Precision agriculture can play an important role in the development of intelligent agricultural machinery, due to fertilizer saving, low labor intensity, and high work efficiency. Among them, the amount of fertilizer discharge can directly dominate the crop yield. Nevertheless, the fertilizer discharge device was in a closed state during the live broadcast operation. Therefore, the detection of particle fertilizer discharge has been one of the development trends of intelligent and precise operation. Various approaches have been developed to replace granular fertilizers in recent years, such as the rotational speed, doppler effect, dynamic weighing, photoelectric, visual, and electrostatic ones. However, the low accuracy of detection has limited in the rapeseed mechanical direct seeding, due mainly to the large and disordered flow of fertilizer particles. There is a high demand for the real-time detection of high-throughput granular fertilizers during high-speed operations. In this study, the high-throughput particle flow dispersion and diversion serialization of "collision dispersion +sieve diversion +spiral tube constraint" were proposed to fully meet the agronomic requirements of fertilization and high-speed operation in rapeseed direct seeding operation. The high detection accuracy was also obtained under the large and disordered flow of fertilizer particles. A parallel detection device was designed for the diversion order of granular fertilizer using the discrete diversion order mechanism. The key parameters were then determined for the sensing detection structure, uniform fertilizer tube, sieve diversion structure, and spiral tube. A multi-channel signal synchronous acquisition system was also designed for the detection device of rapeseed live broadcast granular fertilizer, according to the multi-channel parallel detection and sensing. A test bench was constructed using a spiral disturbance cone centrifugal fertilizer feeder. The device performance tests were conducted to verify the effectiveness of discrete diversion serialization. The results showed that there was a gradual decrease in the coefficient of variation for each channel diversion of the detection device in an inclined state, as the speed increased when the speed of the fertilizer discharger was 100-130 r/min (fertilizer discharge frequency 361.80-631.60 Hz). The coefficient of variation exceeded 6.08% for each channel diversion under normal field operation with an inclination of 0°-5°. Once the discharge frequency of single-channel fertilizer was 30-80 Hz, the accuracy of the detection device with the spiral tube increased by 7.3 percentage points, compared with the straight tube. The detection accuracy was not less than 90.11% within the speed range of 100~130 r/min after displacement compensation, which was 9.3 percentage points higher than before. The experiment of vibration fertilizer discharge showed that the low-frequency vibration (0-30 Hz) significantly improved the discretization of granular fertilizer and detection accuracy. There was a stable detection accuracy of intermediate frequency vibration (30-110 Hz). High-frequency vibration (110-150 Hz) broke the serialization constraint of granular fertilizer for low detection accuracy. There was no significant impact of different vibration frequencies on the uniformity of the flow distribution in the detection device. The coefficient of variation exceeded 4.98% for each channel diversion. Field experiments showed that there was no significant impact of the light, vibration, and dust on the detection device under normal field operating speeds of 4.3-7.0 km/h. The detection accuracy of the device was not less than 90.05% when the speed of the fertilizer discharger was 100-130 r/min. The detection device can be expected to detect the fertilization operation of the equipment, in order to improve the quality of fertilization operation.

