Rice is grown on a wider range of soils than any other major crop. Deepwater rice, however, is mainly restricted to the level or slightly undulating floodplains and deltas, which are seasonally flooded for 3–6 mo. More than 90 per cent of the deltaic soils of Asia are basically suitable for rice, as they are weakly aerated, have slow permeability and capillary rise, have poor structure and are often underlain by a plough pan (NDDT, 1974a). The soils are of various ages and are usually complex and diverse, particularly in river floodplain areas. Many of these alluvial sediments have undergone little soil formation; their texture varies from medium to fine and is usually more coarse on natural levees and finer in the depressions and backswamps. Prolonged flooding causes profound chemical changes in the soil, most of which are beneficial, and renders the physical properties and tilth of lesser importance. Although many deep-water rice soils are fertile, several types of adverse soils occur.
KeywordsPeat Soil Mekong Delta Floodplain Soil Rice Soil Acid Sulphate Soil
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