Straw removal to reduce cadmium uptake in rice( Oryza sativa L.) at different growth stages: effect, rice quality and risk assessment

Compared with straw return to the field, whether straw removal was a safer production measure in cadmium (Cd) contaminated paddy fields? In this study, the influence of different amounts of rice straw removal on rice growth, photosynthesis, Cd accumulation and uptake in rice, and soil Cd availability at different growth periods, as well as brown rice safety and quality, were evaluated through a field trial, and all rice straw and roots returned to the paddy were used as controls (CK). The results showed that although straw removal decreased photosynthetic pigment content in rice leaves, which affecting rice growth. The chlorophyll a and chlorophyll b contents in the removal of 100% rice straw and 100% roots treatment declined by 36.72% and 22.74%, respectively, relative to the control at booting stage,and the biomass of brown rice at the maturation stage was also significantly reduced by 22.77%. However, straw removal reduced the bioavailability of Cd in soil and accumulation and uptake of Cd in rice. At the maturation stage, soil available Cd content under the treatment of removal 100% rice straw and roots was significantly reduced by 40.39%, DOC and Cd concentrations in pore water were significantly decreased by 66.54% and 76.44%, and the Cd content of brown rice in all straw removal treatments decreased by 24.79%, indicating that the reduction of complexation of DOC and Cd through straw removal treatments is also one of the important reasons for decreasing of Cd accumulation in rice. The nutritional components (such as essential amino acids) of brown rice were slightly influenced by all the straw removal treatments, the ecological risk of soil Cd was significantly reduced. Therefore, straw removal may be an effective measure for reducing Cd uptake by rice in Cd-contaminated paddies.