Study of potassium and zinc effects on quantity and quality parameters and grain cadmium content of winter wheat irrigated by waste water

There are a lot of evidence on the effects of potassium and Zinc to increase wheat yield and improving seed quality and reducing of cadmium uptake by plant. An investigation carried out to study the effects of these two elements in the process of Cd uptake by wheat and effects of these elements in other growth parameters. The statistical design was split plot with three main factors (without potassium، potassium consumption based on soil test potassium and potassium consumption tow time more than soil test potassium) and four sub plots (control Zn، soil Zn consumption، foliar Zn application and، Zn in Soil and consumption combined with foliar application). The experiment was done in a wheat field in southern of Tehran، which many years were irrigated with wastewater. The results of experiment showed that the main effects (potassium effects) on grain yield، straw yield، spike length، number of grains per panicle and grain weight is significant. The above characteristics increased by use of potassium based on soil test recommendation significantly and extra use of potassium did not any effects on these parameters. Secondary effects (Zn) on the above traits were significant. Grain yield، straw yield and grain weight were not affected by different methods of Zn application، but combined use of Zn as soil application and foliar، produced the greatest amount of panicle length and number of seeds per ear. The main effects of zinc and potassium was significant on the concentration of mean grain cadmium. Consumption of these elements significantly reduced grain cadmium concentration. Use of potassium tow time more than soil test recommendation was the highest decrease in cadmium concentration by 34 percent. Use of Zn in soil combined with foliar application was the highest effects on seed cadmium decrease by 17. 8 percent in compare to other method. The concentration of cadmium in seed was affected by Potassium and Zinc interaction and decrease significantly. Use of potassium tow time more than soil test recommendation and Use of Zn in soil combined with foliar application decreased seed cadmium concentration by 48. 6 percent significantly. Data also showed that there were a significant correlations between seed potassium and seed zinc concentration and the amount of seed grain cadmium with the quadratic equation، so with increasing concentrations of potassium or zinc، cadmium concentrations of grain declined. On the whole، to reach maximum yield with minimum grain cadmium concentration، Use of potassium tow time more than soil test recommendation and use of Zn in soil combined with foliar application، eventually in lands the same place of research experiment، was recommended.