Answer:
Asia is noted for several plantation cash crops, of which the most important are tea, rubber, palm oil, coconuts, and sugarcane. Jute, a commercial fibre, though it has decreased in significance, remains a major export crop of Bangladesh. By far the greater part of Asia remains uncultivated, primarily because climatic and soil conditions are unfavourable. Conversely, in the best growing areas an extraordinarily intensive agriculture is practiced, made possible by irrigating the alluvial soils of the great river deltas and valleys. Of the principal crops cultivated, rice, sugarcane, and, in Central Asia, sugar beets require the most water. Legumes, root crops, and cereals other than rice can be grown even on land watered only by natural precipitation.
The traditional method of irrigation in Asia is by gravity water flow. The water from upstream storage reservoirs or diversion dams is carried through canals to field distributaries. In some systems the fields adjoin one another, and the water is able to flow from one field to the next; it may, however, take some time for the water to move across the fields back to the canal system. The disadvantages of this system include water loss by evaporation and seepage and the possibility that the continuously flowing water will carry with it soil nutrients, fertilizers, and pesticides. In Japan and Taiwan water is moved by small electric pumps, which operate continuously during the growing seasons.
