In-field hybrid rice nursing seedling, because of the low sowing rates, the existence of insufficient seed strip forming and seed uniformity in trays cause the problem of poor seedling quality and low planting uniformity. To solve the problem, this study presents a furrow opener with press roller for precision drill nursing seedling of hybrid rice. Based on the principle of rolling trenching and analysis of the interaction law between the rollers and subsoil of the seedling tray, ideal seed trenches suitable for hybrid rice precision seedling seeding was constructed. Coupled transplanting experiment was conducted to test the ditching effect. The specific structure and working principle of the furrow opener with press roller are described. The kinetics analysis among the press roller, load adjusting mechanism, seedling tray and subsoil, as well as the soil subsidence calibration test were conducted. The structure and parameters of the key components of furrow opener with press roller are designed and optimized. Discrete element simulation test and the Box-Behnken test method are conducted, the key parameters of the press roller was optimized using multi-objective optimization. Then, verification test is conducted to obtain the key parameters of the press roller with 100 mm of the diameter of the press roller, 45° of the V-shaped tooth angle, and 9mm of the ditch depth. Meanwhile, the verification tests show that the uniform qualified rate was 85.68% and strip forming qualified rate was 87.18%, which is consistent with the optimization results. The field experiments showed that compared with no-ditching drill sowing, the uniform qualified rate and the strip forming qualified rate of the ditching drill sowing increased by 5.78% and 17.17 %, respectively. The highest uniform qualified rate and strip forming qualified rate achieved 86.80% and 87.60%, respectively. According to the coefficient of variation of seedling quality, the consistency of seedlings was significantly improved. In-field rice mechanized transplanting, the missing plant rate of the ditching drill sowing decreased by 1.95%, the rate of 1-3 plants per pot increased by an average of 7.14%, and the root damage rate decreased by an average of 2.27%, compared with the no-ditching drill sowing. When the seeding density is 50, 60, and 70 g/tray, the theoretical yields of the ditching drill sowing were 234.90, 245.55 and 57.15 kg/hm² higher than that of no-ditching drill sowing, which increased by 3.12%, 3.53% and 0.80%, respectively. When the seeding density is 50, 60, and 70 g/tray, the actual yields of the ditching drill sowing were 381.60, 365.85 and 180.15 kg/hm² higher than that of the same sowing density with no-ditching drill sowing, with increased by 5.00%, 5.33% and 2.52%, respectively. The results of the study show that the furrow opener with press roller performs well and can effectively improve the technical level of precision strip seeding and precision coupling transplanting. The results of the study can provide a reference for the research and development of hybrid rice precision strip seeding equipment.

Rice is one of the most important food crops, with an annual planting area of approximately 30 million hectares in China. Hybrid rice accounts for about 50% of the national rice planting area, serving as a critical guarantee for the country's food security. However, the mechanized planting of hybrid rice has long been a challenge in the development of rice production mechanization and has not yet been fully overcome. To address this issue, a key approach is to adopt low seeding rates (50-65 g/tray) to cultivate robust blanket seedlings and achieve precise planting of 1-3 seedlings per hill by accurately controlling the seedling pickup amount of the transplanter. Nevertheless, due to the instability of longitudinal seedling feeding in transplanters, existing mechanized blanket seedling transplanting technologies have not yet fully achieved this goal. Currently, transverse seedling feeding in transplanters is primarily achieved using spatial double spiral cam mechanisms to ensure fixed-frequency (18, 20, or 24 times) quantitative delivery, which is accurate and reliable. In contrast, longitudinal seedling feeding relies on intermittent motion mechanisms to drive star wheels or ratchets, which in turn drive rubber-toothed seedling delivery belts. This process uses friction and the gravitational force of the seedlings to push the entire seedling mass toward the seedling pickup area. However, during longitudinal seedling feeding, factors such as machine vibration, the quality of the seedling blanket, and the moisture content of the seedling blocks can cause the seedlings to slide or become compressed and deformed in the seedling box. This leads to inaccuracies in longitudinal seedling feeding and subsequently affects transplanting quality. This study addresses the instability of longitudinal seedling feeding during mechanical transplanting of hybrid rice blanket seedlings. Based on the principle of forced seedling feeding with intermittent grids, a longitudinal seedling feeding method for mechanical transplanting of intermittent grid blanket seedlings is proposed. First, an intermittent grid blanket tray was developed to cultivate machine-transplanted blanket seedlings with intermittent grids (referred to as intermittent grid blanket seedlings). Second, using EDEM software and RecurDyn dynamics software, a physical model of the blanket seedling root-soil composite and the longitudinal seedling delivery belt of the transplanter was constructed. Combined with the mechanical parameter characteristics of blanket seedlings, a simplified DEM-MFBD dynamics model for longitudinal seedling feeding during mechanical transplanting of hybrid rice intermittent grid blanket seedlings was established, and longitudinal seedling feeding simulation experiments were conducted. Response surface methodology was employed to analyze the relationship between key parameters of the intermittent grid blanket tray and seedling feeding performance indicators, and tray parameters were optimized based on field experiments. Experimental results indicate: 1) Based on EDEM software, RecurDyn software, and experimental testing and analysis, a discrete element model of the root-soil composite body for hybrid rice blanket seedlings and a simplified model of the longitudinal seedling feeding components of the transplanter were constructed. Furthermore, a DEM-MFBD coupled simulation model for the dynamics of the longitudinal seedling feeding process was established, laying a foundation for exploring methods to improve the stability of longitudinal seedling feeding; 2) An intermittent grid seedling tray was designed, and a regression model between the longitudinal feeding stability and the main design parameters of the interrupted grid was developed. The optimal parameters for the intermittent grid were determined as follows: number of grids: 4, bottom inclination angle: 84°, and bottom length: 3.8 mm. Simulation studies indicated that the blanket seedlings cultivated in trays with this parameter combination significantly enhanced the stability of the longitudinal seedling feeding; 3) Field experiments and simulation results demonstrated that the optimized intermittent grid hybrid rice blanket seedlings exhibited higher operational stability and better transplanting quality during the actual planting process. Field tests confirmed that the simulation model was consistent with the field results, demonstrating reliable accuracy. Comparative analysis between traditional seedling trays and the intermittent grid trays showed that the blanket seedlings cultivated using the intermittent grid trays reduced the influence of their intrinsic parameters, decreasing the coefficient of variation (C_V) of longitudinal feeding by an average of 9.29 percentage points. The average qualified uniformity rates for hills with 1-3 seedlings and 1-4 seedlings were increased by 6.68 and 7.65 percentage points, respectively. The designed intermittent grid seedling tray significantly improved the stability of the longitudinal seedling feeding. The research findings provide a valuable reference for achieving hill-drop transplanting with fewer seedlings per hill in hybrid rice cultivation.