Effect of foliar application of Ethephon in growth traits, seed yield and it’s components in Alfalfa

Due to the increasing demand for green fodder in Iraq to sustain livestock, alfalfa cultivation primarily focuses on fodder production, while seed yield is deemed of secondary importance. Meeting this demand requires implementing diverse agricultural strategies aimed at enhancing alfalfa seed yield, notably through the application of plant growth regulators (growth retardants). Therefore, this study aims to know the possibility of increasing seed yield and determining the appropriate spraying stage and concentration using the growth inhibitor Ethephon to increase seed yield of the local variety of alfalfa. A field experiment was carried out from October 2021 to the end of August 2022 at the Experimental Field at the College of Agricultural Engineering Sciences, University of Baghdad, Iraq. The main objective of the study was to find out the effect of Ethephon concentrations (0, 250, 500 and 750) mg/L and three stages of foliar application (vegetative growth, beginning appearance of flower buds and 50% flowering) on seed yield and its components of alfalfa local variety. The layout of the experiment was Randomized Complete Block Design (RCBD) arranged in a split plot, with three replications. Foliar application stages were used as main plots while the Ethephon concentrations were used as sub-plots. Spraying of Ethephon at 750 mg/L resulted in a significant increment in the number of stems m^-2, number of ripe racemes per stem, number of pods per raceme, biological yield, seed yield and harvest index. The highest seed yield (550.3 kg/ha) of alfalfa was obtained when plants were sprayed with Ethephon 750 mg/L at vegetative growth, which produces significantly highest number of racemes per stem and number of pods per raceme compared to other concentrations of Ethephon. The mean seed yield amounted to 453.2 kg/ha and it was significantly higher compared to Ethephon concentrations of 0 and 250 mg/L but at par with 750 mg/L concentration of Ethephon.