RICE

Rice (Oryza sativa) production systems differ significantly in different parts of the world. Most rice is irrigated although in some areas upland rice may be grown in areas of high rainfall. In the flood deltas in Asia, rice is grown at sea level, but in the Himalayas some rice is grown at 3000-m altitude. In the USA, rice may be sown with pre-germinated seed dropped into standing water and subsequently treated with fertiliser and pesticides by aircraft in contrast to the manual treatments on small farms in Asia, where traditionally young plants were raised in seedbeds and transplanted when 15–25 cm high into rows 15–30 cm apart. This method of transplanting and flooding fields provided excellent cultural weed management. However, with movement of labour to urban areas and the costs of transplanting increasing, more farmers are now broadcasting seeds directly into the rice paddies (Heinrichs et al., 1987). This has increased the problems of weed management and led to an increased use of herbicides to combat yield losses that may reach 50%. Pesticide inputs are highest in Japan, where most rice growers have other full-time employment…