| Soil acidification is one of important aspects of soil degradation, which can activate heavy metal elements in soil and increase the harm for crops. In recent years, acidification of paddy field of south China become more and more serious, which is a threat to safe production of rice. Therefore, aimed at the acidification of paddy soil of south China, simulated and field experiments were conducted to study the effects of different soil pH on availability of cadmium in paddy soil, and accumulation and distribution of cadmium in late rice. The main results were as follows:1. Acidification could enhance cadmium availability in paddy soil when pH value was less than 6.5, and available Cd content was increased significantly with the decrement of pH value. Under the same pH, soil available Cd content was increased with the increment of Cd concentration.2. The results of simulated experiment indicated that combination of Cd and acidification seriously prevented growth of rice seedlings and plants, and leaded to death and runt seedlings. The results of field experiment showed that soil acidification inhibited growth of rice plants, and deduced the decrease in biomass and yield. Under normal pH condition, the average yield per hill of Tianyouhuazhan, Xing No.2 and Xiangwanxian No.13 under 3 Cd levels was higher than that under acidified condition by 24.27%,38.51% and 11.89%, respectively. Under the same pH, low Cd concentration gently stimulated growth of rice. Among 3 Cd levels, dry matter weight of 3 varieties in Cd2 treatment was higher at all stages under normal pH.3. Acidification promoted absorption of Cd by rice. Compared with normal pH, Cd content and accumulation were increased significantly under acidification conditions, and the difference was more obvious with the increment of Cd concentration, in which the average increasing extents of Cd content in rice at booting stage under 3 soil Cd levels were 1.148mg/kg,7.364mg/kg and 9.107mg/kg. Correlation analysis showed Cd content in plant was closely related to content of total and available Cd in paddy soil, while related degree was higher between Cd content in plant and available Cd content in paddy soil. Under the same pH, Cd content and accumulation were increased with the increment of Cd concentration in soil.4. Cd was unevenly distributed in plant. Compared with Cd content in leaf and spike, Cd content in root and stem was higher. Among different parts of spike, Cd content in branch was highest, and it was lowest in grain. There existed significantly positive correlation between Cd accumulation in whole plant and Cd content in all organs, the correlation coefficient between Cd accumulation in whole plant and Cd content in stem was 0.954, and it was 0.909** between Cd accumulation in whole plant and Cd content in root.5. Cd accumulation mainly occurred before fully heading stage. From booting to maturity stage, Cd accumulation in leaf and stem showed increasing trend, while changing tendency of Cd accumulation in root was different between two pH conditions. Cd accumulation in root reached to highest at middle filling stage under normal pH condition, while it reached to highest under acidified condition. Compared with middle filling stage, Cd accumulation in spike at maturity stage was higher.6. Cd content and accumulation were different among different varieties. Among three varieties, Cd content in vegetative organ and Cd accumulation in leaf and stem of Xing No.2 was highest and Cd accumulation in root of Xiangwanxian No.13 was higher. As for Cd content and accumulation in spike and brown rice, there showed the trend of Tianyouhuazhan> Xing No.2> Xiangwanxian No.13. |
PDF Full Text Request