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Grain qualities including milling, appearance, cooking and nutritional quality, are important traits that have aroused rice researchers' attention worldwide. Head rice rate, an important milling quality together with grain yield affects head rice yield. The head rice yield is directly related to economic value of the grains, and has significant impacts on income of rice producers. Precision rice hill-drop drilling is a simplified technique, which can achieve high yield while is applied at appropriate rice growth regions. The precision rice hill-drop drilling technique has been applied in many rice growth regions in China. Previously, precision rice hill-drop drilling technique has been proven to influence rice yield, agronomic performances and grain qualities in small region only and assessing the effect of precision rice hill-drop drilling technique on grain qualities in national wide is therefore important. In order to investigate the influence of precision rice hill-drop drilling technique on grain qualities in multiple rice growth regions in China, the comparison experiment were carried out. In this study, comparisons of the grain qualities between precision rice hill-drop drilling and machanical transplanting were investigated in the mainly planting areas (viz: Anhui, Shanghai, Guangdong, Sichuan, Xinjiang and Shandong) of precision rice hill-drop drilling in China. Results showed that precision rice hill-drop drilling technique was beneficial to improve head rice yield. Rice by using precision rice hill-drop drilling had higher head rice yield than that by using machanical transplanting in Nanling Anhui, Mianzhu Sichuan, Wensu Xinjiang, and Gaoqing Shandong regions, which increased by 9.11%, 27.02%, 4.08%, and 11.11% significantly. Moreover, the effects of precision rice hill-drop drilling technique on protein content and amylose content in grains from different investigated regions were different because of the difference in cultivars and environmental conditions, and the decrease in protein content and amylose content in grains were detected for some investigated regions. Furthermore, precision rice hill-drop drilling technique significantly decreased chalky rice rate in grains in Gaoqing Shandong, while showed no significant effect on appearance qualities of grains for other investigated regions. This study have investigated the impact of precision rice hill-drop drilling technique on grain quality of the rice varieties planted in large areas of the rice planting regions in China, this work is beneficial to further promotion to the popularization and application of precision rice hill-drop drilling technique in appropriate areas. [ABSTRACT FROM AUTHOR]

Compared to rice mechanistic metering device, rice pneumatic metering device has advantages of low number of sowing seeds, high precision of seed metering and low seed-injuring rate. Because the precision of seed metering is difficult to control and the performance of hill sowing is poor, rice pneumatic metering device is difficult to be widely used in field direct-seeding. The control of the precision of seed metering is the key to design metering device. Analysis of the process of dropping seeds helps improve the precision of seed metering and the performance of hill sowing, providing a basis for the design of metering device. Seeds were taken away from sowing disc under positive pressure for blowing seeds. The dropping trajectories and hill sowing performance of rice seeds were studied in this article. A high-speed photography technology was introduced to investigate how the dropping trajectories of rice seeds varied and what influenced the dropping trajectories, on which the equations of the rice's movement were formed. The theory equations were optimized through the average horizontal displacements of actual dropping trajectories and the optimization equations under the different conditions were obtained. The diameter of hill sowing was also measured. As seeds were taken away from sowing disc under positive pressure, seeds gained an initial velocity, which was called Vz and was vertical to the sowing disc. Because seeds moved along with sowing disc rotating before seeds were blown away, the seeds gained the other initial velocity, which was called Vr and was parallel to the disc. Seeds also gained acceleration of gravity under the gravity. In the above factors, the dropping trajectories were spatial parabolic, which was more complicated than the plane parabolic trajectories of rice mechanistic metering device. In order to investigate and count the dropping trajectories of rice pneumatic metering device, a coordinate system was established. Indic hybrid Peizataifeng was taken as research subject in this article, of which water content and average length, width and thickness were 20.5% and 8.97, 2.34 and 1.90 mm respectively. There were 2 dropping trajectories, the trajectory of frontal dropping seed and the trajectory of profile dropping seed. The dropping trajectories and diameters of hill sowing were analyzed by multi-factor experiment under different rotation rates and positive pressures for blowing seeds. The experimental results showed horizontal displacements of the trajectory of frontal dropping seed increased with the increasing of rotation rate, which were less than 5 mm. The frontal trajectory had good stability under positive pressure of 0.1 kPa, and horizontal displacements were stabilized within the range of 45-65 mm. Under positive pressure of 0.2 kPa, the frontal trajectory was unevenly distributed with bad stability. Trajectory of profile dropping seed was little affected by rotation rate. Horizontal displacements of trajectory of profile dropping seed increased with the increasing of positive pressure for blowing seeds. The profile trajectories were stabilized within the range of 0-15 mm under positive pressure of 0.1 kPa. Under positive pressure of 0.2 kPa, the profile trajectories were unevenly distributed. Diameters of the hill less than 50 mm were deemed as qualified, while diameters more than 50 mm were deemed as substandard. The probability of substandard diameter increased with the increased rotation rate and positive pressure. Performance of hill sowing was best with the rotating speed of 30 r/min and positive pressure of 0.1 kPa, of which qualified rate was 96.9%. The optimum height of dropping seeds was 10 cm. This article analyzed dropping trajectories in theory and got the optimal conditions of performance of hill sowing, providing the basis for optimal conditions of hill sowing and the reference for the design of seeding tubes of rice pneumatic metering device. [ABSTRACT FROM AUTHOR]

