Hydroponic lettuce is the main cultivated leafy vegetable in plant factories, and its scattered leaves are delicate and easily injured. Harvesting is an important process in the production of hydroponic lettuce. To reduce the injury level of hydroponic lettuce during harvesting, the impacts of the flexible finger-grabbing position applied on the grabbing force and the area of the injured leaves were investigated in this study by utilizing thin-film sensors and a high-speed video camera. According to the overlapping structural characteristics of adjacent leaves on lettuce, flexible finger-grabbing positions were divided into areas of the surface of the leaves and the intersections of the leaves. Three grabbing types—which are referred to in this paper as Grabbing Types A, B, and C—were identified according to the number of flexible fingers grabbing the leaf surface and the intersection area of the leaves. The force curves of all the flexible fingers were measured by thin film sensors, and the injury area of the leaves was detected using an image processing method. The results showed the consistency of the grabbing force curves and the motion characteristic parameters of the four flexible fingers. The maximum grabbing force of each flexible finger appeared at the stage of pulling the lettuce. The grabbing force of the flexible fingers acting on the intersection areas of the leaves was less than that acting on the leaf surface. As the number of flexible fingers acting on the intersection areas of the leaves increased, both the injury area of the leaves and the grabbing force decreased gradually. Grabbing Type C had the smallest injury area of the leaves: 120.3 ± 13.6 mm² with an 11.4% coefficient of variation.

Liquorice harvesting is the key process in the development of the liquorice industry. For harvesting liquorice with about 400 mm growth depth, a lightweight harvester with novel oscillating shovel-rod components was developed. Draft force, total torque, specific energy consumption, separation proportion, and soil structure maintenance were used to evaluate harvester performance under varied working conditions, and throw intensity and total torque were analyzed. A DEM model was developed to simulate the excavation and separation of soil. Three sets of single-factor simulation tests and one set of field tests were conducted. The results indicated that: Each 1 mm increase in amplitude decreased draft force by 463.35 N and increased total torque and specific energy consumption by 35.03 Nm and 4.3 kJ/m³, respectively. Each 1 Hz increase in vibration frequency increased specific energy consumption by 3.12 kJ/m³, while draft force and total torque decreased by 375.75 N and 28.44 Nm, respectively. Each 0.1 m/s increase in forwarding speed increased the draft force, total torque and specific energy consumption by 1302.72 N, 13.26 Nm and 3.82 kJ/m³, respectively. The main separation areas of the shovel-rod were front areas, where the soil separation proportion is greater than 60%, and the soil was completely separated at the end areas. The soils after harvesting had a relatively minimal disturbance in all layers, with soil structure maintenance greater than 0.61, and soil structure was well maintained. The liquorice plants were separated from the soil after passing smoothly through the oscillating shovel-rod components, during which the soil at different layers fell in sequence. This study revealed the interactive relationship between working components and soil, specifically the potential to maintain soil structure after harvesting. This new finding will assist in developing harvest techniques for rhizome crops with deep growth depth.

To investigate the interaction mechanism between agricultural tillage machinery and soil, this study established a precise simulation model by integrating physical and numerical experiments using typical yellow cinnamon soil collected from western Henan Province, China. The discrete element parameters for soils with varying moisture contents were calibrated based on the Hertz–Mindlin (no slip) contact model. Through Plackett–Burman screening, steepest ascent optimization, and Box–Behnken response surface methodology, a predictive model correlating moisture content, parameters, and repose angle was developed, yielding the optimal contact parameter combination: interparticle static friction coefficient (0.6), soil–65Mn static friction coefficient (0.69), and interparticle rolling friction coefficient (0.358). For the Bonding model, orthogonal experiments coupled with NSGA-II multi-objective optimization determined the optimal cohesive parameters targeting maximum load (673.845 N) and displacement (9.765 mm): normal stiffness per unit area (8.8 × 10⁷ N/m³), tangential stiffness per unit area (6.85 × 10⁷ N/m³), critical normal stress (6 × 10⁴ Pa), critical tangential stress (3.15 × 10⁴ Pa), and bonding radius (5.2 mm). Field validation using rotary tillers and power harrows demonstrated less than 6% deviation in soil fragmentation rates between simulations and actual operations, confirming parameter reliability and providing theoretical foundations for constructing soil-tillage machinery interaction models.