High-speed rapeseed sowing has been confined to the high seed flow, low detection accuracy, and short battery life. In this article, a solar-powered device was proposed to detect the high-speed seed flow during rapeseed sowing, in order to improve the sowing efficiency and quality. Multiple channels of seed flow falling and synchronous detection were achieved during high-speed sowing. According to the requirements of agronomy and detection accuracy, 8 low-flux seed flows were divided during high-speed sowing. An 8-channel diversion structure was then designed to independently detect the seed flow. The photoelectric technologies were adopted to combine with the LED array light source and silicon photocell structure. A ring circuit board was integrated with eight channels using surface mount technology. The signal was accurately processed in each channel. Each circuit board was integrated with the detection functions, in order to monitor the status of seed flow in real time. The data support was then offered for the precise control of seeding operations. Furthermore, the optimal parameters were selected to design a boost circuit and solar charging control module in the solar panels. These components together formed an efficient solar energy system, providing a stable energy supply for the detection device. A series of tests were carried out to determine the parameters of each key component in the system. The high reliability and stability were then obtained after optimization. The bench test showed that the accuracy of the 8-channel device was achieved above 97.53% to detect the rapeseed sowing amount, which was 10.03 percentage points higher than the original 4-channel when the sowing frequency of rapeseed seeds was in the range of 60-130 Hz. The performance of detection was significantly better than that of the single- and 4-channel devices. Road tests show that the accuracy of the detection device for the rapeseed sowing rate remained stable at over 97.53% at the operating speeds of 10.3-15.7 km/h (78.9-123.5 Hz). Further field experiments verified that the accuracy of rapeseed sowing detection was not less than 97.07% at the high-speed operating speeds of 10.3-15.7 km/h (81.45-120.2 Hz). The sowing detection device was relatively stable. The accuracy of the detection was 0.46 percentage points lower in the field than on the road, due mainly to the influence of dust in the field. In terms of endurance time, the plug-in circuit board device worked continuously for 6 h, when powered only by a lithium battery. While the surface that mounted the circuit board device was worked for 7 h after optimization. After loading the solar energy, the device was achieved in the unlimited endurance on sunny and cloudy days. The endurance time also reached 72 h in the overcast weather. This finding can also provide data support for the precise detection of seed flow in high-speed rapeseed sowing, thus improving the endurance of the detection.

Fertilizers play an important role in soil fertility for crop growth. However, the excessive use of fertilizers often cause serious damage to the environment. Precision fertilization can be expected to significantly reduce the excessive use of fertilizers in farmland. An accurate and rapid detection of the fertilizers is also required for precision fertilization during operation. Previous research has been conducted on the stable, accurate, and reliable detection of high-flow granular fertilizers during field fertilization, in order to improve the quality of field fertilization and the utilization rate of fertilizers. However, fertilization agronomy is often required for the optimal speed in the field operation of the rapeseed direct seeder. Furthermore, there is a high application amount of granular fertilizers, particularly with the high frequency of the fertilizer discharge. At the same time, the sensor is dependent mainly on the type of fertilizer and environment. It is quite difficult to realize the high-precision real-time detection during mechanical direct seeding. Among them, capacitance has been widely used in detection devices during sowing, fertilization, and harvesting in precision agriculture. The high sensitivity can be expected for the simple design, stable and reliable operation. The device with the capacitance can share outstanding advantages, in terms of the mass flow rate of the granular fertilizer application. But it is still required for the high stability and dynamic measurement accuracy in the field environment. This study aims to improve the real-time accuracy of the detection during rapeseed direct seeding, due to the large amount of discharge of granular fertilizer, diversified types, and the sensitive components of the sensor. A non-contact capacitive device was also developed to detect the discharge and application of the granular fertilizers in the direct seeding machines. A self-calibration function was then used for the detection. The key structural parameters of the capacitive plates and isolation sleeves were designed to extract from the capacitive signals using simplified Kalman filtering. The key parameters of the filtering were determined after experiments. There was a relationship between the mass flow rate of the granular fertilizers and the capacitive signals. A three-point fitting calibration was proposed to detect the mass flow rate of granular fertilizers suitable for the different temperature environments and types of granular fertilizers. An 8-channel device and a terminal were then developed for the discharge and application of the granular fertilizers in rapeseed direct seeding machines. The bench tests show that the detection accuracy rate of the device was less than 97.35% under the environmental temperatures of 15, 25, and 35 °C. Specifically, the accuracy rates were less than 96.45% and 96.23% for the Xiangyan and Haosite compound fertilizers, respectively; The accuracy rate of the system was less than 95.62% when the speed of the seeding was 4-12 km/h and the average flow rate of the fertilizer discharge was 9.52-29.05 g/s. The field tests show that the accuracy rate of the system was less than 93.14% when the discharge amount of the granular fertilizer was 9.82-28.99 g/s. There was at least 3 percentage points higher than that of the existing granular fertilizer flow. There was accurate, integrated, and stable data transmission between the system and the cloud database. The vibration of the machine and dust also shared little impact on the detection. This system can provide an effective means for the evaluation of fertilization quality.

