Furrow opener for the precision drilling nursing seedlings of hybrid rice

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.