The uneven sowing of wheat on ground covered with rice straw in the rice–wheat rotation area in the middle and lower reaches of the Yangtze River has become a serious problem. Therefore, a test bed for throwing soil after sowing with a wide wheat seed belt was designed, which could complete the functions of straw crushing, straw lateral concentration and uniform sowing at one time. The discrete element simulation model of throwing soil after sowing with a wide wheat seed belt was established with rotary blade shaft speed, soil guide plate angle and soil retaining plate angle as variables. Taking the variation coefficient of wheat sowing depth and variation coefficient of sowing lateral uniformity as evaluation indexes, the effects of three variables on sowing uniformity were analyzed by single factor test and Box–Behnken test. The results of single factor test observed that when the rotating speed of rotary blade shaft was 260–300 rpm, the angle of soil guide plate was 36°–48°, the angle of soil retaining plate was 58°–74° and the experiment of utilizing a soil throwing and covering device with a wide seed belt after sowing revealed a good consistency of sowing depth and lateral uniformity effect. The Box–Behnken simulation experiment showed that the primary and secondary factors affecting the variation coefficient of wheat sowing lateral uniformity were the angle of soil guide plate, the rotation speed of rotary blade shaft, the angle of soil retaining plate and the angle of soil guide plate. When the rotation speed of rotary blade shaft, the angle of soil guide plate and the angle of soil retaining plate were 282.1 rpm, 42.4° and 65.5°, respectively, the soil throwing and covering device after sowing has the best seed-homogenizing effect. At this time, the variation coefficients of sowing depth and lateral uniformity in simulation test and field verification test were 4.35% and 4.57%, respectively, and 12.46% and 12.73%, respectively. The results of field verification test were basically consistent with those of the simulation test, which proved that the results of applying discrete element methods to optimize the soil-throwing device after sowing with a wide seed belt were credible. This study could provide a theoretical reference for the structure optimization of a soil-throwing device after sowing with a wide seed belt.

In recent years, there have been many studies on the calibration of soil simulation parameters; however, there are few soil parameters for wheat grown after rice that have been calibrated in the lower reaches of the Yangtze River, and the data from such calibrations remain inaccurate. Therefore, using the soil of Jiangsu as our research object, a soil parameter calibration was carried out based on the EEPA (Edinburgh elastoplastic adhesion) model and using the discrete element software EDEM (2020, DEM-Solutions, Edinburgh, UK). The depression depth measured via a uniaxial compression test and the maximum crushing force measured via an unconfined compression test were taken as indexes. The Plackett–Burman test was used to screen seven influencing factors (recovery coefficient, static friction coefficient, rolling friction coefficient, surface energy, contact plastic deformation ratio, tensile exp, and tangential stiff multiplier). The recovery coefficient and static friction coefficient were analyzed using a central composite test with depression depth as an index. The surface energy, plastic deformation ratio, and tangential stiffness factor were analyzed via a Box–Behnken test, with the maximum crushing force as the index. Taking the measured depression depth of 3.36mm and the maximum destructive power of 210 N as the target, the following final data were obtained—recovery coefficient: 0.322, static friction coefficient: 0.676, rolling friction coefficient: 0.5, surface energy: 17.158, contact plastic deformation ratio: 0.358, tensile exp: 2, and tangential stiff multiplier: 0.8. Finally, the simulation value and the actual value of the parameter group were verified and compared. It was found that the mismatch coefficient R² of the actual value and the simulation value is 93.509%. The mismatch coefficient R² between the actual and simulated values of unconfined compressive test is 94.2%. This shows that the curves obtained from the real test and simulation test have a high similarity. This study can provide technical support for the simulation and optimization of growing wheat after rice seeding equipment in the lower reaches of Yangtze River in China.

The soil during the sowing period of wheat after rice stubble cannot be accurately described by existing models and parameters with DEM because of its high moisture content and strong viscosity. The purpose of this study is to conduct an overall simulation of high-viscosity paddy soil and to analyze the accuracy of the model. Based on the results of an unconfined compression test and shear test, the range of bond parameters is preliminarily determined by a simulation test. Through the P-BD test and RSM test, the parameters with significant influence are determined to be normal stiffness per unit area (S_N), shear stiffness per unit area (S_S), and critical shear stress (C_S), and an optimized combination of these parameters is obtained. Based on the optimized model, the error range and error generation mechanism of the model are analyzed under different operating parameters. The results show that the optimal parameter combination is S_N of 1.07 × 10⁷ N/m³, S_S of 0.70 × 10⁷ N/m³, and C_S of 0.35 × 10⁵ Pa, corresponding to a compression force of 120.1 N and a shear force of 7.70 N. With an increase in forward speed or seeding quantity or a decrease in rotary plowing speed, the model accuracy tends to increase, and the range of relative errors was found to be from 8.8% to 28.4%. The results can provide a research basis for the study of the motion state of seeds under soil. It can also further enrich parameter data of soil discrete element simulation models and provide a reference for related research studies.

Waste plastic film often contains an abundance of impurities, such as crop stems and soil. To address this issue, a toothed-plate single-roller crushing device for waste plastic film was developed. By analyzing the movement and force pattern of the film, the feeding speed, the number of toothed plates, and the crushing roller rotation speed were used as test factors, and the size qualification rate and the impurity content of the crushed film were used as test indexes. Through a Box–Behnken test design, regression analysis, and ANOVA, a model between factors and indexes was established. The results showed that the size qualification rate and the impurity content of the crushed film were 82.55% and 9.57%, and the errors in the prediction and test values were 6.14% and 8.38%, which proved them to have good reliability. The findings of this study provide essential technical and equipment support for the resource recovery of waste plastic films.