Development And Test Of Digging And Covering Equipments Of Plug Seedling

Because of its good economic benefits and high quality,the vegetable seedling with large-scale,automated and mechanized production becomes more and more popular.With the advantages of time-saving,good seedling quality and high survival rate,the plug seedling has become the preferred choice for seedling enterprises.The production line of plug seedling consists of six parts which includes soil-filling,soil-digging,seeding,and soil-covering.The digging and covering parts are related to the sowing depth and covering thickness,which directly affect the germination quality of seeds.In addition,the center performance and pore-forming quality of digging part have an influence on the operation of seedling transplanting.Therefore,the research on the digging and covering to ensure the seedling effect,has important significance in ensuring the seedling quality,improving the transplanting quality and production efficiency.In this paper,the digging and covering devices were optimal designed based on the analysis of research status and the performance of the prototypes was tested.In addition,a seedling experiment on the tomato seeds was done to investigate the effects of different digging and covering methods on growth quality.The main research contents includes:(1)Design and experiment of synchronous digging device.Based on the theoretical analysis of the unpowered rotating device for digging,the methods of sectional synchronous digging and linear reciprocating cleaning were put forward,and the corresponding digging device had been developed by 3D simulation,in which the speed of the tray is equal to the roller to ensure synchronous digging by the design of gear transmission and chain drive.The results of center performance experiment showed that the effect of the digging depth and the digging speed on the center performance was small,which could meet the requirements of seedling transplanting.The major and minor order of the effects on pore-forming quality of every factor was the substrate water content,digging depth,and digging speed.The effect of substrate water content on the pore-forming quality was very significant,while the digging speed had little influence.The optimal combination of the digging device was using the middle digging depth of 15 mm,substrate water content of 67%,and digging speed of 500 disc/h at the given level.The pass rate was 98.41%.(2)Design and experiment of soil-covering device.Because the existing devices of the covering part aren't suitable for the low-quality substrate,a covering device equipped with the angle steel-chain was put forward.The angle steels which were welded to the chain scraped the substrate in the hopper to the trays automatically.The results of the covering uniformity test showed that the device was more suitable for the low-quality substrate,and no blocking phenomenon occurred.Besides that,when the covering thickness was more than 9.59 mm,the soil covering surface was smooth without the leveling mechanism,which met the requirement of the plug seedling.(3)Performance test of auto-washing device for seedling tray.As the residual substrate has an influence on the seedling growth,the trays are required to be washed before the seedling test.The trays used at home are so soft that there is no suitable washing parameters for them.To enhance the washing effect and reduce the damage,a washing performance test was conducted by using the self-developed auto-washing device,which came to a conclusion that the major and minor order of the effects on washing effect of every factor was the washing times,water pressure,and tray speed.Besides,at a given level,the optimal combination of the washing device was using the 6 washing times,washing speed of 900 disc/h and washing pressure of 5 bar.The clean rate was 98.56%.(4)Research on effects of different digging methods and covering thickness on growth quality.Based on the preliminary designs and tests,a split plot seedling experiment on the tomato seeds with two digging methods(synchronous and unpowered)and four covering thickness(20,15,10,5mm)was designed.The results showed that the covering thickness had a very significant impact on the seedling growth,and the optimum thickness was 10 mm.Higher and lower covering thickness would lead to seedling index decreased,as well as morphological indexes such as stem diameter and matter accumulation reduced.Beyond that,the germination rate and seedling emergence rate were significantly increased at the treatment of unpowered digging,and the stem diameter,matter accumulation and seedling index increased as well as the stem height reduced.Therefore,the preliminary design of the devices were feasible,and the measures to improve the seedling growth of synchronous digging with 10 mm covering thickness were recommended.This study can provide theoretical references for the design of the washing,digging and covering device,and be helpful to improve the growth quality of plug seedling.