The vibration response of soil is a key property in the field of agricultural soil tillage. Vibration components of tillage machinery are generally used to reduce tillage resistance and improve work efficiency, and the pressure variation under low-frequency vibration will affect the fragmentation and dispersion of farmland soil. However, the gradient of pressure variation, frequency domain response, and effective transmission range is unclear. A new method based on the DEM (discrete element method) is presented to study the vibration response and pressure transmission under low-frequency vibration. Bench test results have shown that peak pressure positively correlates with the vibration frequency and attenuates rapidly at a vibration distance of 100 to 250 mm. The resulting data were also selected to determine the simulation model’s parameters. Amplitude, vibration frequency, and soil depth were used as test factors in single-factor simulation tests, and their effects on the peak pressure, frequency domain response, and effective transmission distance were analyzed. The results showed a positive relationship between the peak pressure and the test factors. The peak pressure increased with a maximum gradient of 19.02 kPa/mm at a vibration distance of 50 mm. The amplitude, vibration frequency, and soil depth positively correlated with the dominant frequency amplitude. The main frequency was independent of amplitude and soil depth. At a vibration distance of 250 mm, the dominant frequency was approximately twice the vibration frequency at 7–11 Hz and approximately equal to the vibration frequency at 13–15 Hz. Multiple exponential functions were used to fit the peak pressure attenuation function, obtaining an effective transmission distance range of 347.15 to 550.37 mm for the 5 kPa cut-off pressure. For a soil depth of 300 mm, the vertical shear wave diffusion angle was greater than the horizontal shear wave diffusion angle. This study clarifies the vibration response of soil under low-frequency vibration, which helps to design vibration-type, soil-engaging components of tillage machinery and match vibration parameters for energy-saving and resistance reduction purposes in soil tillage.

Straw cover is commonly used in agriculture to reduce soil water loss and improve crop productivity. However, the effects of straw length and cover amount remain unclear. This study, conducted from 2020 to 2022 in double-cropping (Laixi County) and mono-cropping (Qingyuan County) systems, examined the impact of straw length, cover amount, and tillage methods on soil properties, crop growth, yield, and water use efficiency (WUE). Five treatments were tested: no till (NT) with long and full straw cover (LF), long and half straw cover (LH), short and full straw cover (SF), short and half straw cover (SH), and no straw cover (NS). The results showed that straw cover improved soil temperature, crop growth, yield, and WUE. Under the NS treatment, the 30-day average soil temperature was 0–1.22 °C lower than with straw cover. Meanwhile, WUE increased by 2.38% to 5.52% under straw cover treatments compared to NS. Consequently, the straw cover treatments resulted in an increase of 2.28% to 6.89% in crop yield compared with the NS treatment. In double-cropping systems, SH treatment had the best results, while LF treatment was most effective in mono-cropping systems. These findings suggest that straw cover can enhance water conservation and soil quality while improving crop yields.

Hydroponic leafy vegetables have high yields, but their mechanized harvesting level is low. To improve the quality of orderly harvesting of hydroponic leafy vegetables, an ordered harvesting device with functions such as root flicking, posture adjustment and differential steering has been designed. A root-flicking method using rotating brushes was proposed, and experiments analyzed the effect of brush rotation direction. A posture adjustment method using a twisting conveyor belt was proposed, and experiments analyzed the impact of different twist angles on the stability of the adjustment process and the posture angle. A differential steering method using two pairs of conveyor belts with differential speeds was proposed, and experiments analyzed the impact of different steering belt speeds on steering stability and actual inclination angle. The root-flicking experiment results for hydroponic leafy vegetables showed that the counterclockwise followed by clockwise brush rotation combination performed better, with a root removal rate of 74.9%. The posture adjustment experiments on hydroponic leafy vegetables showed that the optimal twist angle for clamped and twisted conveyance was 35°, and the Mean Absolute Error (MAE) between the twist angle and hydroponic leafy vegetables posture angle was 0.38°. The differential steering experiment results indicated that the preferable belt speed difference for the directional conveyance of hydroponic leafy vegetables was 75 mm/s, and the MAE between the theoretical and actual inclination angles was 0.96°. Validation experiments based on posture adjustment and differential steering tests demonstrated a continuous harvesting success rate of 87.5%. This study provides valuable references for the design and development of orderly harvesting equipment for hydroponic leafy vegetables.