The determination of parameters is a key issue in discrete element simulation and controls the accuracy and reliability of the simulation results. In this paper, a sandy loam soil with three water contents is studied and soil particles based on the EEPA model are modelled in three shapes (spheres, columns and Triangular pyramid) to accurately represent the actual soil particle. The sensitivity of the input parameters in the EEPA model is investigated by the Plackett–Burman test. The results show that the coefficient of static friction, coefficient of rolling friction and surface energy between soil particles have a highly significant effect on the angle of repose, and the coefficient of restitution has a significant effect on the angle of repose. The sensitivity parameters are calibrated by the central combination test, and the optimal combination of parameters is obtained. The accuracy of the parameters calibrated is validated by comparing the simulation results of the direct shear test with the actual test results. Therefore, the parameters calibrated satisfy both the flow and mechanical properties of the particles.

An appropriate contact mechanics model and parameters are key to achieving accurate results in discrete element analyzis. This is necessary to predict the process of contact collision between the soil and maize seed during deposition. In this paper, the contact process between maize seed and soil is analyzed using the maize seed variety (Liangyu 99) and maize-sowing field soil (with three different moisture contents) as research objects. Based on this, the contact process between maize seeds and soil has been analyzed, on the basis of which a mechanical model suitable for simulating the contact process between maize seeds and soil has been explored, and the selection of parameters between heterogeneous particles (maize seed and soil particles) has been investigated. The results showed that adhesion forces have a significant effect on the collision process between seed and soil particles. While the presence of tangential adhesion force can be replaced by increasing the static and rolling friction coefficients, the normal adhesion force cannot be compensated in this way. The Edinburgh Elasto-Plastic Adhesive (EEPA) model is selected in this paper to describe the contact between seed and soil particles. The significance of the input parameters in the EEPA model is investigated using the Plackett–Burman test. The parameters between soil and seed particles are optimized using the central composite design, and the optimal parameter combinations are obtained. The relative error between the simulation and test result of the slope test for the three soil moisture contents is within 5.4%, validating the accuracy of the calibrated parameters.

The soil properties of seedbed directly affect crop emergence and growth. To find out the optimal soil properties of seedbed for maize (Zea mays L.) seed in Northeast China, the strip till planter was designed. The effects of seed furrow treatments, surface compaction forces, water spraying treatments and their interactions on maize growth were evaluated. The experiments used a randomized complete block design, consisting of 24 treatments, in a 2 × 3 × 4 factorial arrangement. Two seed furrow treatments were: bottom compaction (BC) and no bottom compaction (NBC). Each seed furrow treatment included the combination of surface compaction force (25, 50 and 75 kg) and water spraying treatment (0, 2.8, 5.7 and 8.6 m³ ha⁻¹). We have come to the conclusions that the performance of BC treatment was better than that of NBC treatment, meanwhile the compaction force of 25-50 kg and the spraying water volume of 5.7-8.6 m³ ha⁻¹ were the best choice for maize emergence and growth in Northeast China. This study provides a reference for the establishment of the optimal maize seedbed and the innovation design of maize precision seeder.

In the production process of maize, the uniformity of maize sowing is one of the main factors affecting maize yield. The effect of soil coverage and the compaction process on sowing uniformity, as the final link in determining the seed bed position, needs to be further investigated. In this paper, the parameters between soil particles and boundaries are calibrated using the Plackett–Burman test and the central composite design. Furthermore, based on the DEM–MBD coupling, the influence of soil coverage and the compaction process on the seed position of the seeding monomer at different forward speeds are analysed. It was found that the adhesion between the soil and the soil-touching component can have a significant effect on the contact process between the component and the soil. Therefore, the EEPA model was used to analyse the soil–component interaction process and the contact parameters between the soil and components were obtained for the calibration. Further, based on the above work, it was found that before and after mulching, the displacement of seed particles of all shapes in the longitudinal direction increased significantly with the increase in the advancement speed of the sowing unit, while the displacement of seed particles in the transverse and sowing depth directions decreased with the increase in the advancement speed of the unit. In addition, before and after suppression, as the forward speed of the sowing unit increased, the displacement of seed particles of all shapes in the longitudinal and transverse directions gradually increased, and the displacement of seed particles of all shapes in the direction of the sowing depth decreased; the disturbance of seed displacement by the mulch suppression process was not related to seed shape. As the operating speed of the seeding unit increased, the mulching compaction process significantly reduced the sowing uniformity of maize seeds. This paper provides a theoretical basis for the next step in optimising the structure and working process of the soil coverage and the compaction.

During the operation of a shaped hole seed-metering device, poor seed-filling quality and inconsistent seed-casting points lead to poor seed spacing uniformity, especially in a one-chamber double-row seed-metering device. To solve this problem, a soybean double-row seed-metering device with double-beveled seed guide groove was designed to ensure a high single-seed rate and seed-casting point consistency. Through the theoretical analysis of the working process of the seed-metering device, dynamic and kinematic models of the seeds were established, and the main structural parameters of the seed discharge ring, triage convex ridge, shaped hole, and seed guide groove were determined. The main factors affecting the seeding performance were obtained as the following: the inclination angle of the triage convex ridge, the radius of the shaped hole, and the depth of the seed guide groove. A single-factor test was carried out by discrete element simulation to obtain the inclination angle of the triage convex ridge α3 = 29°, the radius of the shaped hole r1 = 4.16–4.5 mm, and the depth of the seed guide groove l1 = 0.49–1.89 mm. A two-factor, five-level, second-order, orthogonal rotation combination test was conducted to further optimize the structural parameters of the seed-metering device. The two test factors were the radius of the shaped hole and the depth of the seed guide groove, and the evaluation indices were the qualified rate, replay rate, and missed seeding rate. The results showed that the optimal combinations of the structural parameters were the radius of the shaped hole r1 = 4.33 mm and the depth of the seed guide groove l1 = 1.20 mm. Subsequent bench testing demonstrated that the seed discharge’s qualified rate was above 94% at operating speeds of 6–10 km/h, and the seeding performance was stable. The final results of the soil trench test showed that the seed-metering device exhibited a qualified rate of 93.31%, replay rate of 2.04%, and missed seeding rate of 4.65% at an operating speed of 8 km/h. This research outcome may serve as a valuable reference and source of inspiration for the innovative design of precision seed-metering devices.

In order to solve the problems of crop residue clogging, poor soil crushing and low operation efficiency under the stalks mulching condition, the traction combined machine for subsoiling and land preparation was designed. The optimization test was carried out to optimize the stalk cutting device and the soil crushing device under stalk mulching condition. The optimization test used a randomized complete block design, consisting of 10 treatments, in a 5 × 2 factorial arrangement. Each treatment included the combination of coulter types (8W, 13W, 18W, 25W and NW) and soil crushing roller types (with blade angle and without blade angle). The results showed that the combination of the fluted coulters with 8 waves and the soil crushing roller with blade angle was optimal. Finally, the verification test of the whole machine was carried out to evaluate the performance, and the results showed that the average value of subsoiling depth was 35.8 cm, the stability coefficient of subsoiling depth was 93.9% and the soil crushing rate was 53.7%. This research provides an important reference for the structure design of the large multi-functional combined machine for conservation tillage.