Planned operation paths can often result in the relatively low field turning efficiency of the machinery, particularly in the current path planning for unmanned oilseed rape sowing with intelligent agricultural machinery. Furthermore, the path planning cannot consider the fuel consumption during turning and the mid-operation replenishment of seed and fertilizer boxes, leading to low overall operation economy. In this study, an optimal path was proposed to consider the mid-operation resupply (OPCMR). Firstly, the fish-tail and U-shaped turning models were often adopted to alter the rows in rectangular fields. Different specifications were further classified according to the number of rows between operations. The fuel consumption curves of the machinery were measured under different states during turning. Secondly, the two turning models were constructed using the maximum turning radius and working width of the machinery. A turning cost function was also established with the turning time and fuel consumption of the machinery. The turning models were taken as the constraints. The slow convergence and easy trapping were confined to the local optimal solutions of the conventional ant colony algorithm (ant colony optimization, ACO). The conventional ACO algorithm was integrated with the simulated annealing algorithm and the heuristic factor of the ACO algorithm. An improved ant colony algorithm was obtained (improved ant colony optimization, IACO). Thirdly, the optimal operation path was generated with the least turning time and fuel consumption using the turning cost function and the IACO algorithm. The function was added to manually arrange the field entrance in the path planning, thus considering the uncertainty of the field entrance position. The first operation of the planned path started from the position closest to the field entrance. Finally, an autonomous seed and fertilizer replenishment control system was proposed for intelligent agricultural machinery. The key parameters were determined, such as the capacity of the seed and the fertilizer box of the combined seeding and fertilizing machine, as well as the per mu sowing and fertilizing amount in the field operation. Furthermore, the specific path interruption points were generated on the optimal operation path. These points were connected with the pre-set seed. The fertilizer replenishment stations were generated with the specific seed and fertilizer replenishment paths. Once the seed and fertilizer of the machinery were insufficient, the seed and fertilizer replenishment station was shifted along the path for replenishment, and then returned along this path to continue the operation. The results show that the IACO algorithm reduced the number of iterations by up to 56.9%, compared with the ACO algorithm. The minimum turning cost value was reduced by up to 2.82%, effectively avoiding the slow convergence and easy trapping in local optimal solutions of the ACO algorithm. The seed and fertilizer replenishment path tracking experiments show that the average distance between the machinery parking point and the seed and fertilizer replenishment station was no more than 0.5 m, and the average initial deviation was no more than 0.03 m when the machinery entered the next operation row. The seed and fertilizer replenishment control effectively realized the seed and fertilizer replenishment task without interrupting the operation of the next row. Compared with the conventional comb-shaped operation path, better performance was achieved in the unmanned agricultural machinery along the OPCMR path, with a 17.5% increase in the turning efficiency, a 9.8% reduction in turning fuel consumption, and a 94.7% reduction in human resource input after operation. The path planning effectively improved the operation efficiency to reduce the resource input. This finding can provide the technical support to construct the unmanned oilseed rape farms.

Precision fertilization can greatly contribute to the utilization rate of chemical fertilizers and ecological safety. The amount of chemical fertilizer can also be reduced for the rational demand of agricultural production. Among them, the fertilizer ejector is one of the most important components during precision fertilization. Its performance is of great significance to improve the quality of granular fertilizer application. However, the existing research focuses mainly on the structural optimization of the fertilizer ejector for the better fluidity of fertilizer particles. It still lacks the precision, the lag of fertilizer discharge, and easy clogging of granular fertilizer at the same time. In this study, a variable-diameter pneumatic-driven discharger of precision fertilizer was developed to integrate "discharge opening adjustment + rotational speed control + pneumatic forced discharge". The high accuracy was achieved to mitigate the fertilization hysteresis under varying operational speeds, in order to fully meet the agronomic requirements across different field plots during mechanized direct seeding of rapeseed. A systematic optimization was also carried out on the key parameters of the variable diameter structure, air-fertilizer mixing device, airflow distribution, and fertilizer guiding structure. The discharge tests were also conducted to calibrate the system. A control model was established to correlate the fertilizer discharge rate with the rotation speed and discharge opening. Dual-variable precision fertilization was implemented. The tests demonstrated that the optimal discharge range of 4.27-61.41 g/s was achieved with rotation speeds of 30-120 r/min and openings of 15-25 mm, fully meeting the operational requirements for the rapeseed direct seeding at the speeds of 2.5-12.0 km/h and the fertilization rates of 225-600 kg/hm². There was a high accuracy of fertilizer discharging of 96.30%-98.66%. The coefficient of variation for the consistency and stability of displacement in each row (C_v1) of 2.58%-8.62% and the same industry (C_v2) of 2.81%-6.85% fully met the national standards. Furthermore, the pneumatic-driven discharger eliminated the blockages in the operational range of 3.25-61.25 g/s. Specifically, the fertilizer particle velocity was enhanced by 44%, whereas, the discharge time was reduced by 44%, compared with the non-pneumatic ones. A field test confirmed that the high accuracy of fertilization was achieved over 95.07% via the precise control of opening and rotation speed, particularly under the fertilization rates of 300-600 kg/hm² and the operational speeds of 3.2-12.1 km/h. These findings can provide the technical references to develop the variable-rate fertilization equipment in rapeseed direct seeding.

