Webpages with more general information
Webpages with more detailed information.
Rice Yields vary with physical conditions. Most of the developed swampland is found along the sweet water, tidal river sections. Usually yields of 1.5-2.5 tons/ha are obtained with only one harvest per year. In stagnant water conditions with severe acidity, the yields are much lower and often the land is abandoned. Traditionally the best yields are obtained close to the rivers. Here frequent flooding with sweet water may occur during high tide.
Optimum yields of 6 ton/ha and more are found using improved rice varieties in conditions with frequent tidal flooding. In the Telang project (South Sumatra) these yields are also obtained in non-tidal flooded areas. In this project water control structures are installed and more drains at tertiary level are constructed and existing canals are upgraded. Presently two crops per season are possible. A very important factor has been the widely introduced mechanised land preparation in the area. Pump irrigation has been hardly used yet.
Factors influencing the yields are related to factors such as 1) potential for tidal flooding (= potential for irrigation), 2) the land levels related to the mean high tide level during springtide in the adjoining canals (= potential for subsurface supply), and 3) the land levels in relation to the mean water level in the adjoining canals (= the drainage potential expressed in the Effective drainage depth). These three factors determine the potential for water supply and percolation quantities. The severity level of the toxic and acid conditions are related to these water supply and percolation quantities. The less water supply and percolation quantities, the more conditions deteriorate and become very acid and toxic.The depth of occurrence of soil layers with high acidity in acid sulphate soils does not appear very important. It should be realized that beside these potentials for yields, also the maintenance of the main infra-structure and the on-farm water management influences the yields. See also Web page Problems for more information.
Fisheries depend among others on water quality in the rivers and canals. Near the coast there are often potentials for brackish water fisheries such as shrimp and crab farming, but the vast majority of the swamps depends on freshwater fisheries. Freshwater shrimp farming in canals has a good potential in areas nearby large rivers with their main catchment in the uplands. In areas with acid sulphate soils, which release large quantities of acids, this type of shrimp farming is not possible. In this case black fish types can survive a couple of months of extreme acid water and the cultivation in shallow ponds remains viable when for the major part of the year the canal water is non-acid (pH>4.5). The potentials for fisheries is limited in rivers with the main catchment area in peat dome areas (ombrogenous peat soil).
See also WebPage Index.