Effects of seedbed management and delayed transplanting of rice seedlings on crop performance, grain yield, and water productivity

- Transplanting of older but healthy seedlings increases water productivity in rice.
- Seedling competition in seedbed affects total crop duration with late transplanting.
- A 10-days delay in transplanting resulted in an additional 5-6 days in the main field.
- Lower seedbed seeding rate of 25 g seeds m−2 improves yields of older seedlings.
- Seedlings from seedbed with N application produce better yields than without N.

Transplanting older rice seedlings grown in well-managed nursery seedbeds may reduce water input and increase the water productivity of rice. Experiments with a split-split-plot design were conducted at IRRI and PhilRice experiment stations in the 2009 DS, 2009 WS, and 2010 DS to assess the performance of rice in terms of crop growth, grain yield, water input, and water productivity as affected by seedbed management variables such as (1) seedbed seeding rate (SR), (2) seedling age (SA), and (3) seedbed fertilizer management (F). SR was 25 g m−2 (SR25) and 100 g m−2 (SR100) in 2009, and 25 g m−2 (SR25) and 12.5 g m−2 (SR12.5) in 2010. The three SA treatments tested (SA10: 10 days old, SA20: 20 days old, and SA30: 30 days old) were the same in both years, while the F treatments were zero fertilizer (F0), basal fertilizer only (F1), and basal fertilizer + N topdressing (F2). In 2010, the F0 treatment was replaced with higher N-rate application F3 (basal + doubling the amount of fertilizer N for topdressing in F2). Seedling competition in the seedbed affected total crop duration with late transplanting. After 16 days after sowing (DAS) under high seedbed SR and after 21 DAS under low SR, a 10-days delay in transplanting resulted in an additional 5-6 days in the main field. SA significantly affected grain yield, total water input, and total water productivity. The oldest seedlings (SA30) consistently resulted in lower yield, but required the lowest water input, and thus resulted in comparable or even better total water productivity in the two dry seasons. SA20 was found to be the critical seedling age. When SA ≤ SA20, yield was not affected; when SA > SA20, yield was reduced. Lower SR improved the grain yield of SA30 during the DS. Well-fertilized seedbeds have better grain yield than with non-fertilized seedbeds in the DS, even with a higher seeding rate. Lowering seeding density (from 25 g seeds m−2 to 12.5 g seeds m−2) and increasing N topdressing did not enhance grain yield.