Mitigating The Effects of Salt Stress on The Growth and Yield of Soybean Cultivars (Glycine Max L.) By Kinetin Foliar Application

This research investigated the effect of salt stress from the use of relatively saline water on the growth and yield of soybean cultivars (Glycine max L.) through foliar application of the growth regulator kinetin. It was conducted at the Field Crop Research Station (FCRS), Field Crop Department, Tikrit University. The experiment employed two types of irrigation water namely river water from the Tigris River and well water of the research station. It also involved two treatments comprising kinetin and without kinetin growth regulator application, and four soybean cultivars, Shaima, Laura, Dee, and Lee. The experiment was applied using a Randomized Complete Block Design with as split-plot arrangement. Three plants were sourced during the soybean growing season from each experimental unit at 30, 60, 90, and 120 days after planting (DAP) to measure leaf area and dry weight to estimate relative growth rates (RGR), crop growth rates (CGR), and net assimilation rates (NAR). Chlorophyll content in the leaves was measured 50 DAP, and at the end of the season, oil percentages and yields were assessed. All studied traits were significantly affected by the quality of irrigation water, the application of the growth regulator kinetin, the soybean cultivars, and the interaction among these factors. For instance, irrigation with well water reduced chlorophyll content, oil percentage, and yield by 15%, 36%, and 17%, respectively compared to river water irrigation. The findings show that the soybean crops in the Salah al-Din (Tikrit City) area which is characterized by gypsum soil, showed weak growth and yield. The use of river water irrigation, the Shaima cultivar, and kinetin did not elevate yield to global production standards