Xianliang Wang

A high-speed centrifugal precision seed metering device for soybeans was developed to improve single-seed sowing accuracy under high-speed operation. The device integrates an involute deflector strip and ellipsoidal seed grooves, driven by a stepper motor to control the centrifugal disc and seed-metering wheel. Using EDEM software, a simulation model was established. A quadratic orthogonal design was applied with deflector type, disc speed, and seed-metering wheel speed as factors, and qualified seeding rate and miss rate as indicators. The optimal combination—disc speed of 49.01 r/min and wheel speed of 593.75 r/min—achieved a 92.08% seeding qualification rate and 1.91% miss rate. Bench tests confirmed strong agreement with simulation results, verifying the system’s reliability. This study offers a theoretical and practical reference for the development of high-speed precision metering devices for soybean planting.

Aiming at the problems of intensified soil compaction under the conditions of no-tillage operations and machine blockage caused by large-scale straw returning to the field, an operation mode of “straw strip collecting-strip subsoiling” was proposed, and a Monomer Profiling Strip Tillage Machine (MPSTM) with Straw-Strip-Collecting and Subsoiling Functions was designed to achieve anti-blocking operation and three-dimensional soil compaction reduction. The principle and mechanism parameters of monomer profiling in strip tillage are analyzed, and the effective profiling conditions are clarified. It is determined that the deflection angle, inclination angle, and installation spacing have a key influence on the straw clearance effect. The theory of soil failure and soil compaction reduction under the operation of the subsoiling and strip tillage mechanism is studied, and a combination of a medium-sized Subsoiler shovel handle and a 150 mm double-wing shovel is adopted. Using the EDEM discrete element method, taking the spatial parameters of the stubble clean disc (SCD) as the test factors and the straw removal rate (SRR) as the test indicator, a quadratic orthogonal rotation test is conducted to clarify the influence of each parameter on the straw clearance. The optimal SCD spatial parameters were determined as a deflection angle of 16.5°, an inclination angle of 25°, and an installation spacing of 100 mm, achieving a maximum SRR of 95.34%. Field test results demonstrated stable machine operation. Post-operation measurements yielded the following results: the width of the straw-cleaning band (WSCB) in the sowing strip is 193.7 mm; the overall straw removal rate (OSRR) is 84.82%, which is basically consistent with the simulation results; the subsoiling depth (SD) is 271.7 mm; the subsoiling depth stability (SDS) is 91.85%; the soil fragmentation rate (SFR) is 81.19%; and the reduction of soil compaction in the 0–10, 10–20, and 20–30 cm soil layer is 50.08%, 21.78%, and 40.83%, respectively. These results confirm that the machine effectively cleaned straw within the seeding band and reduced soil compaction, meeting the agronomic and technical requirements for strip tillage.

Stress transfers inside the soil during the traveling process of agricultural machinery, and the bonding of soil particles during this process is the main cause of soil compaction. In this study, the discrete element method was used to simulate the different responses of stress transfer and particle bonding in the soil under different times of tire passes in the tire-soil interaction process of agricultural machinery operation. It was found that from 1 to 8 passes, the increase in the times of tire passing caused the soil stress to transfer from the depth of 0.20 to 0.70 m, with the maximum stress reaching 27.36 kPa. The number of force chains between soil particles increased gradually with the increase in the times of tire passing, and the number of force chains risen from 12,058 to 14,515. This indicated that there was an inextricable link between tire passes and the formation of cumulative compaction in soil. The results of this study verified the validity of the DEM model based on PFC ^3D , providing a theoretical basis for the subsequent research on soil mechanical compaction technology for mitigating soil compaction caused by agricultural machinery and equipment.

Soil compaction alters soil structure, reduces soil air permeability, and adversely impacts crop growth. However, the rapid field detection of soil compaction remains a significant technical challenge. To address this issue, this study describes the development of an unsaturated soil bulk density measurement system based on soil air permeability, which enables the estimation of soil compaction through the measurement of soil air permeability. The system uses a specially designed soil probe that injects air into the soil at a constant pressure (P0) and flow rate (Q0). The steady-state air pressure (ΔP0) and flow rate (ΔQ0) at a radius r0 were recorded to calculate the soil gas permeability coefficient (ka). Laboratory experiments demonstrated a significant relationship between the soil gas permeability coefficient (ka), soil bulk density (ρ), and soil moisture content (w): soil compaction, which increases the bulk density, markedly reduces ka, while a higher soil water content further diminishes air permeability. Using experimental data, a bulk density estimation model was constructed with ka and w as independent variables. Field validation showed that the model achieved an accuracy of R2=0.72, thus demonstrating its reliability. This method is operationally straightforward, and allows for the rapid assessment of soil compaction. It provides a robust tool for precision field management and enhanced crop productivity.

