Experimental study on mechanical and physical properties of pakchoi seeds

In order to obtain the best structural and working parameters of positive and negative air pressure combined seed metering device,the effects of seed variation on seed filling performance and seed feeding accuracy of pneumatic seed metering device were studied.The seed mass,triaxial size,water content,1 000-grain weight,angle of repose and angle of sliding friction of 10different varieties of pakchoi seeds were tested,and the probability distribution characteristics of seed width and sphericity of pakchoi were analyzed.The results showed that the seed width distribution of pakchoi was concentrated in 1.47-1.61 mm,accounting for more than 80% of the total,the average width was 1.53 mm.The sphericity distribution was concentrated in 85%-95%,accounting for more than 85% of the total,the average sphericity was 90.41%.The average value of sliding friction angle on ABS was 13.75°．The length and width of pakchoi seeds were close to each other,and the seed size distribution was concentrated near the average value in all directions.The shape of pakchoi seeds was similar to spherical,and the width of different varieties of pakchoi seeds was different.The pressurebearing load of pakchoi seeds increased with the increase of the displacement of rupture test probe.As the seed breaks,the maximum value of pressure-bearing load was 9.6N,and its final curve changes was unobvious.It provides an important basis for the design of positive and negative air pressure combined seed metering device,ensures the sowing accuracy of precision direct seeding of pakchoi,meets the agronomic requirements of standardized plant spacing and row spacing of pakchoi,and improves the mechanized production degree of pakchoi and the utilization rate of machines and tools.