In the conventional straw returning operation, the maize straw is broken into pieces of about 10 cm and degraded naturally in the farmland. Under the conventional straw returning mode, maize straw does not easily decompose quickly in cold climate conditions, which can cause a significant decrease in the dry matter accumulation rate of next maize seedlings. Therefore, it is difficult to popularize conventional straw returning in the maize-growing regions of Northeast China. In order to solve the above-mentioned problems, a new agronomic technology of straw returning is proposed in this study, and a corresponding Bionic Straw Fine Crusher is developed to match the agronomic requirements. The key function of fine-crush straw returning is to significantly increase the contact area between the straw pith and the external environment by significantly shortening the crushing length, thus accelerating the rate of straw decomposition. In this study, the differences in operational effects between fine-crush straw returning, conventional straw returning, and no returning are clarified through 6 consecutive years of field experiments. At the same time, statistical analysis of the experimental data reveals the influence of fine-crush straw returning on the dry matter accumulation of maize at the seedling stage under the conditions of different returning modes, and determines the optimal agronomic parameter combination. The results of this study show that fine-crush straw returning significantly increased the decomposition rate, soil organic matter content, and soil accumulated temperature, thus creating a seedbed more favorable for maize seedling development. The experimental results showed that the optimal crushing length values of fine-crush straw returning were 1.5 cm, 3 cm, and 1.5 cm under mulching returning, shallow burial returning, and deep tillage returning conditions, respectively. Compared with conventional straw returning and no returning operations, the fine-crush straw returning operation can increase the maximum seedling dry matter accumulation of the maize crop by 5.1 g/plant and 2.8 g/plant (shallow burial), 4.2 g/plant and 1.8 g/plant (deep tillage), and 4.3 g/plant and 1.9 g/plant (mulching returning). The findings of this study may provide a viable new agronomic technology to accelerate the spread of straw returning in maize-growing areas of Northeast China.

Design and key parameter optimization of an agitated soybean seed metering device with horizontal seed filling

In disturbance-assisted seed filling vacuum seed-metering devices, the suction hole causes difficulty in quickly and stably sucking seeds when used for high-speed seeding and the large working negative pressure demand is used. To address this difficulty, this study’s authors designed a seed disk hole with a variable cross-section structure, and the groove depth, which has the function of assisting seed filling, was optimized. Using the combined method of Fluent numerical analysis and an orthogonal experiment, the influence of the shape, inlet diameter, and length of the seed disk hole on the pressure difference of the seed disk hole was analyzed. The working process of the vacuum seed meter was simulated and analyzed by the Discrete Element Method and Computational Fluid Dynamics coupling method. It was found that with the increase of the diameter of the seed disk hole, the pressure difference decreased, and the length of the seed disk hole had little effect on the pressure difference. The best diameter of the seed disk hole was 5.4 mm, and the length was 5 mm. It was found that the pressurization effect of the arc-shaped seed disk hole is better. With the increase of groove depth, the leakage rate shows a trend of first decreasing and then increasing, which was determined to be 1.5 mm. The verification experiment proved that the working performance of the optimized seed metering device is better than that of the original one. The results show that when the working negative pressure was 4 kPa and the working speeds were 8~14 km·h⁻¹, the qualified rate was not less than 95.0%, and the seed filling performance was relatively stable. The optimized vacuum seed metering device can be applied to high-speed seeders, while ensuring the requirements of high-speed sowing operations.