| The quality of Panax notoginseng seedlings directly determines the germination and growth of seeds.The effect of soil covering and suppression will directly affect the growth environment of seeds and seedlings,thus affecting the emergence rate and seedling quality.The agronomic requirements of Panax notoginseng planting are special.The spacing of seeding rows is 5 cm,and the depth of seeding is 1cm,which belongs to ultra-precision seeding.However,the current planting mode is still dominated by artificial planting.The planting cost of Panax notoginseng seedlings is high,and there are human errors in the process of pressing holes,covering soil and compaction during artificial seeding,which makes the final row spacing and covering soil thickness uneven,affecting the cultivation of high-quality seedlings.In the early stage,the research team has carried out research on the smooth roller and the sharp-angle soil covering roller for the soil covering and compaction of Panax notoginseng seedlings,but there are problems such as uneven soil covering and compaction,backwater and clay.Therefore,this paper designs a convex ring type soil covering and pressing device for Panax notoginseng seedling cultivation and seeding.During the operation,the soil covering operation is completed through the extrusion of the convex ring on the soil,and the pressing operation is completed under the joint action of the surface of the soil covering and pressing wheel.The specific research contents are as follows:1.Calibration test of soil simulation parameters.The physical intrinsic parameters of soil particles suitable for Panax notoginseng seedlings were measured,and the soil particle size distribution,soil particle density and physical accumulation angle were obtained;The range of soil contact parameters,the surface energy of soil JKR,the static friction coefficient,dynamic friction coefficient and recovery coefficient between soil and soil,between soil and materials of soil-contact parts,and between seeds and soil were measured through tests;The test parameters were optimized.The static friction coefficient,dynamic friction coefficient and JKR surface energy between soil and soil had a significant impact on the soil accumulation angle through the Placket-Burman test.The best parameter combination of significant factors,static friction coefficient,dynamic friction coefficient and JKR surface energy,was obtained through the orthogonal combination test.2.Theoretical analysis of the process of earth covering compaction and structural design of convex ring earth covering compaction wheel.The structure of a convex ring type earth covering roller is designed,and the overall structure and working principle of the earth covering roller are described;By analyzing the movement of soil particles in the process of covering compaction,the sectional area after covering compaction and the compaction strength,the relationship model between the radius of the covering compaction wheel,the radius of the convex ring and the height of the convex ring is obtained when the requirements of covering compaction are met,which provides a theoretical basis for the subsequent parameter design;On the basis of theoretical analysis,the diameter of the earth covering roller,the height of the convex ring,the maximum radius of the convex ring and the distance between the convex rings are designed,the width of the earth covering roller is determined,the maximum load required to achieve the compactness required by agronomy is determined according to the theoretical model of the compaction,and the compression spring of the profiling adjustment device is selected according to the maximum rigidity of the spring.3.Simulation test of the structural parameters of the earth covering roller.The disturbance of soil particle velocity and seed at different height and radius of the convex ring in the process of covering soil compaction is simulated and analyzed,and the range of the height and radius of the convex ring is determined by the simulation results;Taking the height and radius of the convex ring as the factors,and the thickness of the soil cover,the grain spacing offset and the row spacing offset as the test indicators,the single-factor test was carried out,further reducing the size range of the height and radius of the convex ring;Through the quadratic regression orthogonal rotation combination test,the best parameter combination with the minimum grain spacing and line spacing offset is determined,and the height and radius of the convex ring are determined after rounding,and the verification test is basically consistent with the predicted value.4.Soil tank test of soil covering and compaction device.Process and trial-produce the designed earth covering and pressing device;Taking the advance speed of the seeder as the test factor and the grain spacing,row spacing,covering thickness,consistency of covering thickness and soil compactness as the test indexes,the soil trough test was carried out.The test results showed that when the speed of the seeder was 6～8 m/min,the test indexes met the agronomic requirements of Panax notoginseng seeding and seedling cultivation. |
