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No Thumbnail AvailableBook (series)Brackishwater aquaculture in the tropics: the problem of acid sulfate soils. 32p. 256645-E 1985
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No results found.Brackishwater aquaculture is presently responsible for a relatively minor component of the total fish landings for the world, but is frequently mentioned as offering excellent potential for major expansion. Under the stimulus of the very high international market value of penaeid shrimp, the investment community, both private and public, has become substantially involved in brackishwater shrimp aquaculture projects in tropical countries, especially during the past decade. Experience from field r esearch and private development of shrimp aquaculture in the tropics has been mixed, with some notable failures, especially in the early stages, as well as successes. One major cause of low shrimp and fish productivity in a number of coastal aquaculture projects is the presence of pyrite, a very common iron sulfide mineral in tropical coastal soils and sediments, often associated with mangrove ecosystems. When exposed to air, pyrite in moist soils is oxidized by bacteria to produce iron oxides and sulfuric acid. Sulfuric acid leaches aluminium as well as iron from soil minerals, and the combination of acidic conditions and high concentrations of reactive, toxic metals is destructive to most plants, including rice, as well as fish, and especialy shrimp. The result is chronically low yields of fish and shrimp, and, in the worst cases, extensive kills of the culture organisms immediately following the runoff of acidic water from pond dikes after rainfalls. Some of the acid impacts can b e reduced by extensive soil leaching programmes prior to culturing, and applications of large amounts of lime during growing periods. Eventually the soils will become relatively free of pyrite given sufficient oxidation and leaching. However, the time-scale for effective removal of the pyrite using traditional construction and management schemes can often be decades. From the viewpoint of development programmes, and the repayment of loans acquired on the expection of high yields of valuable prod ucts such as penaeid shrimp, a long period of poor production can easily lead to economic failure of a project. In addition, large-scale conversion of mangrove forests to low productivity aquaculture systems can substantially undermine the ecological basis for shrimp and other capture fisheries in coastal environments. Furthermore, many development schemes involve the rehabilitation of old coastal ponds which, in many cases, imply new design of canals, extensive earth movements and excavations, and hence re-exposure of acid sulfate soil layers, creating a serious problem in areas where soil acidity had long ago ceased to present difficulties. Thus the net result of a major capital investment in aquaculture can be a reduction in the total capture fishery and aquaculture yield of the area concerned. -
No Thumbnail AvailableProjectAquaculture development and coordination programme. Fish feed technology. Lectures presented at the FAO/UNDP Training Course in Fish Feed Technology, Seattle, Washington, 9 October - 15 December 1978 1980
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No results found.The need for developing suitable feeds based on locally available inexpensive ingredients has been widely recognized. Since lack of trained personnel is the main constraint in the development of fish feed technology in developing countries, the FAO/UNDP Aquaculture Development and Coordination Programme (ADCP) organized a special training course in fish feed technology at the College of Fisheries, University of Washington, Seattle, with a view to forming a small corps of fish feed specialists wh o could then be the focal points for future feed development programmes in their respective countries. The first report of the training course was presented in the report ADCP /REP/79/8. This present volume represents the edited texts of lectures presented by different specialists. Some additional material has been included for more complete coverage of the subject. Together, these texts may be considered to constitute a manual on fish feed technology, even though they were not prepared for that purpose. Twenty-six papers are included, under the general headings: (1) Digestion, physiology and anatomy; (2) nutritional bioenergetics; (3) nutritional biochemistry; (4) feedstuffs; (5) feed formulation; (6) feed manufacturing technology; (7) practical diets; and (8) quality control. Appendices include conversion tables, electrical data, and details on pelletability of selective feedstuffs, pellet die specifications, and equipment requirements for an 8 ton an hour feed mill. -
Book (stand-alone)Soil survey investigations for irrigation
FAO Soils Bulletin 42
1979Also available in:
No results found.The pressing need for increased agricultural production in the years ahead can only be met by more efficient use of our land and water resources including more widespread and better irrigation in those regions where rainfall is inadequate. Production gains will be shortlived unless the attendant hazards of salinization, water logging and lowered fertility are kept in check by effective planning and management based on a thorough understanding of the soil conditions. Soil survey and land classifi cation are generally accepted essential preliminaries to investment in irrigation development. This publication aims to describe the special requirements of soil survey for irrigation development, and assumes that the reader is familiar with basic soil science and soil survey techniques.
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