The effect of irrigation and zeolite management on the reduction of cadmium accumulation in rice

Cadmium (Cd) is one of the most toxic heavy metals accumulated in the human body and last for a long time, posing a significant risk to human health. This study aimed to investigate the effects of different irrigation and zeolite management on the absorption of Cd in rice shoots. To do so, we conducted a factorial experimental design with three replications during the summer of 2014. Three irrigation managements were used: saturation (I100), controlled water level at 20 cm subsurface (50 % of the root depth saturated - I50), and controlled water level at 36 cm subsurface (10 % of the root depth saturated - I10). Zeolite was applied in three forms: modified zeolite (ZM), natural zeolite (NZ), and no zeolite (Z0). Subsurface irrigation and controlled drainage methods were applied to fix the water level. Zeolite was modified in the solution of CaCl2, and HCl acid. The soil pH was monitored during the cropping season, and Cd concentrations in the shoot were measured at the end of the experiments. Analysis of variance indicated that applying the treatments individually had a significant effect on Cd absorption in the plant (seed, stem, and leaf) and soil (p < 0.01). The Cd concentrations were highest in the I100 (0.1, 1.379 and 0.25 mg.kg-1) and Z0 treatments (0.091, 1.378 and 0.207 mg.kg-1) in soil, stem and seed, respectively. Furthermore, in the I10 and ZM treatments, zeolite adsorbed a high amount of Cd compared with the control (I100 and Z0) so that the soil's available Cd was decreased in these treatments. Furthermore, I10 and I50 decreased the Cd levels by 54.8 % and 43.9 % in the seed; 38.9 % and 20.3 % in the stem and leaf; 49.0 % and 22.8 % in the soil, respectively. The results revealed that applying modified zeolite and natural zeolite reduces the Cd concentrations by 32.8 % and 24.1 % in the seed; 32.3 % and 26.7 % in the stem and leaf; 30.8 % and 16.5 % in the soil, respectively. Overall, it was concluded that the Cd concentration in rice plant could be reduced by using modified zeolite and maintaining appropriate soil's water content.