The technology of rice's mechanical direct seeding can significantly reduce the consumption of manpower and material resources, and meanwhile maintain the production of rice. Super hybrid rice is a kind of hybrid rice and its tillering ability is stronger than the general hybrid rice. Due to the characteristics of high tillering capacity of super hybrid rice, the sowing quantity is required to be 1-3 seeds for each hole when super hybrid rice seeds are directly seeded to the field by the drilling machine, so as to ensure the high precision of seeding and high rate of field seedling emergence. In order to meet the requirement of 1-3 seeds for each hole using the precise hill-drop drilling technique, a seed-filling stratified room was designed, which was between the seed-metering device and the seed box on pneumatic feed mechanism for precision rice hill-drop sowing. It also aimed at improving the liquidity of seeds and raising the seeding precision, the liquidity of rice seed would reduced after accelerating germination. This the reduction of the liquidity of rice seed after accelerating germination had so bad effects on filling process that it limited the improvement of metering performance. Indic hybrid Peizataifeng was taken as the research object, and the impacts of the seed-filling stratified room on the performance of the pneumatic feed mechanism was studied by the single-factor experiment and orthogonal experiment in this paper. These experiments were carried out under different negative pressures for sucking seeds and positive pressures for blowing seeds. The experimental results showed that there existed an optimization condition on the capability of the metering device to meet the needs of the production. The probability about the quantity for each hill was used to evaluate the capability of the pneumatic precise metering device. The seed-filling stratified room consisted of a barrel and two seed-guiding plates. The cross-section of the barrel was the square with 50 mm per side. There were the chutes on the lining of the barrel, which were 1.1 mm wide. Seed-guiding plates were 1 mm thick, which were connected with the barrel by chutes. The two seed-guiding plates formed an angle of 45 degrees. The optimization condition was that the sucking plate's rotation speed was 30 r/min, the negative pressure for sucking seeds was 1.6 kPa and the positive pressure for blowing seeds was 0.1 kPa. With the seed-filling stratified room, the probability of 1-3 seeds per hill for the metering device was 95.4%; in addition, the probability of empty seed was 1.53%, and the probability of greater than or equal to 4 seeds was 3.07%. Under the same condition, the probability of one seed per hill for the metering device was 17.32%; in addition, the two-seed probability was 58.72% and three-seed probability was 19.36%. Compared with the existed researches, the results showed that the seed-filling stratified room between the seed-metering device and the seed box on pneumatic feed device, had a good influence on the precision of the pneumatic seed-metering device, improved the fluidity of the seeds and decreased the friction force and extrusion force among the seeds. This study provides an important reference for the structure optimization and the performance improvement of the pneumatic metering device. [ABSTRACT FROM AUTHOR]

