Potential of broadcasting seedlings for making savings in seed, water and labour in irrigated rice production systems in Sri Lanka

摘要

Rice is the staple food of the majority of people in Sri Lanka and annual consumption is about 100 kg per capita. The total land area of the country is about 6.84 million ha, of which about 25 percent is used for agriculture. Rice is grown on about 720 000 ha, of which 550 000 ha are cultivated during the wet season (Oct.-Feb.) and 310 000 ha during the dry season (Mar.-Sept). Sri Lanka may be divided into three major agro-ecological zones on the basis of annual rainfall:dry zone (<1 400 mm); intermediate zone (1 400-2 500 mm); wet zone (>2 500 mm). The dry and intermediate zones are the major ricegrowing areas with, respectively, 63 and 19 percent of total production. Approximately 80 percent of rice is irrigated-55 percent in major irrigation schemes (> 80 ha with tank/reservoir resources) and 25 percent in minor (< 80 ha). The remaining 20 percent is rainfed. (Abeysiriwardena, 2000). Most farmers in major irrigation schemes prefer to cultivate high-yielding and high-quality rice varieties that mature around 120 days. However, the irrigation authorities in Sri Lanka are currently encouraging rice farmers to cultivate varieties with short-maturity duration (i.e. 90-105 days) for a more equitable division of the resources, guaranteeing water supply to all farmers throughout the cropping season. When there is sufficient water in the reservoirs, however, the authorities will release water for 120-150-day cropping, enabling the cultivation also of long-duration varieties.