This research was carried out at the Experimental Station Edgardia of the Faculdade de Ciências Agronômicas, Universidade Estadual Paulista (UNESP), Botucatu, State of São Paulo, Brazil, during the growing season of 1990/91. The objective of this study was to evaluate the effects of water depths and the beginning of water application on the rice development and yield. Three water depths (5, 10 and 15 cm) and three water application dates (15, 42 and 74 days after crop emergence) were tested in a randomized complete blocks design, arranged in splitplots. The dates were designed as main plots and the water depths as splitplots. The grain yield was not affected by the water depths. A water admission delay to 74 days after crop emergence reduced the filled grain number and the grain yield and also caused a prolongation of the plant cicle. The water depth of 15 cm reduced the tillering, stem and panicle number. The water application date is the main factor on the reduced grain yield when comparated whith the water depths.
irrigated rice; irrigation management; irrigation by flooding; water depths