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

Abstract 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 (SR 25 ) and 100 g m −2 (SR 100 ) in 2009, and 25 g m −2 (SR 25 ) and 12.5 g m −2 (SR 12.5 ) in 2010. The three SA treatments tested (SA 10 : 10 days old, SA 20 : 20 days old, and SA 30 : 30 days old) were the same in both years, while the F treatments were zero fertilizer ( F 0 ), basal fertilizer only ( F 1 ), and basal fertilizer + N topdressing ( F 2 ). In 2010, the F 0 treatment was replaced with higher N-rate application F 3 (basal + doubling the amount of fertilizer N for topdressing in F 2 ). 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 (SA 30 ) 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. SA 20 was found to be the critical seedling age. When SA ≤ SA 20 , yield was not affected; when SA > SA 20 , yield was reduced. Lower SR improved the grain yield of SA 30 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.