Precision fertilization is one of the key technologies to control non-point source pollution in agriculture. Fertilizer reduction and efficiency technology can greatly contribute to green and sustainable agriculture in the rice-oil rotation region in the mid-lower reaches of the Yangtze River. Among them, fertilizer apparatus s have been focused mainly on the performance and optimization of structural devices. It is relatively lacking in the high speed and precision of fertilizer apparatus for rapeseed in real time. It is a high demand to optimize the precision fertilizer discharging for the reference value. The performance of fertilizer apparatus can depend directly on the accuracy of working components, in terms of uniformity and rational fertilization. However, the existing fertilizer apparatus cannot fully meet the range of direct seeding rapeseed of high-speed machines, due to the jam, low stability and distribution, as well as the serious crushing of particle fertilizer. In this study, an extrusion fertilizer apparatus for rapeseed was designed with a centrifugal cavity disc with high speed and precision. According to the agronomic requirements of high-speed direct seeding, the movement analysis of fertilizer particles was combined to determine the key parameters, such as fertilizer inlet, centrifugal cavity disc, fertilizer outlet, and power system. The discrete element software (EDEM) was used to establish the simulation model of fertilizer discharging. A systematic investigation was implemented to clarify the influence of the speed of the fertilizer apparatus on the torque of the centrifugal cavity disc, the average load, and the crushing rate of fertilizer particles. The results showed that the torque of the centrifugal cavity disc increased, whereas, the average load of fertilizer particles in the cavity disk decreased gradually, and the crushing rate increased below 0.80%, with the increase of the speed of fertilizer apparatus. The performance test showed that the speed of the fertilizer ejector was 30-120 r/min, and the displacement was 15.0-58.1 g/s, fully meeting the demand of high-speed direct seeding when the maximum fertilization amount was 600 kg/hm². The coefficient of variation was less than 8.58% for the consistent displacement in each row of fertilizer discharging, less than 6.45% for the stability of the displacement in the same industry, and the crushing rate was less than 0.89%; Specifically, the coefficient of variation was below 8.72% for the displacement consistency of each row shall under normal field operation with 0°~5° inclination. The comparative test showed that compared with the spiral perturbation, the fertilizer discharging with a centrifugal cavity disc was suitable for high-speed operation, where the crushing rate was reduced by 63.82%. There was no fertilizer jam when discharging fertilizer at high speed and large displacement. The field test showed that when the operation speed was in the range of 4.1-10.1 km/h, the coefficient of variation was not more than 6.72% for the consistent discharge in each row of the fertilizer ejector, while the coefficient of variation for the stability of the same row during fertilizer discharging was not more than 4.84%, and the relative error between actual and theoretical fertilizer discharging was less than 4.54%. The fertilizer discharging shared a wide range of displacement, smooth and stable operation, in order to effectively avoid the fertilizer sticking and the crushing rate in the process of fertilizer discharging. The fertilizer apparatus also fully met the demand for the high-speed direct seeding and precision fertilizer discharging of rapeseed.