The Effect of Soil and Foliar Nitrogen Applications On Cd Toxicity of Durum Wheat (Triticum turgidum L.) Grown in Low and High Cadmium Contaminated Soils

A pot experiment was conducted in the greenhouse condition to investigate Cd tolerance of wheat in cadmium containing soils (0.5 and 5.0 mg Cd kg-1), taking into account the effect of N fertilization. The study investigates the effect of N application and foliar application of urea on cadmium uptake and accumulation in durum wheat and evaluates its effects on physicochemical properties. The results of this study showed a very significant positive correlation between increasing plant Cd concentration and increasing N supply. That an adequate amount of CaNO3- fertilizer in the soil together with foliar application of urea statistically increased plant biomass of durum wheat and in parallel increased Cd accumulation. In terms of plant biomass, the increase in very low nitrogen (50 mg N kg-1) application (S1) to the (0.5 mg Cd kg-1) contaminated soil application was 187.70%, and 259.09% for Sufficient nitrogen (200 mg N kg-1) application (S2) to the (0.5 mg Cd kg-1) contaminated soil, when compared to the No nitrogen application (SC) to the soil (Control) application. Upon foliar urea application, increases were recorded as 90.78% for Foliar application with urea only, no nitrogen applied (FC) to soil, 216.57% for Foliar urea with very low nitrogen application (F1) to the soil (50 mg N kg-1), and 298.01% for Foliar urea with sufficient nitrogen application (F2) to the soil (200 mg N kg-1) compared to SC. Similarly, Cd concentration in durum wheat increased with higher nitrogen application, with increases observed as 16.93% for S1, 42.28% for S2, 26.14% for FC, 34.65% for F1, and 58.11% for F2 compared to SC. Consequently, it was also the foliar application of urea together with the supply of nitrate that increased the bioavailability of Cd and decreased its toxic effect. The amount of N fertilizer not only promotes plant growth and increases plant biomass, but also increases the accumulation of Cd in the shoot.