Migration Characteristics And Influencing Factors Of Cadmium In Giant Rice Under Rice Fish Ecological Planting And Breeding Model

Cadmium,a heavy metal,has great toxicity and harm to organisms and is classified as the first category of human carcinogens.In China,the problem of cadmium pollution in rice fields is widespread and threatens food security all the time.Rice fish farming can not only improve economic benefits,but also have good ecological effects,such as reducing the use of pesticides and chemical fertilizers and reducing the migration of heavy metals in rice fields.Selecting appropriate rice varieties to carry out rice fish planting and breeding can effectively ensure the yield and quality of rice.Giant rice is very suitable for rice fish ecological planting and breeding because of its excellent characteristics such as large biomass,high plant,high yield and flood resistance.In order to explore the migration characteristics and influencing factors of cadmium in giant rice under the ecological planting and breeding mode of rice fish,this study compared the cadmium enrichment characteristics of Juxiang 2,Nongxiang 32 and Jingliangyou 510 in the rice fish planting and breeding mode with high cadmium background in soil(HRF)and rice fish with low cadmium background in soil(LRF),And the differences of cadmium enrichment characteristics of three rice varieties between rice fish planting and breeding model with low cadmium background and rice monoculture with low cadmium in soil(LM),and the causes of these differences were discussed from four aspects: cadmium form in rhizosphere soil,Chemical properties of Rhizosphere Soil,enzyme activity in rhizosphere soil and biological properties of rice.The main results of this study are as follows:(1)In HRF,the content of cadmium in the root of Juxiang 2 was 8.39 mg/kg,which was significantly higher than that of Nongxiang 32(3.66 mg/kg)and Jingliangyou 510(4.5 mg/kg);The cadmium content in stems and leaves was 1.13mg/kg,which was significantly lower than that of Jingliangyou 510(1.56 mg/kg);The content of cadmium in grains was 0.1 mg/kg,which was significantly lower than that of Nongxiang 32(0.19 mg/kg)and Jingliangyou 510(0.22 mg/kg);The root stem leaf cadmium transport coefficient(TF stem & leaf / root)was significantly lower than that of Nongxiang 32 and Jingliangyou 510.Compared with HRF,there was no significant difference in root cadmium content,stem and leaf cadmium content,grain cadmium content,TF grain / stem & leaf with Nongxiang 32 and Jingliangyou 510 in LRF.In HRF treatment,the content of cadmium in root and stem and leaf of Juxiang2 was significantly higher than that in LRF treatment,while TF stem & leaf / root and TF grain / stem & leaf were significantly lower than that in LRF treatment.There was no significant difference in grain cadmium content between HRF and LRF treatment.In LM treatment,the cadmium content of Juxiang 2 root was 0.75 mg / kg,which was significantly higher than that of nongxiang 32;The content of cadmium in stems and leaves was 0.17 mg / kg,which was significantly lower than that of jingliangyou 510;There was no significant difference in grain cadmium content between nongxiang 32 and jingliangyou 510;TF stem & leaf / root was significantly lower than that of nongxiang 32 and jingliangyou 510,while TF grain / stem & leaf had no significant difference with the other two rice varieties.Under the background of low cadmium in soil(0.29 mg/kg),there was no significant difference in cadmium content and cadmium transport coefficient between LRF and LM treatment.(2)The results of correlation analysis showed that the content of available cadmium in soil was an important factor affecting the migration of cadmium from soil to rice;Rice biomass and plant height are important factors affecting the migration of cadmium from plants to grains.In HRF,LRF and LM treatments,the contents of weak acid extracted cadmium in rhizosphere soil of Juxiang 2 were 0.73 mg/kg,0.113mg/kg and 0.15 mg/kg respectively,which were significantly higher than those of nongxiang 32 and jingliangyou 510.The higher the content of soil cadmium,the higher the content of weak acid extracted cadmium in rice rhizosphere soil,while the content of weak acid extracted cadmium in rice monoculture model is higher than that in rice fish model.The content of weak acid extracted cadmium in soil was significantly negatively correlated with soil p H and organic matter(SOM),and positively correlated with the activities of acid phosphatase(ACP),invertase(INV)and N-acetylglucosaminidase(NAG)in rhizosphere soil.In HRF,LRF and LM treatments,the biomass and plant height of Juxiang 2 were significantly higher than those of nongxiang 32 and jingliangyou 510.There was a significant positive correlation between rice biomass and BCF root,and a significant negative correlation between plant height and TF stem & leaf / root.(3)The yield of Juxiang 2 in each treatment was significantly higher than that of the other two kinds of rice.In HRF treatment,the theoretical yield of Juxiang 2 was57% higher than that of Nongxiang 32 and 58% higher than that of Jingliangyou 510;In LRF treatment,the theoretical yield of Juxiang 2 was 60% higher than that of Nongxiang 32 and 55% higher than that of Jingliangyou 510;In LM treatment,the theoretical yield of Juxiang 2 was 52% higher than that of Nongxiang 32 and 34%higher than that of Jingliangyou 510.In all treatments,the economic benefits of Juxiang 2 were higher than those of nongxiang 32 and jingliangyou 510.In conclusion,compared with nongxiang 32 and jingliangyou 510,Juxiang 2 has a lower risk of cadmium pollution in rice,and its yield and economic benefits are higher.The giant rice fish compound planting and breeding model can be used for the safe production of rice in rice fields with moderate and severe cadmium pollution.