Effects of Different Irrigation Water Sources Contaminated with Heavy Metals on Seed Germination and Seedling Growth of Different Field Crops

Irrigation water quality is of critical importance for optimum crop yield of economically important field crops in the Kahramanmaraş plains. A preliminary ecotoxicological assessment is necessary before large-scale irrigation. Therefore, this study aims to evaluate the quality of irrigation water supplied from different water sources (Karasu, Erkenez, and Oklu streams on the Aksu River and Sır Dam) and the effects on the seed germination and early seedling growth of different field crops (wheat, alfalfa, ryegrass, and maize) irrigated with this water. For this, in order to evaluate the effects on seed germination and early growth parameters of forage crop seedlings, a Petri dish germination test was carried out with four replications using a completely randomized design (CRD). Before the germination assay, heavy metal concentrations including copper (Cu), iron (Fe), lead (Pb), chromium (Cr), arsenic (As), nickel (Ni), and cadmium (Cd) were analyzed in water samples obtained from different water sources. In all water samples used for the experiment, Cu concentrations exceeded the acceptable limit of 0.2 mg L⁻1. The Cu levels found were 0.98 mg L⁻1 in Karasu (KC), 1.627 mg L⁻1 in Oklu (OC), 0.945 mg L⁻1 in Erkenez (EC), and 1.218 mg L⁻1 in Sır Dam (SD) waters. Additionally, Fe exceeded the limit only in KC, while Cd surpassed the permissible levels in EC and SD water samples. Seeds exposed to different water treatments were germinated in a climate chamber at 20 ± 1 °C. Over two weeks, daily germination and seedling growth parameters were measured. The results indicated that higher heavy metal concentrations in irrigation water led to a decline in seed germination rates and adversely impacted early seedling growth. Notably, water from Karasu Creek exhibited the most significant negative impact on all germination and growth parameters in the tested crops, especially due to Cu and Fe metal toxicity. Additionally, ryegrass seeds were most affected by these irrigation waters. This study highlights the importance of using uncontaminated quality irrigation water for optimal crop production by quantifying its impact, such as the percentage of decrease in germination or seedling growth.