Liquid fertilizer has many advantages, such as low production cost and little environmental pollution. Liquid fertilizer open furrow strip application method is widely used in fertilizer application operation. The widely used core-share furrow opener has a high operational resistance, disturbing the soil, hurting the crop roots, causing the liquid fertilizer to volatilize and deteriorating the fertilization effect. In this study, based on the streamline curve of the sturgeon body, we designed several bionic sturgeon liquid fertilizer deep application openers by combining bionics and analyzed the effects of several openers under different operating speeds on open furrow resistances and soil disturbance based on the discrete element method. The mechanism of open furrow resistances reduction and efficient soil backfill of the bionic structure were verified by indoor soil bin tests. The test results show that, compared with the core-share type furrow opener, both open furrow resistances and soil disturbance of the bionic sturgeon liquid fertilizer deep application opener are smaller. This study provides theoretical and practical references for the design of liquid fertilizer deep application openers.

The longitudinal axial flow threshing cylinder of the full feeding rice combine harvester is widely used in China and works with violent vibration. To explore the source of the excitation affecting the vibration and to reduce the vibration, a finite element modal analysis and multipoint input and multipoint output (MIMO) modal test were performed to solve the natural vibration characteristics. By analyzing the excitation frequency, we concluded that the main reason for the resonance was the coupling between the rotation frequency of the threshing cylinder and the first natural frequency. To avoid the influence of resonance and realize a lightweight design, we proposed a combination of size optimization and topology optimization. The second rotation orthogonal combination test was designed to analyze the first natural frequency, maximum stress, and maximum deformation of the threshing cylinder, and the threshing cylinder was reconstructed as a central symmetrical structure to balance the rotational inertia force. The field experiment results showed that the amplitudes of the optimized threshing cylinder were significantly lower than those of the original threshing cylinder. This study provides ideas for solving the vibration characteristics of rotating parts and provides an important reference for the design of vibration reduction and weight reduction of key parts in the field of agricultural machinery.

Liquid-fertilizer deep-application techniques are techniques for applying fertilizers to the root system of crops, which can effectively improve the utilization rate of fertilizers and reduce application amounts. Due to the soil viscosity of soils in the cold region of Northeast China, the soil return rate of furrow openers for liquid-fertilizer deep applications is low, which can easily cause excessive volatilizations of liquid fertilizers. Therefore, aiming at the operational requirements of low soil disturbance for liquid-fertilizer furrowing and deep applications, an efficient soil-returning liquid-fertilizer deep-application furrow opener was innovatively designed based on soil characteristics during the inter-cultivation period in the cold region of Northeast China. The discrete element method (DEM) was used to analyze the operating performance of the high-efficiency soil-returning liquid-fertilizer deep-application furrow openers, which is determined by key operating parameters including width and slip cutting angle. The DEM Virtual Simulation Experiment results show that the optimal combination is the width of 37.52 mm and a slip cutting angle of 43.27°, and the test results show that the optimal performance of the high-efficiency soil-returning liquid-fertilizer deep-application furrow opener is that the soil disturbance rate is 51.81%, and the soil-returning depth is 52.1 mm. This paper clarifies the relationship between the width and the slip cutting angle in furrowing resistance and soil disturbance and the mechanism by which the width and slip cutting angle affect soil disturbance. Above all, this study provides a theoretical and practical reference for the design of liquid-fertilizer deep-application furrow openers.

Liquid fertilizers are mainly applied by spraying liquid fertilizer on the surface of crop leaves and by deep openings between rows. The first causes considerable environmental pollution, and the second can easily cause to damage the root system of crops. In this study, corn crops were taken as the study object and an efficient deep-hole application method for liquid fertilizer based on alternate drilling was proposed. The needle body is driven by the spur gear wheel system in a caving mechanism to puncture holes alternately in a vertical posture and high-speed punctures are implemented with less disturbance to the soil. The cylindrical hollow cam of the mechanism is controlled so that the fertilizer needle sprays fertilizer when injected into soil and stops injecting when pulled out of the soil. Based on the bench test, fertilizer injecting performance and energy saving performance of the differential two-way fertilizer supply distribution device were analyzed and the head loss for energy saving value is 2.1, 3.1, and 5.5 m. Based on numerous field tests, the puncture track, hole width, and hole spacing are analyzed under different puncture speeds. Field tests were carried out according to a quadratic orthogonal rotating combination design and the results show that when the fertilization depth for agronomic requirements is 80 mm and the machine work speed and forward speed are 127 r min⁻¹ and 1.40 m s⁻¹, respectively, the hole width is 39.9 mm, the hole spacing is 320 mm. The efficient deep-hole application method for liquid fertilizer based on alternate drilling can provide support for data analysis and theoretical design of liquid fertilizer deep application technology for corn crops.