Field crops such as wheat, alfalfa, ryegrass, and corn play a vital role in agriculture and livestock production, particularly in the Kahramanmaras plain, irrigated by the Aksu River and the Sır Dam. Given the critical importance of irrigation water quality for optimal crop production, this study aimed to assess the impact of Karasu, Erkenez, and Oklu creeks on the water quality of the Aksu River and Sır Dam, and its subsequent effects on the germination and seedling growth of key field crop species grown in the region. The experiment was conducted in 2017 at the Field Crops Laboratory, Faculty of Agriculture, Kahramanmaras Sutcu Imam University, Turkey, using a completely randomized design (CRD) with four replications. Seeds were germinated using water samples collected from various locations within the dam basin, with tap water serving as the control. Before germination, the water samples were analyzed for concentrations of heavy metals, including copper (Cu), iron (Fe), lead (Pb), chromium (Cr), arsenic (As), nickel (Ni), and cadmium (Cd). Seeds exposed to different water treatments were germinated in a climate chamber at 20 ± 1°C. Over two weeks, daily germination counts were recorded, and at the end of the experiment, total germination and seedling growth were measured. The results demonstrated that irrigation water contaminated with heavy metals significantly affected seed germination and seedling growth. Notably, water from Karasu Creek exhibited the most pronounced negative impact on all germination and growth parameters in the tested crops.