Effects of Foliar and Soil Application of Gibberellic Acid (GA3) at Different Growth Stages on Agronomic Traits and Yield of Rice (Oryza sativa L.)

Use of Gibberellic acid (GA3) application in rice cultivation for increasing the grain yield is well documented. However, improper and untimely use of GA3 could result in poor response to GA3 application. This study was aimed at to investigate the timing of application during different growth stages and mode of application of GA3 on the growth and yield of MR219, a popular Indica rice variety, released by Malaysian Agricultural Research and Development Institute (MARDI). Two commercial GA3 formulations, namely ProGibb SG containing 40% GA3 and ProGibb silica Granule containing 0.1% GA3 were used for foliar and soil application, respectively. GA3 was applied at late tillering stage and at 10-30% panicle heading stage. Interestingly, GA3 application as foliar spray during the early reproductive stage, ie at 10-30% panicle heading stage enhanced the grain yield significantly, recording over 27% grain yield increase over the untreated control. Moreover, two applications of GA3 at 7 days’ interval has consistently given higher grain yield than single application. However, there is no significant difference in flag leaf characteristics, one thousand grain weight and milling qualities among different treatments. Our study has clearly illustrated that foliar application of GA3 at weekly interval at 10-30% panicle heading stage, can increase rice grain yield significantly.