Effect of withholding water at different growth stages on the flooded rice yield

Abstract

Two field experiments were carried out in an attempt to determine critical periods for water stress during the growth cycle of flooded rice. Two varieties viz. IAC 435 and IR 841-63-5-L-9-33 were used in this study. Water was withheld at five growth stages: germination totillering, tillering to primordial differentiation, primordial differentiation to flowering, flowering to mil k stage and milk stage to ripening. Yields of these treatments were compared with that of continuous irrigation. There was no interaction between varieties and treatments in which water was withheld. The grain yield and the number of panicles/m² were higher in the variety IR 841-63-5-L-9-33 than in IAC 435. However, the number of filled grains/panicle and the 100 grains weight were higher in the variety IAC 435. Withholding water from the primordial differentiation to the flowering stage decreased the number of panicles/m² and showed a tendency to decrease the grains weight, thereby decreasing the grain yield. Rice varieties also showed sensitivity to lack of water from the flowering to the milk stage, exhibiting a reduction in the number of panicles/m² due to water suppression during that period. Withholding water from the tillering to the primordial differentiation stage increased the number of panicles/m², resulting in the increase of grain yield. Additionally, the results indicated that water is not essential to rice crop after milk stage.