Effect of different doses of urea on the uptake of cadmium from soil by Brassica napus: A case study in Sargodha, Pakistan
The present investigation was conducted to study the effect of different doses of urea on cadmium uptake by canola (Brassica napus L.) applied in full and split doses. Nine different treatments of urea used were: 0 (control), 60, 90, 120 and 150 kg/ha applied to soil as full doses before sowing, and 60, 90, 120, and 150 kg/ha applied as two equal splits; the first was before sowing, while the second was before flower initiation. Samples of soil were taken just after mixing the appropriate dose of urea, whereas those of stems and leaves were taken at the vegetative stage. Cadmium (Cd) concentrations in soil, stems and leaves samples were determined unconnectedly. Based on the data recorded, it was concluded that all the treatments had significant effect on Cd concentrations in soil, leaves, stems, roots and pods. The mean Cd value in soil, leaves and stem ranged from 0.84 to 1.33, 0.32 to 1.07 and 1.27 to 1.69 mg kg-1 dry weight, respectively. While in roots and pods, Cd concentration varied from 1.31 to 1.77 and 1.05 to 1.36 mg kg-1, respectively. The mean Cd level in soil and plant body was much lower than the critical level reported by different researchers, thus an additional supplementation of Cd is required to meet the needs of plants. Mineral supplements with rational amount of Cd sources are suggested to avoid complications caused by Cd deficiency as well as to achieve an optimal animal production of ruminants being reared on the pasture.
Key words: Brassica, cadmium, forage, soil, Pakistan