| In order to solve the key technical problems of non-harmful and efficient straw returning to the field under the condition of annual balanced production of rice-wheat rotation,this study proposed a scheme of straw deep rotary tillage and mixed returning to the field based on biaxial cutting principle,aiming at the characteristics of heavy soil texture and large amount of straw returning to the field in rice-wheat rotation area of our province.The purpose of this study was to establish a soil-straw discrete element simulation model suitable for rice and wheat rotation area in Jiangsu province.The process of soil-straw deep tillage was analyzed by discrete element simulation test,and the optimal combination of key parameters was obtained by response surface analysis method to achieve the tillage effect of low power consumption,large tillage depth and high straw cover rate,and the working performance of the prototype was verified by field experiments.The main research contents are as follows:(1)Overall design of biaxial rotary tillage stubble eliminating machine.Based on the principle of biaxial stratified cutting,a biaxial rotary tillage stubble eliminating machine is designed.The front and rear tool axes of the unit were dislocated up and down,and the rear rotary tillage tool set was further plowed 10 cm deep on the basis of the front rotary tillage tool set.In addition,by tillage twice in the same plot,the mixture of straw and soil is realized,so as to solve the problem that the proportion of straw in the traditional tillage soil is too high,which affects the emergence and growth of the next crop wheat.(2)Construction of soil-straw-rotary tillage tool composite model.Based on the research on the physical and mechanical parameters of soil,rice straw and rice stubble in Jiangsu rice-wheat rotation area,the layered discrete element modeling of soil,rice straw and rice stubble was carried out by using EDEM simulation software,and then coupled with two-axis rotary cultivator,the soil-straw-rotary tiller composite model was established.The simulation environment was provided for the subsequent study of soil-straw deep tillage mixing process under biaxial cutting principle.(3)Deep rotary tillage and mixing process for soil-straw and tool optimization.The vertical height of the rear tool shaft relative to the front tool shaft,the rotational speed of the tool shaft and the forward speed of the unit were taken as three factors affecting the working quality.Through the single factor test method,it was found that the key parameters had significant effects on the straw cover rate and power dissipation.Response surface analysis was used to carry out three-factor and three-level orthogonal experiment,and the optimal parameter combination was obtained as follows:Ln=-73.3 mm,w=273.6 r/min,v=0.6 m/s;Under the optimal parameter combination,the tillage performance is as follows:total power dissipation 29.66 kW,straw cover rate 94.6%.(4)Prototype trial production and field test.Complete the trial production of the subject prototype,carry out the grass and soil mixing test,and the grass burial effect is good.Agronomic experiments were carried out in wheat tillage and sowing season to compare the effects of traditional uniaxial rotary tillage(TT),uniaxial rotary tillage twice(ST)and biaxial rotary tillage(DT)on straw returning quality and wheat emergence.The results showed that DT treatment has a good loosening effect on≥20 cm soil layer,soil surface flatness was 2.80 cm,the straw cover rate was 92.6%,the tillage depth stability was 95.3%,and the field emergence rate was 90.5%. |
