Effects of chicken manure application on cadmium and arsenic accumulation in rice grains under different water conditions.

Widespread contamination of agricultural soil with Cd and As has resulted in substantial transfer and accumulation of these toxicants in rice grains. In the present study, we investigated the effects of chicken manure application on Cd and As concentrations and As speciation in the rice grains grown under different water conditions by pot experiment. Under aerobic condition, the application of chicken manure increased soil pH and soil Eh during most of the growth period of rice. Consequently, the application of chicken manure has little effect on total Cd, slightly decreased total As and inorganic As of rice grains when applied at rate of 2.0%. Under intermittent irrigation condition, the application of chicken manure increased soil pH and decreased soil Eh during most of the growth period of rice. Thus, chicken manure decreased total Cd, As, and inorganic As of rice grains. Besides, there was increased reduction of Cd and As with increase in the amount of chicken manure applied. Under flooded condition, the application of chicken manure increased soil pH before heading but decreased soil pH after heading. The application of chicken manure dramatically decreased total and inorganic As in rice grains, and slightly decreased Cd of rice grains. There was increased reduction of total As concentration with the increase in the amount of chicken manure applied. Meanwhile, the inorganic As concentration was the lowest when the concentration of chicken manure was 1.0%.