Respons varietas padi terhadap perendaman, pemupukan, dan jarak tanam

إنجليزي. Combinations of fertilizer application and plant spacing on submergence tolerant rice varieties are expected to reduce yield losses and increase grain yields in the submerged flood-prone wetland. The research was aimed to determine the effect of submergence on growths and yields of rice, to find suitable technique of fertilizer application, and the best plant spacing in a flash flooding wetland. The research was conducted at farmer's field in Langgengsari village, Belanakan District, Subang Regency, West Java, during the wet season of 2010. The treatments were arranged in a split-split plot design with three replications Fertilizer application methods (Briquette Urea 90 kg N/ha versus Phonska + urea 90 kg N/ha) was the main plots

planting methods [equal spacing (20 cm x 20 cm) and legowo 6:1 (20 cm-40 cm) x 10 cm)] as sub-plots, and submergence tolerant rice varieties (IR64 Sub-t, Swarna Sub-1 dan Inpara 3) as sub-sub plots. The results showed that upon plant submergence for 14 days at the vegetative phase (14 to 28 OAT), the tolerant varieties still survived until harvest. During the 14-day submergence, plant height increased between 1.74 cm (Inpara 4) and 2.70 cm (lnpara 3), tiller number per hill increased between 0 (Inpara 3) and 3 (Inpara 5). Application of prilled urea + Phonska three times during the plant growth resulted in higher yield (4.99 t dry grain/ha) significantly more than that applied with briquette urea twice (4.12 t dry grain/ha), indicating the importance of the third N application at primordial stage. The submergence tolerant rice varieties (lnpara 4 and Inpara 5) produced significantly higher yields (4.83 t and 4.80 t dry grain/ha, respectively) than Inpara 3 (4.04 t dry grain/ha) or Ciherang (3.90 t dry grain/ha) that were grown by farmers in the surrounding areas. The best plant spacing for rice in the flood prone lowland area varied with the rice varieties. Paired rows (jajar legowo) 6:1 planting method was more suitable for Inpara 5 (5.22 t dry grain/ha) than the squared spacing (tegel) 20 cm x 20 cm (4.38 t dry grain/ha). Meanwhile, the tegel spacing was better for Inpara 4 (5.29 t dry grain/ha) than the jajar legowo 6:1 (4.36 t GKG/ha). The yield of Inpara 3 was not affected by plant spacing treatment.