| Rape is an important oil crop in China.In 2020,the planting area of rape in China was about 6.583 million Hm~2and the output was 14.049 million tons.The planting area and total output accounted for about one third of the world.The middle and lower reaches of the Yangtze River are winter oil vegetable areas and one of the main rape producing areas in China.The planting area accounted for about 90%of the country.The water and dry rotation planting mode of double cropping or triple cropping of rice and rape was adopted,resulting in prominent stubble contradiction,Mechanized transplanting of rape seedlings is one of the important production ways to alleviate the stubble contradiction.This paper studies the key parts of rape seedling transplanting machine,such as the lack of matrix transplanting and transplanting machine,and puts forward a scheme to improve the compatibility of matrix transplanting and transplanting machine in China,The structure and operation parameters of the counter roll seedling separation device were optimized,the field operation performance of the transplanter before and after the improvement was compared and verified,and the differences between the transplanted plants and the machine sown plants were analyzed.The specific research contents include:(1)The mechanical and biological characteristics of rape seedling matrix were tested and analyzed.Taking the square rape seedling matrix block as the research object,the compression characteristics and drop loss rate mechanical characteristics of rape seedling matrix block at the suitable planting stage were measured.The biological characteristics of rape seedlings such as stem diameter,plant height,root dry matter mass,stem and leaf dry matter mass and root distribution characteristics were analyzed.The orthogonal test was carried out with the ratio of matrix components,matrix compactness and boron and selenium nutrient solution concentration as the experimental factors,The results showed that the effects of matrix component ratio and matrix compaction on the mechanical properties of rape seedling matrix blocks were very significant and significant respectively;Substrate distribution ratio and substrate compactness had a significant effect on seedling index,and the concentration of boron and selenium nutrient solution had a significant effect on it;The proportion of substrate components and the degree of compaction of substrate had a significant effect on the matrix wrapping degree and root robustness,and the concentration of boron and selenium nutrient solution had a significant effect on the matrix wrapping degree and root robustness;The comprehensive scoring method showed that when the matrix component ratio was 1:1:1,the matrix compactness was 1.2 and the concentration of boron selenium nutrient solution was0.30%,the mechanical properties and seedling growth quality of rape matrix block seedlings were better,which met the requirements of rape seedling raising agronomic technology and mechanical transplanting.The study provides a reference for the formulation of mechanized transplanting and seedling raising scheme of rape matrix block seedlings.(2)A two-way progressive seedling feeding device for rape matrix block seedling transplanter was developed.According to the analysis of mechanical properties of rape seedling matrix block,the kinematic and dynamic models of horizontal progressive seedling feeding stage and vertical continuous seedling feeding stage were constructed.The design and parameter analysis of key components such as transverse seedling feeding mechanism and longitudinal seedling feeding mechanism are carried out.It is determined that the height of seedling frame bottom,the height of upper guide rod and longitudinal seedling feeding speed are the main factors affecting the stability of seedling feeding;The single factor test results show that when the height of seedling frame bottom is 5～25mm,the height of upper guide rod is45～55mm and the longitudinal seedling feeding speed is 80～140mm/s,the seedling feeding effect is better;The results of orthogonal combination test showed that when the seedling frame bottom height was 10.7mm,the height of upper guide rod was50.0mm and the longitudinal seedling feeding speed was 140.0mm/s,the seedling feeding effect was better.The synchronization rate and power of seedling feeding were 94.54%and 93.13%respectively.The research provides a reference for the design of seedling feeding device of rape matrix block seedling transplanter.(3)The seedling separation device of rape matrix block seedling transplanter was designed.The key working parts of the seedling separation and extraction device include pneumatic seedling separation mechanism and counter roll seedling extraction mechanism.Combined with the analysis of the mechanical characteristics of rape seedling carrier matrix block,the kinematic models of pneumatic seedling separation stage and counter roll seedling extraction stage in the process of transplanting are constructed.The design and parameter analysis of the key components of the pneumatic seedling separation mechanism and the counter roll seedling taking mechanism are carried out,and the working parameters of the stable operation of the seedling separation and taking device are determined as follows:the angle of the seedling carrier should be 30°～45°,the longitudinal seedling feeding speed range should be 66.67～133.33mm/s,and the linear speed range of the roller should be192.46～294.67mm/s;The performance optimization test of the seedling separation device was carried out.When the single row seedling extraction frequency of the transplanter was 50 plants/min,the orthogonal combination test results showed that when the longitudinal seedling feeding speed was 120.9mm/s,the linear speed of the roller was 238.2mm/s and the angle of the seedling platform was 31.9°,the seedling extraction effect was better,and the synchronization rate and success rate of seedling separation were 93.42%and 94.42%respectively.The research provides a reference for the design of seedling separation device of rape matrix block seedling transplanter.