Laboratory assessment of the effects of straw mulch on soil compaction under static and dynamic loads

The strip rotary tillage method effectively reduces the occurrence of straw clogging and creates a favorable seed bed environment. However, the mixture of crushed straw and soil in the seeding area results in inadequate seed-soil contact following compaction by the press wheels. A chisel-type opener furrow side pick-up blade was proposed to improve seed-soil contact by picking up wet soil from the furrow's side. The discrete element method was used to investigate the impact of earth blade surface parameters on soil dynamics. The key factors of the blade, including forward velocity, endpoint tangent angle, and angle of soil entry, were determined through theoretical analysis. Soil cover thickness and straw ratio in the seed furrow were evaluated using orthogonal rotation regression tests. The results show that the endpoint tangent angle and angle of soil entry have the greatest influence on soil cover thickness, while the angle of soil entry has the greatest influence on the straw ratio. The optimal values for the forward velocity, endpoint tangent angle, and angle of soil entry are 4.86 km/h, 107.17°, and 5.46°, respectively, resulting in a soil cover thickness of 40 mm and a straw ratio of 21.46%. Confirmatory soil bin tests showed similar results, with a soil cover thickness of 40.4 mm and a straw ratio of 18.03%. These results provide a viable solution for improving seed-soil contact after strip rotary tillage planter seeding.

Wheat sowing has the characteristics of wide and short sowing periods, and there are situations in which the suitable sowing period is missed. In order to meet the needs of high-speed sowing, a centrifugal wheat strip seeding device was designed, the principle of which is that rotating parts were mainly composed of centrifugal concave plate and guide strip rotating in the shell to provide the mechanical force and drive the airflow and then realize high-speed seeding. The influence of the rotational speed of the seed discharging plate, the seed feed rate, and the dip angle of the guide strip on the distribution of the flow field and trajectory of seeds in the device was analyzed. The aerodynamic characteristics of seeds and the distribution of the gas-phase flow field inside the seed displacer under airflow were analyzed by CFD–DEM coupled simulation. The effects of three operating parameters on the coefficient of variation of sowing uniformity (CVSU) and the row-to-row seeding amount coefficient of variation (RSCV) were clarified, and the simulation results were verified by bench experiments after secondary optimization. When the centrifugal concave plate rotational speed, seed feed rate, and guide strip angle were 408 rpm, 4938 grains/s, and 69°, the results showed that CVSU and RSCV were 1.12% and 2.39%, respectively, which was in line with the standards for grain strip seeders stipulated. The designed seed discharge device can sow 3.4 ha per hour. This study provides a reference for research of centrifugal airflow-assisted high-speed seeding devices for wheat.

In this study, a device was designed for tillage of compacted soil in wheel ruts formed by the repeated passage of agricultural machines.[Ed1] Soil parameters were measured, and then the wheel rut tillage device was divided into two parts, the soil lifting unit and the soil breaking unit, for separate simulation tests to study the tillage process. EDEM[Ed2] simulations were applied to the soil lifting device to compare and analyze the microscopic movement of the simulated soil particles and the operational resistance of the device. Analysis of variance (ANOVA) was performed using Design-Expert10 [Ed3] software to obtain the optimum combination of parameters of 125 mm device offset distance, 43.6° entry angle and 28° lifting angle. A full-factor test was conducted on the soil crushing device using EDEM coupled with RecuDyn multi-body system dynamics simulation software. The number of bond breaks and the traction resistance of the soil crushing device were used as the test indicators, and the optimum parameters were obtained for a soil crushing knife blade thickness of 6 mm and a cutting edge angle of 30° for the largest number of bond breaks and least traction resistance. The results of this study will provide technical support for the reduction of compaction zones in wheel ruts after tire travel on agricultural machinery in real time.

The traffic-induced soil compaction in the field has gradually become an important constraint to sustainable agricultural development. A field experiment was conducted to acquire the stress transmitted caused by multiple passes with different types of tractors and to investigate the impact of these stresses on soil bulk density and crop growth. The experiment applied two tractors with different masses: LOVOL M904 (HC) and John Deer 280 (LC), and six different treatments of 0 (C0), 1 (C1), 3 (C3), 5 (C5), 7 (C7), and 9 (C9) tractor passes for each tractor. The results showed that at each number of passes, tractors with small axle-loads at 0–20 cm depth generated higher soil additional stress, while tractors with large axle-loads at 20–80 cm depth generated higher soil additional stress. In the 0–20 cm soil layer, when the number of continuous passes is less than 7 times, the passes of a small axle-load tractor lead to larger soil bulk density, and when the number of continuous passes is more than 7, the compaction of large axle-load tractor leads to larger soil bulk density. At depths of 20–80 cm, compaction by large axle-load tractors results in larger soil bulk density. In this study, different levels of tractor compaction inhibited key growth indicators of maize, resulting in yield reductions. The effect of different tractor load compaction on maize yield increased significantly with the number of compaction passes, with 1–5 tractor passes having no significant effect on yield and 7–9 passes producing greater yield reductions for HC. This study will provide a theoretical basis and technical support for the selection of agricultural machinery and reasonable tillage technology.