| The wide application of pesticides has become an important means of pest and disease control in agricultural production.However,traditional pesticides have problems such as easy loss of active ingredients,low utilization rate of target sites,high application rate,easy to increase resistance of pests and diseases,and pollution of ecological environment.It is urgent to find a green and reasonable way to reduce pesticide loss and achieve controlled and precise release of active ingredients of pesticides.In recent years,the application of functionalized carrier materials and "gating materials" in the field of controlled and slow release of pesticides to achieve the "intelligent" release of pesticides and efficient targeted fungicidal effect has become one of the strategic guidelines in response to the "reduction of application and increase in efficiency" of pesticides."It has become one of the strategic guidelines for pesticide application reduction and efficiency increase.Maize,rice and wheat are important food crops,and their common diseases have certain requirements for temperature and humidity,and most of them secrete cell wall degrading enzymes before infesting the crop to destroy the plant cell wall for infestation purposes.Therefore,according to the common disease pathogenesis conditions,the targeted construction of pesticide agents with environmental stimulation response is important to promote the controlled release and efficient deposition of pesticides on target,reduce the application and increase the effectiveness,reduce the toxicity of pesticides to non-target organisms and alleviate environmental pollution.Based on this,this study used corn straw,an agricultural waste,as a carbon source to prepare biochar kernels with high loading of carbendazim through phosphoric acid modification coupled with high-temperature pyrolysis;based on the disease pathogenesis characteristics,cellulose-based organic matter was screened and optimized as a response shell to prepare pesticide agents with multiple environmental stimulation responses of cellulase,temperature and p H.The structural properties of the modified charcoal nuclei and CHBC were investigated by combining with characterization techniques.The results are specified as follows:(1)Preparation study of environmentally responsive pesticide formulations: under the preparation conditions of 20% phosphoric acid and 30 min of pyrolysis at 900 ℃,the best effect of phosphoric acid-modified corn straw biochar was achieved by loading carbendazim,and its maximum loading was up to 443.61 mg/g,which was much higher than the high value reported in the current literature;through the screening and optimization of different organic matter shells,25% carboxymethyl cellulose was used as the responsive shell The best performance of CHBC slow-release carbendazim was achieved through the screening and optimization of different organic shells.(2)Environmental stimulation response performance(controlled release performance)study: CHBC has good response performance to environmental temperature,p H and cellulase.When p H < 7 or > 9,the release rate of carbendazim increased significantly,this characteristic,to a certain extent,can reduce the rapid loss of pesticides in the natural environment and play a certain controlled release effect with the change of p H;under the stimulation of cellulase,the release rate of CHBC to carbendazim increased 2.6 times than that under the environment without cellulase.(3)The slow release performance under no environmental stimulation was studied:compared with the non-CMC-embedded material HBC,the release rate of CHBC to carbendazim was significantly lower than that of HBC at 3 h.The release rate of CHBC to carbendazim at 48 h was lower than that of HBC at 3 h.The release rate of CHBC to carbendazim was significantly lower than that of HBC at 3 h.The kinetic fit analysis showed that the release of HBC to carbendazim was by irregular diffusion-based release mechanism,while the release of CHBC to carbendazim was in accordance with both Peppas model and Higuchi equation,which is a slow release process controlled by swelling.(4)Structural characterization study: The phosphoric acid-modified corn straw biochar(HB)has a well-developed micro-mesoporous structure and graphene structure with large specific surface area and pore capacity;meanwhile,XPS characterization confirmed the presence of abundant oxygen-containing functional groups in the HB structure,which are bound to carbendazim through ionic and chemical bonds;all the above characteristics provide rich binding sites for the loading of carbendazim in the biochar structure.(5)Bioactivity study: CHBC has a significant inhibition effect on spore germination of Fusarium graminearum and Fusarium verticillioides,with the highest inhibition rate of 88%and 85.3% at 24 h,which is 15% and 53.5% higher than that of the commercially available carbendazim,respectively.In the leaf method,CHBC inhibited the mycelial growth of Fusarium graminearum and Fusarium verticillioides up to 18.92% and 37.14%,which were9.01% and 14.28% higher than those of commercially available carbendazim.In summary,CHBC has good slow-release performance for the release of carbendazim,and has certain stimulation response to cellulase,temperature and p H,which can realize the controlled slow-release of the drug through the change of environmental conditions;the release of the drug under the stimulation response of the growth environment of the disease fungus has a significant inhibition effect on the spore germination of Fusarium graminearum and Fusarium verticillioides,and also has a certain retardation effect on the mycelial growth.The effect was also delayed.The environmentally responsive pesticide agents constructed in this study have a positive role in improving the utilization rate of pesticides,ensuring the green and safe production of crops,and promoting the green and sustainable development of ecological agriculture. |
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