*2.3. Seedbed Management*

Seedlings used in the experiment were grown in the seedbed adjacent to the experimental field. Three well-puddled seedbed plots were prepared with one seedbed plot for each variety used. Each plot was equally divided into four divisions for the different seedling ages. To raise healthy and

vigorous seedlings in the seedbed, seeding rate and fertilizer management recommendations from [14] were used. Basal fertilizer was applied (2 g N + 3gP + 2gKm−2) in the seedbed using complete fertilizer (14–14–14). After testing for germination rate, the pregerminated seeds of the three varieties were carefully sown in the seedbeds separately by variety at a uniform seeding rate of 25 g m<sup>−</sup>2. After sowing, the seedbeds were kept wet all the time to avoid hardening of the soil, which may damage seedling roots when pulled out. The seedbeds were flooded as seedling height increased. Seedlings were carefully hand-pulled 1 d before transplanting, and the pulled seedlings with intact roots were placed in plastic trays with water. Only needed seedlings were hand-pulled for specific seedling age treatments. Seedbeds were continuously managed until the transplanting of the last seedling age treatment (SA45) in the main field was completed.
