An air suction seeder has been widely used in the large-scale planting of rice, corn, vegetables, and rape, as well as the indoor factory seedling production, due to the high sowing accuracy, strong adaptability to seed size, low seed injury rate, high operating efficiency, and low cost of use. Among them, the seed metering device and air power system are two important core components of air suction seeders. Therefore, their operation can greatly contribute to the performance of the whole machine. It is also necessary for the stable air pressure supply and regulation in the air suction seed metering device pneumatic system. As such, the seeder can fully adapt to the sowing of various crops and have stable operation. Particularly, the multi-branch convergence pipe is the key component of the seeder pneumatic system. The cooperative operation of one seeder and multiple rows of seeders can be realized to converge the negative pressure tributaries that are generated by multiple seeders into the total flow and then conveyed them to the pneumatic system fan. The internal geometric structure can also be optimized to improve the working performance of the air suction seeder. The mechanical structure of the seeder is no longer the main reason for the increase in pressure loss in the pneumatic system and energy consumption of the fan. However, energy loss can be produced, when the airflow is more likely to mix with each other at the tee position at the junction of the multi-branch pipe header and the branch pipe, as the airflow of the pneumatic seeder is restricted by the geometric mechanism of the multi-branch convergence pipe in the process of spatial transfer. The accuracy and rationality of the piping structure can be the key issue to reduce the pressure loss and energy consumption of the pneumatic system. Therefore, it is essential to explore the pressure loss of airflow in the multi-branch convergence pipe and then to reveal the fluid motion state in the process of manifold piping for the low-energy multi-branch convergence pipe structure. In this study, a systematic investigation was implemented to clarify the flow mechanism of negative pressure airflow in the multi-branch convergence pipe of an air-suction seeder pneumatic system. The correlation characteristics were obtained between the total flow pressure loss and pipe geometry, in order to determine the quantitative prediction target value of total flow pressure loss. The flow state of the multi-branch convergence pipe was also analyzed to clarify the main influencing factors on the flow of the pipe. A single-factor experiment was performed on the Fluent simulation software. The flow mechanism was also established to explain the airflow pressure loss in the multi-branch pipe and the hydrodynamic mechanism from the microscopic perspective. The dimensional analysis was implemented to determine the pressure drop (ΔP, Pa) of outlet branch pipe and air density (ρ, kg/m³), dynamic viscosity (μ, Pa·s), length of the closed end of the header pipe (h, mm), the flow rate of inlet branch pipe (Q, m³/s), the inner diameter of inlet branch pipe (d, mm), length of inlet branch pipe (l, mm), spacing of inlet branch pipes (δ, mm), the inner diameter of header pipe (γ, mm), outlet branch pipe inner diameter (D, mm) and outlet branch pipe length (Δ, mm). The bench test results show that the application range of the established empirical equation formula were 0.0009 m³/s≤Q≤0.0045 m³/s, 28.0 mm≤d≤45.2 mm, and 100 mm≤ l ≤ 200 mm, 200 mm≤δ≤300 mm, 42.6 mm≤γ≤81.4 mm, 150 mm≤Δ≤ 250 mm, 34.0 mm≤D≤42.6 mm, and 53.6 mm≤D≤57.0 mm. The prediction accuracy of the total flow pressure drop can be controlled within 10% of the calculated by the empirical formula. The established empirical formula can provide a strong reference for the design selection and structure optimization of multi-branch convergence pipes of air-suction seeders.

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.

Weeds have posed a serious impact on rice growth and yield in paddy fields. In this study, an inter-row weeding device was designed in the paddy field, including a pressing-weeds floating plate and a weeding roller. The weeding procedure was that the floating plate pushed over the weeds in the inter-row area, and then the weeding roller pressed the weeds into the soil. The probability that the weeding roller pressed the weeds into the soil was improved by 9.98% after the floating plate was pushed over the weeds. Furthermore, the pressing-weeds floating plate was in a closed box structure, which gradually pushed over the weeds, reduced the forward resistance and moved the rice for less damage to the stems and leaves. The weeding roller was composed of weeding discs and weeding cutter teeth. The weeds were pressed into the soil to isolate them from sunlight and air, in order to achieve the purpose of weeding. The two ends of the weeding roller were equipped with the chamfer, in order to reduce the damage to rice roots. The weeding width was expanded by 3%, compared with the regular weeding roller. Some parameters were determined, including the expanded weeding width, chamfer angle, soil depth, root crown root angle and weeding width of the weeding roller. The simulation test was implemented to clarify the interaction between the weeding device and soil. The quadratic orthogonal rotation combination test was carried out to analyze the effect of the weeding depth and weeding speed on the amount of heaped soil on the floating plate, the amount of soil disturbance, and the force of the floating plate and weeding roller in the horizontal and vertical directions. The interaction relationship between the factors and test indexes was determined by variance significance and response surface method (RSM). As such, the optimal weeding parameters were determined: the weeding depth was 35 mm, and the weeding speed was 0.8 m/s. The field experiment was conducted to analyze the effects of different weeding modes on the plant height, yield, and roots of rice. Four treatments were set: non-weeding, chemical, artificial and mechanical weeding using this inter-row weeding device. Among them, three widths of weeding roller 150, 175, 200 mm and two types with/without chamfer were selected in the weeding rollers. A systematic investigation was made to determine the effect of different types of weeding rollers on the weeding rate, rice roots, rice growth and yield. The experimental results showed that the weeding rate of the device reached 87.51%, which fully met the requirements in the paddy field. The weeding device was also used to turn the soil and increase the permeability of the soil. The weeding rate increased gradually with the increase in the width of the weeding roller. There was an increase in the weeding rate of 7.3 percentage points by expanding the inter-row weeding area. There were also significant effects among different weeding modes on the plant height and yield of rice（P＜0.05）. Mechanical weeding can be expected to promote the growth of rice. The yield can also reach or even exceed the levels of chemical and artificial weeding. The weeding roller with different parameters has a significant impact on the weeding rate, plant height, yield and roots of rice. The weeding roller with chamfer at both ends when increasing the width of the weeding roller can effectively avoid or reduce damage to the roots of rice, for better growth of rice, yield and weeding performance（P＜0.05）. The inter-row weeding device can provide a strong reference to the design of weeding machinery and equipment in paddy fields.

