CRSP project in that it will provide a careful description of the soil from research ponds at each Core Site. The data will be important to aquaculture in general because it will provide information on organic matter decomposition and accumulation in pond bottom soils and estimates of nitrogen and phosphorus availability from pond soils to the water column. Organic matter dynamics and nutrient availability are critical issues in pond management because organic matter decomposition affects dissolved oxygen availability and redox potential at the soil-water interface, and the availability of nutrients from the soil to the water column influences the amount of fertilizer that must be applied to enhance primary productivity. We expect that the results of this study will be useful in improving pond bottom soil management techniques and pond fertilization procedures. The development of a system of pond soil taxonomy can have far reaching implications as an aid in site selection for ponds and predicting the types of soil treatments that will be needed in management.

Identification of the Beneficiaries and Specific Benefits
The beneficiaries of this research are several as follows:

1) The findings will be useful to other investigators working on pond soils. The information will be particularly helpful in the development of an aquaculture soil classification scheme. Data also will be useful in refining pond fertilization techniques.

2) Results of this research will be of importance in expanding the CRSP data base on pond chemistry, and the data will be useful to the development of the global model by the data synthesis team.

3) The findings will be of immediate benefit to pond aquaculturists in host countries, because soil management is a critical issue in pond aquaculture.

4) Ultimately, the data will be used in formulation of pond soil management procedures that will be helpful to US aquaculturists.

Collaborative Arrangements
Other PD/A CRSP researchers are aware of this work unit and that part of it must be conducted at the Core Sites. Dr. C.W. Wood of the Department of Agronomy and Soils at Auburn University is agreeable to collaborate on this subcontract for another year.

Linkages in host countries will involve close cooperation between the resident CRSP investigator and host country counterparts. The PIs have other projects on pond soils, and results of this study will be supplementary to other findings. One PI (Boyd) has close contacts with researchers and commercial aquaculturists in many nations, and his network will be very valuable in disseminating the results of the CRSP effort on pond soils.

Experimental Design
Sites: Honduras (freshwater and brackishwater sites), Thailand, Kenya, and Peru.

Pond Facilities: Three ponds at each site.

Culture Period: N/A

Stocking Rates: Ponds stocked for other experiments will be used. We will select ponds that are in fertilization experiments at the time of sampling.

Water Management: Static ponds for freshwater. Water exchange at 5-10% pond volume per day for brackishwater.

Other Inputs: Fertilization. If liming is used, it is acceptable.

Test Species: We will not be concerned with species, but we prefer tilapia for freshwater ponds and shrimp for brackishwater ponds.

Sampling Plan: In fall 1997, the PIs will travel to the Peru site and collect core samples from three ponds used in the PD/A CRSP effort. Boyd will be in Thailand in January 1998 for purposes unrelated to the CRSP effort, but he will have time to spend 3 or 4 days collecting and processing samples from six ponds at AIT. We will have Karen Veverica collect samples of soil from three ponds at the Kenya site in January 1998 and ship them to Auburn University. Boyd will likely travel to Honduras in early 1998 related to other work, and while there, collect samples from three ponds at both freshwater and brackishwater sites. If not, we will ask Bart Green to collect the samples and ship them to Auburn university.

The soil cores for the Peru site 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 the 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). These core segments will be analyzed (see below) and an evaluation of the data will reveal the depth of soil to be used in future sampling.

Core samples were taken from CRSP sites in Thailand and Honduras in early 1997, and core samples will be obtained at the Kenya site in August 1997. Analysis of data from the core samples in Thailand and Honduras and previous studies on cores from ponds in Alabama (USA) and Egypt (Munsiri et al. 1995, 1996) 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. Therefore, for the second year of sampling at the Thailand, Honduras, and Kenya sites, only the upper 4 cm layers will be sampled. The same ponds from which the initial cores were extracted 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 degrees C, and carried or shipped to Auburn University for analysis.

The Pond Dynamics/Aquaculture CRSP is funded under USAID Grant No. LAG-G-00-96-90015-00 and by the participating US and Host Country institutions. Questions for or about the Aquaculture CRSP? Comments about this site? Email ACRSP@oregonstate.edu.

Disclaimers