Sprinkler irrigation is effective in reducing cadmium concentration in rice (Oryza sativa L.) grain: A new twist on an old tale?

Literature reports that the adoption of intermittent irrigation techniques instead of continuous flooding irrigation (CF) dramatically increases cadmium content in rice grain. Since rice is the principal human intake source of cadmium, we have felt appropriate to verify the general veracity of this statement. Hence, results relative to the cultivation, in the same experimental site for two consecutive years, of 26 rice genotypes using three different irrigation techniques – namely, CF, sprinkler (SP) and saturation (SA) are reported in this work. As compared to CF, using SP reduced the average concentration of cadmium in rice by between 13% and 28%, whereas irrigating by SA caused an extraordinary increase of cadmium between 760% and 1000%. Indeed, the analysis of data from our experiment and from the literature revealed that the high amounts of cadmium often observed in rice kernels can mostly be explained by the use of SA-like irrigation methods. In light of the evident sensitivity of the bioaccumulation process of cadmium in rice to the adopted irrigation methods, we carefully describe all procedures employed for our study. Finally, a tentative explanation for the opposite effects of SP and SA irrigation methods on the bioaccumulation of cadmium in rice is proposed.