| In recent years,cadmium（Cd）pollution in farmland soil and its harm have attracted widespread attention from society.The problem of excessive Cd content in rice caused by soil Cd pollution has become a huge threat to food security.In order to achieve the safe utilization of polluted farmland through"production,treatment,and remediation",single remediation technologies such as soil passivation and leaf resistance control have been widely applied.However,the complexity of the regional soil environment and the differences in pollution levels have led to poor stability and universality of a single remediation technology,thereby affecting the promotion and application of a single remediation technology.To achieve stable Cd reduction in rice and improve its universality,a reasonable combination of individual remediation techniques can be considered.Taking typical Cd contaminated farmland in the main grain production area of Chengdu Plain as the object,this study aimed to explore the impact of single remediation technology and combined measures on the Cd content and yield of brown rice of different rice varieties,and further screened out the technical model applicable to the treatment of Cd contaminated soil in this area through the field application effect of three types of measures,namely,in-situ passivation,foliar resistance control,in-situ passivation and foliar resistance control,In order to provide technical support for the safe production of rice in polluted farmland in this region,and also provide ideas and references for the management of Cd contaminated soil and crop safety production in other regions.The main research findings are as follows:（1）The effects of different passivating agents on the Cd content,soil p H,and effective Cd content of brown rice vary greatly.Among the 13 passivating agents tested,10 significantly reduced the Cd content of brown rice,with a Cd reduction rate of16.79%～44.67%;Six types significantly increased soil p H by 0.43 to 0.79 units;Five types significantly reduced the effective Cd content in soil,with a decrease range of28.96%to 36.94%.The comprehensive results indicate that YH passivation agent,IMP soil conditioner,and root hope conditioner exhibit good soil passivation and Cd reduction effects on brown rice,and have no significant impact on rice yield.The Cd content of brown rice shows significant differences between years.The superior passivation agents have not been able to continuously achieve safe production of rice,and there are significant differences in the response of different rice varieties to the same passivation agent’s Cd reduction effect.However,YH passivation agent shows stable and good Cd reduction effect in brown rice between years and varieties.The average Cd reduction rates of brown rice in 2021 and 2022 were 71.13%and 42.35%,respectively.YH passivator significantly increased soil p H,reducing the exchangeable Cd ratio by 6.24%,and increasing the bound and residual Cd ratios of iron and manganese oxides by 2.75%and 2.80%,respectively,resulting in a significant decrease of 53.41%in soil effective Cd content.（2）Different leaf surface inhibitors have a significant impact on the Cd content and rice yield of brown rice.The 10 leaf surface inhibitors tested did not significantly reduce the Cd content of brown rice,but 7 of them still showed certain Cd reducing effects,with Cd reducing rates ranging from 11.19%to 43.05%;Nine types significantly increased rice yield,with an increase rate of 15.94%to 29.82%.The comprehensive results indicate that Tianjie Zinc,Tianjie Iron,and enzymatic elemental nano selenium exhibit good effects in reducing Cd and stabilizing production.The type and dosage of leaf surface inhibitors will have an impact on the Cd content of brown rice in different rice varieties.In the experiment of leaf surface inhibitor dosage,with the increase of Tianjie iron dosage,there was no significant change in Cd content in brown rice of the two rice varieties;The low dosage（225 g·hm2）and high dosage（900 g·hm2）of Tianjie Zinc significantly reduced the Cd content of Dexiang 4103brown rice,with Cd reduction rates of 34.57%and 29.41%;With the increase of the amount of enzyme catalyzed elemental nano selenium,the Cd content in brown rice of both varieties showed a gradually decreasing trend.Under high dosage（7500 ml·hm-2）,the Cd content in Dexiang 4103 brown rice was significantly reduced,with a Cd reduction rate of 25.90%.（3）The combination treatment of passivation agents and low dosage leaf surface inhibitors has a significant difference in the Cd content of brown rice among different rice varieties.Among the 9 combination treatments,8 significantly reduced the Cd content of Zhongyou 177 brown rice,while only 2 significantly reduced the Cd content of Dexiang 4103 brown rice.Compared with a single passivation treatment,the change in Cd reduction rate of brown rice under the combination treatment was not significant.The combination treatment of YH passivation agent and medium dose(450 g·hm-2)Tianjie iron increased the Cd reduction rate of Dexiang 4103 brown rice from 48.61%to 78.95%,and the Cd content of brown rice met the standard set by the International Codex Alimentarius Commission(0.4 mg·kg-1).At the same time,it significantly reduced the Cd content of straw and the transport coefficient from straw to brown rice;The combination treatment of YH passivation agent and high-dose(900 g·hm-2)Tianjie zinc increased the Cd reduction rate of Zhongyou 177 brown rice from 36.08%to73.01%,while significantly reducing the transport coefficient from straw to brown rice.Based on the comprehensive effects of in situ passivation,leaf resistance control,and the combination of in situ passivation and leaf resistance control on the Cd content of brown rice,two technical modes were selected,namely Dexiang 4103+YH passivation agent(4500 kg·hm-2)+Tianjie iron(450 g·hm-2)and Zhongyou 177+YH passivation agent(4500 kg·hm-2)+Tianjie zinc(900 g·hm-2),with better Cd reduction effects than single YH passivation agent treatment. |
PDF Full Text Request