Evaluation of Interaction and Residual Effect of Zinc and Cadmium on Growth and Chemical Composition of Rice and Wheat(Rice- wheat rotation) in a Calcareous Soil of Fars Province.

wheat and rice crops are two major crops in Fars province. In paddy field of this province, wheat is cultivated after rice. In water logged condition , the availability of cadmium and zinc change therefore studying the direct and residual effect of them in the first cultivation and particularly in the second one are very important. In order to investigate the direct , residual and interaction effects of these two element in rice– wheat rotation an experiment was carried out. In this research the effect of each element and their interaction effect on yield and chemical coposition, of rice and wheat rotation has during 2 consecutive years investigated. The treatments were combination of 3 zinc levels(0, 15 and 25 kg znso4.H2o per hectare) and 4 cadmium levels( 0, 25, 50 and 100 mg cd per kg soil from cadmium chloride source ) conducted as a factorial experiment was designed as RCBD with 3 replication during 2 years. The experiment data were analyzed by MSTATC software for AVOVA. The results showed that application of Cd and Zn fertilizer and its residual effect on yield(Dry Matter) of rice an wheat is not significant, and on chemical composition of rice and wheat is significant. The results of chemical analysis of rice and wheat showed that the Zn application and its residual effect has a significant effect (p.0 5) on Cd, Zn and Fe concenteration in rice and wheat. In adition to Zn application has a significant effect (p.001) on Mn in rice and Fe, Zn and Cd in wheat.By increasing of Zn level Zn concenteration in rice increased 11.8 percentage and Cd, Mn and Fe concenteration decreased: 28.8, 10.6 and 1.6 percentage respectively. The residual effect of zinc on chemical composition of wheat showed that by increasing the level of zinc application, Zn and Fe concentration of wheat increased 73 and 16 percentage, but Mn and Cd content of wheat decreased %19 and %7.8 respectivly. Also the effect of Cd application on Mn, Cd in two years and Cu, Zn and Fe concentration at second years of rice was statistically significant. Although the residual effects of Cd on Zn(first year) , Mn, Fe and Cd concentration of wheat are statistically significant in two years. Comparing of means showed that; by increasing of Cd levels, concentration of Cd in rice %57 and in wheat%463 increased, and Zn,Fe and Mn concenteration %11, %17.5 , %20.6 in rice and %33, %5 and %31.6 in wheat decreased respectively. Interaction of Cd and Zn effects on Zn, Cd, Mn and Fe concentration in rice and wheat were significant. Key word: Cadmium and residual effects, Rice Wheat, Zinc sulfate