An air-suction seed metering device has been widely used for precision planting in various crops, due to the minimal seed damage, high efficiency, simple structure and strong adaptability. Single-seed broadcasting has been one of the most important capabilities to improve the quality of hybrid rice planting, particularly with the direct seeding of hybrid rice and the seed production levels. However, the stable filling and high precision of single seed broadcasting are highly required to meet the large amount of sowing in the air-suction seed metering device in recent years. In this study, an improved air-suction single-seed metering device was proposed with rectangular suction holes and auxiliary seed filling. Taking the "Yoshida" hybrid rice as the research object, the gravity distribution of the seed was analyzed to optimize the structure parameters. It was found that the high adhesion of the seed depended mainly on the rectangular shape of the seed suction hole on the seed-sucking plate. According to the fluid-solid coupling theory in CFD-DEM, Ansys Fluent and Rocky Dem software were used to simulate the airflow part of the planter and the interaction between the planter and seeds. A CFD-DEM simulation model was then established to exchange data for the air-suction single-seed metering device. Five types of single-factor experiments were conducted with the seed suction holes in the same area. The drag force, pressure gradient force, and air-suction force were taken as the experimental indicators. The seed suction hole with the maximum air-suction force was optimized as the size of 0.8 mm × 2.25 mm. In this case of the seed suction hole, the auxiliary filling angle, working speed, and working pressure were selected as the experimental factors, with the single rate (S), multiple rate (M), and leakage rate (L) as the experimental indicators. The optimal ranges of auxiliary filling angle, working speed, and working pressure were determined to be 70°-90°, 30-60 r/min, and 400-800 Pa, respectively. Subsequently, the Box-Behnken experimental design was conducted to combine with the variance analysis, response surface method, and multi-objective optimization. The variance analysis indicated that the primary and secondary influencing factors on the single rate were the auxiliary filling angle, working pressure, and their interaction term. The primary and secondary influencing factors on the multiple rate were the auxiliary filling angle, working pressure, the interaction term between the working speed and working pressure, and the interaction term between the auxiliary filling angle and working pressure. The primary and secondary influencing factors on the leakage rate were the auxiliary filling angle, working pressure, and the interaction term between the auxiliary filling angle and working speed. The response surface analysis showed that the single rate had a strong correlation with the interaction term between the working pressure and auxiliary filling angle. The multiple rate had a strong correlation with the interaction terms between the working pressure and auxiliary filling angle, as well as between the working pressure and working speed. The leakage rate had a strong correlation with the interaction term between the auxiliary filling angle and working speed. The multi-objective optimization showed that the better performance of the seed metering device was achieved in a single rate of 86.91%, a multiple rate of 9.46%, and a leakage rate of 3.63%, when the auxiliary filling angle was 80.90°, the working speed was 42.65 r/min, and the working pressure was 621 Pa. The experimental verification showed high consistency with the optimized, with a single rate of 10.23%, a multiple rate of 9.46%, and a leakage rate of 3.41%. The research findings can provide better guidance to optimize the air-suction single seed metering device, in order to improve the overall operational accuracy for direct rice seeding machines.

The primary aim of this study was to classify the hazard level of brown planthopper (BPH) damage in rice. Three datasets, including spectral reflectance corresponding to the sensitive wavelengths from rice canopy spectral wavelengths, rice stem spectral wavelengths, and fusion information of rice canopy and stem spectral wavelengths were used for BPH hazard level classification by using different algorithms. Datasets and algorithms were optimized by the BPH hazard level classification effects (which was evaluated by indices of accuracy, precision, recall, F₁, and k-value). The optimized algorithm combination was used to build a hazard level classification model for spectral reflectance corresponding to the sensitive wavelength from the rice canopy spectral images. Results showed that: (1) The spectral reflectance corresponding to the sensitive wavelengths of fusion information dataset performed best in BPH hazard level classification, with the highest accuracy (99.08%), precision (99.31%), recall (98.83%), F₁ (0.99), and k-value (0.99). (2) The optimum algorithm combination was Savitzky-Golay (S-G) smoothing, principal component analysis (PCA) for sensitive wavelength selection, and broad-learning system (BLS) for modeling. (3) The spectral reflectance corresponding to the sensitive wavelengths dataset of rice canopy spectral images achieved accuracy (80.63%), precision (80.28%), recall (77.03%), F₁ (0.79), and k-value (0.74) in classifying BPH hazard level by using the optimum algorithm combination.