The Effect of Sustained Deficit Irrigation and Different Irrigation Methods on Yield and Evapotranspiration of Second-Crop Soybeans in the Mediterranean Basin

Soybeans are a crucial major food source in human and animal nutrition due to their high fat and protein content. This study investigated the effects of different irrigation methods on yield and yield components of second-crop soybeans under deficit irrigation conditions. The study aimed to determine the crop evapotranspiration, water productivity (WP), and irrigation water productivity (IWP) of the second crop soybean. The study followed a split plot random block experimental design with three replications. The main treatments of the study were subsurface drip irrigation (SDI), drip irrigation (DI), and furrow irrigation (FI) with four different water application levels (100%, 75%, 50%, and 25%) serving as subtreatments. Crop evapotranspiration (ETc) ranged between 236-482 mm for DI, 185-410 mm for SDI, and 275-562 mm for FI during 2018 and 2019. The yields for DI, SDI, and FI varied between 3,340-4,030 kg ha(-1), 3,250-3,780 kg ha(-1), and 2,800-3,680 kg ha(-1) during 2018 and 2019, respectively. The effect of water deficit applications on yield was statistically significant at p<0.05 level. It was determined that the yield components of soybeans were negatively affected by deficit irrigation treatments, but the effect of different irrigation methods was not significant. There was no statistical difference between the treatment with 25% deficit irrigation and the full irrigation comparing the yield and yield components of the study. Moreover, WP and IWP values increased as the amount of irrigation water decreased in all irrigation methods. Thus, a 25% deficit is recommended as an alternative to full irrigation in the Mediterranean Basin when water resources are scarce. (c) 2024 American Society of Civil Engineers.