Vegetative Growth Stages
The production of an adequate number of tillers is an important factor in rice
yields. Immediately after transplanting, sufficient water should be provided to
facilitate early rooting. Following the early rooting stage, a shallow water depth
facilitates tiller production and promotes firm root anchorage in the soil.
Excessive water at this stage seriously hampers rooting and decreases tiller
production. Leaf blades and leaf sheaths of the submerged plants become weak,
turn light green, and break easily.
Reproductive Growth Stage
Reproductive growth starts when maximum tiller production is completed and
includes the panicle primordia development, booting, heading, and flowering
stages. A large amount of water is consumed in the major part of the reproductive
growth period, which explains why rice is sensitive to moisture stress during
reproductive growth.
Two factors should be considered for water management at this stage. Drought
at this stage causes severe damage, particularly when it occurs from panicle
initiation to flowering stages. Increased panicle sterility, caused by impeded
panicle formation, heading, flowering, or fertilization, occurs if sufficient
moisture is not provided.
The other factor is excessive water at the reproductive stage, particularly at the
booting stage, which causes decrease in culm strength and increases lodging