Abstract: According to the field experiment next to a lead-zinc mining area in Anhui Province, the available cadmium (Cd) and arsenic (As) in farmland as well as rice yields were evaluated as affected by charcoal and diammonium phosphate (DAP) treatments under conventional irrigation (W1), whole growth period flooding (W2), and wet irrigation (W3). Moreover, the pH values, oxidation-reduction potential (Eh), and Cd and As accumulation in rice tissues were also investigated in this study. The results demonstrate that the application of charcoal and DAP enhanced the pH values in soils under all the three conditions of water management. With the rice growth, the pH value in farmland increased firstly and then decreased to neutral. The Eh values of soils showed a declining tendency with the increase of moisture. The Eh values under the different water management conditions followed the sequence of W1 > W3 > W2. Furthermore, the Eh values at W2 condition showed a weak reductive state. At the same water management condition, the available Cd content in soil and Cd content in root, stem leaves and grains decreased as the application amount of charcoal and DAP increased, respectively. In control group, the Cd contents in rice grains under W1, W2, and W3 treatments were (0.23±0.02), (0.19±0.03), and (0.22±0.04) mg·kg^-1, respectively. After the charcoal and DAP application, Cd accumulation in rice grains was lower than 0.2 mg·kg^-1 for all treatments. It was found that the reduction in Cd accumulation had an optimum efficiency in application of 0.44 kg·m^-2 charcoal or 15.00 g·m^-2 DAP under W2 treatment. On the other hand, the available As content increased after the charcoal and DAP application. The available As content in soil showed the lowest concentration range (0.88-1.22 mg·kg^-1) in W2 treatments. In the W2 treatment group, it was observed that the available As content in soil and As accumulation were lower in rice roots, stem leaves and grains. Meanwhile, the inorganic As contents in rice grains were lower than 0.2 mg·kg^-1. Overall, application of charcoal and DAP improved rice growth and increased rice yield. The rice yields were negatively correlated with the available Cd content in soil, but no significant correlation with the available As content was observed. Therefore, the application of 0.44 kg·m^-2 charcoal or 15.00 g·m^-2 DAP coupled with W2 water treatment could be adopted to promote rice yields in the condition of ensuring that As content in rice grains below 0.2 mg·kg^-1, which simultaneously decreased the accumulation of Cd in rice grains.

Key words: rice, Cd, As, water management, charcoal, diammonium phosphate