Nitrogen fertilizer management for tidal submergence tolerant landrace rice (Oryza sativa L.) cultivars

In tidal submergence ecosystem, nitrogen (N) is a crucial nutrient for improved and sustainable rice production. Therefore, a series of on-farm and on-station field experiments were conducted to develop a suitable N management practice for tidal submergence tolerant landrace aman rice. In on-farm, urea deep placement (UDP) through urea super granule before panicle initiation (PI) stage was compared with no fertilizer application. Similarly, five N fertilizer management practices viz. (i). two splits of prilled urea (PU), (ii). UDP at 10 DAT, (iii). UDP before PI, (iv). full dose PU before PI and (v). No urea (control) were compared at on-station trial. Tidal submergence tolerance aman rice varieties (Rajashail, Kutiagni, Sadamota and Lalmota) were used as testing materials. In on farm experiment, aman cultivars produced 2.0-2.5 t ha−1 grain without N fertilizer. But, cultivated Rajashail, Kutiagni, Sadachikon, Sadapajam, Lalmota and Sadamota gave 3.0-3.5 t ha−1 grain yield with the UDP before PI in tidal prone areas. Though UDP required fertilizer and application cost but it gave profit upto 22,000 BDT ha−1 (Bangladeshi Taka). In on-station experiment, UDP before PI stage significantly increased rice yield and economic return although it was comparable to two splits of PU and top dressing of PU before PI stage. However, UDP at 10 DAT increased straw yield but failed to increase grain yield even compared to control. It could be concluded that UDP before PI stage of rice is an effective method for increasing rice yield and farm income in tidal prone areas.