Rice and wheat are two types of the most significant food crops for the national food security in China. Among them, the quality of sowing operations can dominate their high yields. A furrow opener can be closely linked to the performance of these operations during sowing. However, the commonly used double-disk furrow opener cannot fully meet the agricultural requirements for rice and wheat sowing at present, due mainly to the serious fluctuations in the furrow depth, inclined furrow walls, uneven furrow bottoms, and inadequate soil compaction at the bottom of the furrows. There is a high demand to prepare a more precise and uniform seedbed. In this study, a combined furrow opener was designed for the rice-wheat universal seeding. According to the cutting compression and slant cutting, the working resistance of the double disk opener was reduced to improve the overall quality of the furrow. The even furrow bottoms and normal furrow walls were suitable for the rice and wheat sowing. As such, a more favorable seedbed environment was provided to enhance the proper germination and growth of the rice and wheat seeds. A dual-layer furrowing technique was employed for better consistency in the furrow depth. A high-quality seedbed environment was obtained to support the healthy development of the seeds. Both the operational efficiency and sowing quality of the seeder were significantly enhanced after optimization. The key performance parameters were determined for the double disk trenching, sliding cutting, and retaining plates in the trencher. A comparison was then made on the difference in the ditching section area between the combined and double-disk opener. A series of simulations were carried out using EDEM software. The soil bin tests were then conducted to further validate the reliability of the simulation. The key indicators were selected to assess the performance of the opener, such as the working resistance, backfilling rate, and soil disturbance width. A single-factor optimization was performed to determine the optimal ranges for each key indicator, in order to fully meet the required standards of the performance. In addition, a Box-Behnken orthogonal experiment was conducted to analyze the interactions among various factors and their effects on the performance of the furrow opener. An optimal combination of the parameters was obtained for the furrow opener, that was the disc angle of 16°, the entry angle of 40°, and the vertical distance of 14 mm. The seeding quality and operational efficiency were further improved after optimization, the better seedbed was prepared, the field bin tests conducted with the optimal combination parameters yielded a working resistance of 105.5 N, a return soil rate of 41.3%, and a soil disturbance width of 108 mm, compared to the conventional double-disc furrow opener commonly used in rice-wheat rotation areas, the working resistancewas reduced by 13.74%, the return soil rate increased by 20.41%, and the soil disturbance width decreased by 6.25%. In conclusion, the combined furrow opener of the rice-wheat universal seeding was significantly improved in the sowing quality and operational efficiency. The theoretical analysis, simulation, and experiment also confirmed that better performance was achieved than that of the double-disk furrow openers. There was a more consistent and high-quality seedbed environment. The new opener can be expected to enhance the yield and overall success of the rice and wheat crops, thus contributing to the long-term food security of the nation. Therefore, agricultural equipment can fully meet the evolving needs of modern farming.

Direct seeding of rice is a green planting technique because it reduces irrigation water and lowers agricultural production costs. A vacuum seed meter with a double hole for rice was developed to improve the planting accuracy of direct seeding and to meet the tiny seeding rate. The key components of the vacuum seed meter were theoretically analyzed and designed. The optimal parameters of the seed disturbance structure were determined by the Box-Behnken test using the quality of feed index (each group of holes is 1 to 2), miss index, and multiple index as test indices. The results of the Box-Behnken test showed that the optimal parameters were a height of the seed disturbance structure of 1.65 mm, a diameter of the upper arc of 98.87 mm, and a central angle of the upper arc of 11.4°. Based on the optimal seed disturbance structure, the effect of the shaped hole structure parameters on the planting accuracy was investigated, and the optimal hole width and depth were determined to be 4 mm and 2 mm. CFD-DEM numerical simulations showed that the pressure gradient force on the seeds was greater than the drag force, and the pressure gradient force and drag force were positively correlated with the width of the shaped hole. When the rotational speed was 60 r/min and the vacuum pressure was 2.0 kPa, 2.4 kPa, and 2.8 kPa, the miss index of the vacuum seed meter with Wuyou 1179 as the test material was 3.52%, 2.5%, and 2.22%; the quality of feed index was 92.41%, 92.13%, and 87.13%; and the multiple index was 4.07%, 5.37%, and 10.65%. For Huanghuazhan and Taixiang 812 rice seeds, the planting accuracy of the vacuum seed meter with the double hole can meet the requirements for direct seeding of rice. This study provides a theoretical basis and design reference for rice precision planting technology.