| Rice is an important food crop in my country.It has a strong ability to accumulate Cd and Pb.Cd and Pb in the soil can be absorbed and accumulated by rice,which endanger human health through the food chain.In recent years,the absorption,transport and accumulation of heavy metals in rice have received extensive attention.The absorption of heavy metals by rice largely depends on the availability of heavy metals in the soil and the process of migration and transportation in plants.The absorption and transportation of heavy metals in different growth stages of rice are significantly different.The research group has studied the difference in Cd absorption and accumulation of rice in different growth stages,and found that the filling period and maturity period are the key growth periods for Cd absorption and accumulation in rice.In this paper,through the rice hydroponic experiment,pot experiment and field experiment,the key growth period of rice absorption and accumulation of Pb was analyzed and proved,and the key growth period based on rice Cd and Pb absorption was combined with soil amendment application measures and Zn fertilizer measures at the same time.Reduce the absorption and accumulation of Cd and Pb by rice.The main findings are as follows:(1)Under the experiment of adding exogenous Pb with 0.50 mg·L-1 concentration in different growth periods of rice,the Pb stress treatment of single growth period did not have a significant effect on the rice plant height and tiller number,and it had a certain inhibitory effect on the biomass.The Pb content of brown rice under different growth stages varies from 0.1 to 1.2 mg·kg-1,and the sequence is Pb stress at dough stage<maturing stage<filling stage<tillering stage<jointing stage<booting stage.(2)The relative contribution rates of Pb accumulation in the aboveground parts of rice plants and brown rice are tillering stage,jointing stage,booting stage>filling stage,douph stage,and maturing stage,in which booting stage is the key growth period for Pb accumulation in brown rice,and the relative contribution rate is 43.3%.(3)The results of pot experiments show that the application of 2 and 4 g·kg-1 combination improvers(calcium carbonate,sepiolite and calcium magnesium phosphate fertilizer,LSP)of the combination improver during the key growth period of rice has no effect on the growth of rice.Inhibition;the change trend of soil exchanged Cd and Pb content is the same.Applying 4 g·kg-1 LSP before transplanting has the largest decrease,with a decrease of 60.9%and 62.1%respectively;applying LSP exchanged Cd before booting stage and before filling stage,Pb content has decreased,but the decline is small.(4)The total Cd and Pb contents of the tested soil were 3.49 and 312.74 mg·kg-1,respectively.The application of 4 g·kg-1 LSP at the booting stage can simultaneously reduce the Cd and Pb content of brown rice to 0.15 and 0.18 mg·kg-1 respectively.For Cd,applying 4 g·kg-1 LSP treatment before transplanting had the best effect on reducing the Cd content of brown rice,and the reduction rate was 55.2%,respectively.The Cd content of brown rice was reduced to 0.13 mg·kg-1.For Pb,the 4 g·kg-1 LSP treatment before the filling stage had the best effect in reducing Pb content,with a decrease of 78.9%,and the Pb content of brown rice was 0.16 mg·kg-1.The contents of Cd and Pb in the above-mentioned treated brown rice are lower than the limit(0.20 mg·kg-1)in the national food contaminant limit standard(GB 2762-2017).(5)Field test results show that applying 20 mg·L-1 of Zn fertilizer in the rice booting stage and grain filling stage has the best effect in reducing soil pore water Cd,and each treatment cannot significantly reduce the pore water Pb content at the same time.(6)The total Cd and Pb content of the soil were 3.19 and 89.79 mg·kg-1,respectively.The application of Zn fertilizer during the key growth period could reduce the Cd and Pb content in each part of the rice.The application of 20 mg·L-1 Zn fertilizer from the booting stage to the grain filling stage reduced the Cd and Pb content.The content of Cd and Pb in brown rice had the best effect.The content was 0.12 and 0.005 mg·kg-1 respectively,with a decrease of 87.4%and 16.7%respectively,which reached the national food contaminant limit standard.In this experiment,the Zn content in the treated brown rice was from 16.06 to 19.74 mg·kg-1,and the Zn element was not in the national food contaminant limit standard.It is recommended to use irrigation technology measures of 20 mg·L-1 Zn fertilizer in both the booting stage and the filling stage of rice to reduce the accumulation of Cd and Pb in brown rice and realize the safe use of Cd and Pb polluted rice fields. |
PDF Full Text Request