REMEDIATION EFFECTS OF MAIZE-STRAW-DERIVED BIOCHAR ON RICE GROWN IN CADMIUM-CONTAMINATED SOIL IN NORTH CHINA

To assess biochar potential for cadmium (Cd)-contaminated soil, a pot experiment was conducted with samples of typical farmland soil from Shenyang area(North China), which was contaminated with cadmium due to sewage irrigation. Two maize-straw-derived biochar concentrations(11250 and 22500 kg.hm(-2)) were tested. The results showed that the biochar prepared with dry distillation of carbonization technology under oxygen-deficient conditions and low temperature(400-450 degrees C) had appropriate structural features and physical and chemical properties. The use of such biochar reduced the available-Cd ions in the contaminated soil, with a "passivation or inhibitory" effect which displayed a variable time-dependent response. The biochar led to soil pH changes during rice growth(increase followed by a decrease). Furthermore, the biochar significantly improved the soil organic matter and available-nutrients(N, P, K), and indeed a cumulative effect with time was observed. More importantly, the biochar significantly reduced the cadmium content in rice grains by an average of 33.01% compared to the control(CK), the treatment with higher biochar concentration being more effective; this indicates a decreased bio-availability of the cadmium. These results suggest that maize-straw-derived biochar is an effective remediation material for Cd-contaminated soil, which has good application potential for the environment.