Variation in quality parameters of second crop soybean under different irrigation methods and deficit irrigation conditions

This study was conducted during the 2018 and 2019 growing seasons at the International Agricultural Research and Training Center in Izmir, T & uuml;rkiye, to investigate the effects of different irrigation methods and irrigation water levels on oil content, protein content, and fatty acid composition in second-crop soybean cultivation. The experiment was arranged in a randomized block split-plot design with three replications. The irrigation water level significantly affected protein, oleic acid, and linolenic acid contents in 2018 (p < 0.05), and oil content, palmitic acid, oleic acid, linoleic acid, and linolenic acid in 2019 (p < 0.05). Additionally, highly significant effects (p < 0.01) were observed on oil content, palmitic acid, linoleic acid, and stearic acid in 2018, and on protein and stearic acid in 2019. The highest protein content (35.66 %) was recorded under full irrigation with the furrow method, while the lowest (31.07 %) was found under 75 % deficit irrigation with subsurface drip in 2018. Conversely, the highest oil content (21.21 %) was observed under 75 % deficit irrigation with subsurface drip, and the lowest (19.32 %) under 25 % deficit irrigation with drip irrigation. Linoleic acid, linolenic acid, and palmitic acid contents were highest under full irrigation, whereas oleic and stearic acids peaked under 75 % deficit irrigation. These findings highlight the significant influence of both irrigation method and deficit level on soybean seed quality, particularly oil and protein composition.