Crop growth rate (CGR), root length, panicle length and grain yield of rice (Oryza sativa L.) as influenced by gibberellic acid

Field investigations were carried out at the Experimental Farm, Department of Agronomy, Faculty of Agriculture, Annamalai University during early samba (2013) and thaladi (2014) to study the crop growth rate, root length, panicle length and grain yield of rice (Oryza sativa L.) as influenced by gibberellic acid. The experiments comprised of seven treatments viz., T1 - Gibberellic acid @ 5 g ha-1, T2 - Gibberellic acid @ 10 g ha-1, T3 - Gibberellic acid @ 15 g ha-1, T4 - Gibberellic acid @ 20 g ha-1, T5 - Gibberellic acid @ 25 g ha-1, T6 - Triacontanol 0.05% EC @ 250 ml ha-1 and T7 - Control. The treatments were conducted in randomized block design (RBD) and replicated thrice. Rice variety BPT 5204 was used as test variety in both the seasons of study. The crop growth rate (CGR), root length, number of tillers m-2 and panicle length were strikingly impressive by Gibberellic acid @ 25 g ha-1 in both seasons. Among the different treatments, Gibberellic acid @ 25 g ha-1 recorded the higher grain yield. This was followed by Gibberellic acid @ 20 g ha-1. Triacontanol 0.05% EC @ 250 ml ha-1 and Gibberellic acid @ 10 g ha-1 were next in order and were on par in their values. The lowest grain yield was recorded in control (no foliar spray). Based on the above experimental results, it could be concluded that cultivation of rice with foliar application of Gibberellic acid @ 25 g ha-1 significantly registered higher crop growth rate (CGR), tillers number m-2, root and panicle length and grain yield. The dosage of Gibberellic acid @ 25 g ha-1 was found to be an agronomically sound and ecologically safe practice for augmenting higher productivity of rice.