Methods for Extending Rice Seedling Age and Key Points for Preparing to Transplant Rice While Waiting for Rain as a Drought-Resistance Measure

In a normal year, the seedling age for machine-transplanted rice is about 30 days, about 40 days for seedling-throwing rice, and about 50 days for water-raised seedlings. If the water for transplanting comes late, the seedling age must be extended to more than 60 days in order to wait for water before transplanting.

First, sow sparsely to cultivate strong seedlings of extended age. That is, by expanding the area of the seedling-raising bed and reducing the sowing rate per square meter, the tillering-stagnation period of the seedlings is prolonged, which can effectively increase the seedling-age flexibility of seedlings sown early at the proper time and improve seedling quality; this can both raise per-unit yield and resolve the contradiction of having no water for transplanting in the early period. The sparser the sowing, the greater the seedling-age flexibility. If other management measures are well coordinated, the seedling age of dry-raised seedlings can exceed 70 days.

Second, use chemical regulation to extend seedling age. On the basis of dry raising and sparse sowing, from the 3-leaf stage onward, spray paclobutrazol 1 to 2 times in split applications; for each mu of seedling field, use 15% paclobutrazol wettable powder mixed with 50 kg of water (in principle at a concentration of 150 PPM) and spray evenly to promote tillering and control growth; when applying, there should be no water on the bed surface, and water should be irrigated onto the bed the next day after application. Under the same conditions, the seedling age can be extended by more than 10 days.

Third, raise seedlings by two-stage temporary transplanting. For seedling beds sown at the normal sowing time and at a relatively high sowing rate, if transplanting must wait for water and the seedling age must exceed 60 days, two-stage temporary transplanting should be used to extend the seedling age. When the seedlings grow to the 2-leaf 1-heart stage, temporarily transplant them at a row spacing of 6-10 cm and a hill spacing of 5-8 cm. Two to three days after temporary transplanting, for each mu of seedling field, spray 15% paclobutrazol by the same method described above; if the seedling age is to exceed 70 days, then after 15 days apply paclobutrazol once more by the same method, to cultivate strong multi-tillering seedlings of extended age.