Effects of Atonic Concentration and Application Stage on Grain Yield and Yield Components of Sorghum bicolor (L.) Moench

Abstract

Background: Improving grain yield and its components is a major objective in sorghum production, particularly under arid and semi-arid conditions where crop productivity is frequently constrained. The application of plant growth regulators such as Atonic can promote plant development and productivity through their positive effects on plant physiological functions. This study evaluated the effects of different Atonic concentrations and application stages on grain yield and yield components of sorghum. Methods: Field experiments were conducted during the spring and autumn growing seasons of 2021 at the University of Anbar, Iraq. Treatments consisted of four Atonic concentrations (0, 2.5, 5.0- and 7.5-mL L-1) applied at three growth stages (end of vegetative growth, booting and 50% flowering) using a split-plot arrangement within a randomized complete block design with three replications. Data were collected on grain-filling duration, 1000-grain weight, grain number per head, grain yield and harvest index. Results: Atonic concentration significantly affected grain-filling duration, 1000-grain weight, grain number per head, grain yield and harvest index in both growing seasons. The highest values for most yield traits were obtained at 5.0- and 7.5-mL L-1. Spraying at the end of vegetative growth and booting stages generally produced superior results compared with spraying at 50% flowering. Significant interaction effects between Atonic concentration and application stage were observed for several measured traits. Foliar application of Atonic, particularly at 5.0-7.5 mL L-1 during the end of vegetative growth stage, improved grain yield and most yield components of sorghum under the environmental conditions of western Iraq.