(4)The counter roll seedling separating device of rape matrix block seedling transplanter was optimized and improved.In order to improve the working frequency and seedling dropping stability of rape seedling carrier matrix block separation and picking device,the linkage mechanism of separation and picking device and roller picking mechanism were optimized,the kinematic models of pneumatic seedling stage and roller picking stage in the process of seedling picking and planting were constructed,and the structure and working parameters of stable operation of seedling picking device were determined.The orthogonal combination test of three factors and three levels was carried out based on the influence of seedling carrier angle,roller bottom diameter and roller speed on the success rate and synchronization rate of seedling collection.The results showed that the seedling collection effect was better when the angle of seedling carrier was 30.7°,the diameter of roller bottom was26.4mm and the roller speed was 2.2r/s.The results of bench test with the combination of better parameters:the success rate of seedling collection was 94.62%and the synchronization rate of seedling collection was 95.35%;Three dimensional high-speed photography was used to extract and analyze the change of the bottom angle of rape seedling matrix block in the process of seedling picking.Compared with the theoretical analysis track,the analysis results showed that the average change of the bottom angle of rape seedling matrix block in the actual process of seedling picking was 12.76°,compared with the theoretical analysis value of 17.58°,and the error was 27.42%.The research provides a reference for the optimization and improvement of the seedling separation device of rape matrix block seedling transplanter.(5)The field operation performance of the transplanter before and after optimization and the plant characters at harvest under different planting methods were compared and analyzed.a)The field operation performance test of transplanter was compared and analyzed.Taking the planting success rate and planting synchronization rate as the evaluation index,under the better combination of working parameters,the field experiments of rape matrix seedling transplanter were carried out in October 2020 and November 2021 respectively.The results showed that before and after the optimization of the transplanter,the planting success rate of the transplanter increased from 88.67%to 89.84%,the seedling taking frequency of each row increased from 50plants/min to 60 plants/min,and the seedling taking efficiency increased by 20%;On the premise of increasing the number of working rows from 4 to 6,the planting synchronization rate decreased from 92.71%to 92.01%.During the field test,the main reasons for the failure of transplanting are:the flatness of the seedling bed of the transplanter needs to be improved,there is vibration in the working process of the machines and tools,resulting in the stability of seedling falling needs to be improved,and the phenomenon of soil particles splashing into the seedling feeding synchronous belt and counter roller during the test,resulting in the jamming of seedling feeding and taking.b)In April 2021,the comparative analysis of the characters of field transplanted rape matrix block seedlings and machine sown plants was carried out.The results showed that in the early stage,the nutrition supply of rape matrix block seedlings in the young seedling stage was sufficient,the seedlings grew strong,and the transplanting density of rape was small.In the characters of rape matrix block seedlings in the field,the stem diameter,the effective length of main inflorescence and the number of effective pods of the whole plant were 16.35mm,49.9mm and472.8 respectively,Compared with machine sown rape,it increased by 50.41%,28.31%and 175.31%respectively;Due to the good illumination and ventilation environment in the field during the growth of transplanted rape seedlings,there is no need to strive for illumination time for rape growth for a long time,resulting in 111.85mm,6.3 mm and 51.8 effective pods in the matrix block of transplanted rape,which are 15.7%,86.88%and 15.14%lower than that of machine sown rape;The yield per plant of transplanted rape was 27.17 g/plant,which was 392.21%higher than that of machine sown rape;According to the planting density,it is predicted that the field transplanting yield of rape matrix block seedlings is about 180.95kg/mu,and the predicted yield of machine sown rape is about 165.05kg/mu,with an increase of9.63%. |
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