Evaluating the Various Cropping Systems on Cd Concentrations of Different Growth Stages of Wheat

Soil contamination with heavy metals would accumulate these elements in plant tissues and decrease qualitaty and quantity of agricultural producs and thus endanger human and animal healths. Previous crop residues and rates of fertilizers applications (especially phosphorus fertilizer) are the most important effective factors on accumulation of cadmium in crop tissues. Another influential factor affecting soil shrinkage is crop rotation which induces the solubility of cadmium. This research was aimed to assess the effects of conventional cropping system on cadmium concentrations in wheat at its different growth stages by using a split plot in time experiment based on completely randomized block design with three replications in the 2014-2015 growing season in Shavoor Agricultural Research Station (Khuzestan province). Main plot consisted of cropping system (rice-wheat, fallow-wheat) and sub plot of growth stages at three levels (tillering, flowering and ripening). Different wheat seed cadmium concentrations due to two cropping systems were different significantly at 1% probability level. Cadmium concentration in the seeds at rice-wheat cropping system (0.31 mg.kg-1) was higher than fallow-wheat system (0.27 mg.kg-1) which is higher than World Health Organization standards. Result of analysis of variance showed that the effect of cropping systems and different growth stages of wheat on root and stem cadmium concentrations were significant at 1% probability level. Rice-wheat cropping system resulted in higher cadmium concentration in root (1.09 mg.kg-1) and stem (0.73 mg.kg-1) compared to that of the fallow-wheat cropping system. Accumulation of cadmium in stem or root at different growth stages of wheat were not significant but it was totally additive, because range of variation of cadmium concentration from planting to harvest was low.