Title : Effects of trinexapac-ethyl in combination with nitrogen fertilizer on growth and yield of three rice varieties
Lodging is a problem that reduces rice yields. Application of excess nitrogen fertilizer is one factor contributing to rice lodging. Trinexapac-ethyl is a plant growth regulator that reduces stem elongation and helps strengthen cell walls, so it can improve yield and reduce the likelihood of lodging. The objective of this research was to find the optimum rate of nitrogen fertilizer to use together with trinexapac-ethyl foliar spray on 3 different rice varieties. The experiment was a split plot in RCB. The main plot was the 3 rice varieties: Pathum Thani 1, Pathum Thani 80 and Pathum Thani 200. The sub plot was 4 rates of nitrogen fertilizer application: 0, 62.5, 125, and 187.5 kg/ha. Trinexapac- ethyl foliar spray was applied at a concentration of 100 ppm two times, at 25-30 days and at 45-50 days after planting, at the same time as nitrogen fertilizer was applied. The results showed that plant height, chlorophyll content, leaf area, internode length, panicles numbers, and seed numbers were not significantly different between the 3 rice varieties under trinexapac-ethyl treatment combined with nitrogen fertilizer application at the above concentrations, but statistically significant differences were noted in yield, 1,000-grain weight, filled grain percentage, harvest index, cellulose content and lignin content. Application of nitrogen fertilizer at different rates resulted in statistically significant differences in plant height, chlorophyll content, internode length, yield, panicles numbers, harvest index, and cellulose content but did not cause statistically significant differences in leaf area, seed numbers per panicle, 1,000-grain weight, filled grain percentage and lignin content. From these results we can conclude that spraying trinexapac-ethyl 100 ppm two times at seedling stage (25-30 days old) and at tillering stage (45-50 days old) together with nitrogen fertilizer at the rate of 125 kg/ha resulted in the highest yield.