Effect of Plant growth Regulators on Lodging and Yield of Broadcast Seeded Flooded rice at different Seding Rates

Abstract

field experiment was conducted at the International Rice Research Institute (IRRI), Philippines during the 1989 dry season. A split plot design with two-factor factorial (varieties x seeding rates) main plot and single factor (plant growth regulators) subplot with three replications was used. Plots (3x5m) were constructed and leveled before pregerminated seeds were sown. Fertilizer N was applied as 9 kg N/rai at 15 days after broadcasting and 9 kg N/rai topdressed at 5-7 days before panicle initiation using prilled urea (46-0-0). Results showed that plant growth regulator HOE-785-03P03 slightly controlled lodging of brodacast seeded flooded rice, whereas paclobutrazol and inabenfide effectively controlled lodging and reduced plant height but did not significantly increase rice grain yield. IR68 was more susceptible to lodging and had lower bending resistance and elasticity index than IR72. seeding rate at 16 kg/rai appeared to be the optimum seeding rate for broadcast seeded flooded rice because no yield advantage was observed when the rate was increased from 16 to 32 kg/rai.