Effects of water management on soil heavy metal transport and rice quality safety

Water management in rice planting controls the rice quality safety.An experiment, including water treatments as roots ridging (RR), intermittent flooding (IF), continuous flooding (CF) and conventional planting (CK), was conducted to study the effects of different water management models on the movement and transport of heavy metals Pb, Cd and As in soil, as well as their effects on rice quality safety.The results showed that RR and CF models significantly decreased the contents of heavy metals in soil; while IF and CK models did not change the contents of heavy metals.RR, IF and CK models had little effect on soil As activity, while CF model enhanced As content significantly.Heavy metal Cd was easier to be activated than Pb and As; CF and CK models significantly enhanced Cd activity, while RR and IF models had little effect on Cd activity.The Pb activity was not related to water management models.The RR and IF water models significantly reduced the contents of Pb, Cd and As in rice roots.The contents of heavy metals in rice roots and stems in IF model were with the highest value, while the content of As in RR model was significantly lower than that in other models.The RR and IF models significantly reduced the heavy metals content in brown rice, which was lower than the National Standard for Food Safety Limits of Contaminants in Food (GB 2762-2017), indicating that the quality of brown rice was safe.The RR model was with the superior ability to transport heavy metals in the soil from roots to stems and leaves, and the inferior ability to transport heavy metals from the roots to brown rice.CF and CK models were with higher transport coefficients from root to stem and leaf as well as from stem and leaf to brown rice, indicating a stronger transport ability from roots to brown rice, especially for Cd.The roots ridging and intermittent flooding are recommended to achieve safe planting of rice in moderate and mild heavy metal risk areas under controllable planting environment.