Deep fertilizing is a high efficiency fertilization method in rice fields. In order to realize deep fertilizing, according to the requirement of rice planting, a synchronous side deep fertilizing technique is developed on the base of a precision rice hill-drop drilling technique. By ditching, ridging, deep fertilizing, and seeding joint operations, the fertilizing ditch openers prescribe fertilizing ditches, and the fertilizer apparatus puts fertilizers into the fertilizing ditches which are between two seeding ditches, to provide fertility of the necessary growth for rice in the two seeding ditches. At the same time, the fertilizing ditches are covered by the skateboard. After covering, fertilizers can reduce the loss due to volatilization, denitrification, and leaching. And then the seeding ditch openers prescribe seeding ditches, and the seed-falling devices take rice into the seeding ditches, at the same time the water ditch openers prescribe water ditches, and the water in the water ditches will be provided for the rice in the seeding ditches. In order to explore the distribution of the depth of deep fertilizing and fertilizer in different soil layers, this paper investigated the special distribution of the rice root system in different planting patterns and rice varieties. The 80% rice root is in a 0-10 cm soil layer. Technical parameters for synchronous side deep fertilizing were studied based on the special distribution of the rice root system in that soil layer (0-10 cm). The optimum fertilization depth was identified as 10 cm. And according to the special distribution of the rice root in the 0-5 and 5-10 cm soil layers, fertilization distribution for the rice varieties of 'Peizataifeng' and 'Yuxiangyouzhan' in the 0-5 cm and 5-10 cm soil layers was researched. The field experiment results showed that the precision rice hill-drop drilling machine with synchronous side deep fertilizing developed in SCAU meets the requirements of the synchronous side deep fertilizing technique, which can be used as the implementation of a synchronous side deep fertilizing technique with precision rice hill-drop drilling. The field experiment results in rice production indicated that the technique can increase the yield and reduce the cost. Compared with the artificial fertilizing on the same fertilizing level, the higher effective panicle, grains per panicle, and seed setting rate were achieved with the synchronous side deep fertilizing technique. The rice yield increased by 418.5-957 kg/hm2 with an improvement of 5.86%-13.41%. The research results could provide the references for the design synchronous side deep fertilizing machine. [ABSTRACT FROM AUTHOR]

To accurately control the longitudinal relative position of a harvester and transport vehicle, such that grain in the harvester can be accurately unloaded into the transport vehicle's granary, this study established a master–slave collaborative harvesting system. Furthermore, this study proposed a calculation method for the longitudinal deviation of two vehicles, analyzed the structure and mathematical model of the hydraulic stepless transmission, identified the proposed stem transfer function of the hydraulic stepless transmission speed, analyzed incremental proportional–integral–derivative (PID), and developed self-adjusting–single-neuron PID control methods. Simulations and field experiments were performed to test the applicability of the proposed system. The experimental results indicated that the maximum overshoot of the longitudinal deviation between the harvester and the transport vehicle did not exceed 0.25 m, the steady-state mean absolute deviation did not exceed 0.08 m, the steady-state maximum deviation did not exceed 0.26 m, and the steady-state standard deviation did not exceed 0.09 m, when the harvester speed was 0.6, 0.8, and 1 m/s. Field-harvesting application experiments showed that the settling time during the alignment process was 13.2 s, and the steady-state maximum deviation was 0.253 m. The grain can be accurately unloaded into the granary of the transport vehicle. These results indicate that the control method and the master–slave collaborative harvesting system proposed in this study can meet the needs of precise collaborative unloading between the harvester and transport vehicle. [ABSTRACT FROM AUTHOR]

In order to meet the requirement of field direct seeding for super hybrid rice: 1-3 seeds per hill, a pneumatic rice direct-seeder with six seeding metering devices was designed. Transmission system of pneumatic rice direct-seeder and seed metering device were analyzed in this study. And the pipeline structure and vortex pump were designed and selected. The pressure distribution of the pipeline was tested. The pressure value of each sub-pipeline under the conditions of different main pipeline pressure value was obtained and the reasons for pressure loss were analyzed. The results showed that the variation coefficient between sub-pipelines was less than 5%. The pipeline pressure could be evenly distributed. Further, the field experiments were carried out on super hybrid rice Peizataifeng using two-factor testing, by which the effects of different negative pressure and different forward speed (namely, rotational speed of suction plate) for seeding precision were studied. It found that: (1) the optimal negative pressure was 2 kPa; (2) under the optimal negative pressure, the probabilities of 1-3 seeds per hill for the direct-seeder were 93.41%, 95.47% and 97.50%, respectively, when the forward speed of the direct-seeded was high, medium and low speed; (3) the probability of empty hole was less than 2%, which satisfied the field direct seeding requirements of super hybrid rice. Additionally, hill spacing was measured, and the factors affecting the hill spacing were analyzed. The results showed that the fluctuation of hill spacing in the small range will not affect the seeding effect. In this study, a new type of pneumatic rice direct-seeder was designed. The main working components were tested and analyzed. The best parameters of field work were obtained. It provides the basis for the field application of the pneumatic rice precision seeder. [ABSTRACT FROM AUTHOR]

• The direct-seeding path for rice covers the entire field. • Rice direct-seeding path includes the encircling path around the field blocks. • Encircling path planning algorithm is applicable to different shapes fields. • The path planning encompasses various patterns and path sequences. Path planning is one of the key technologies that determines the efficiency and quality of field operations using autonomous agricultural machinery. To date, there has been extensive research on global coverage path planning for unmanned agricultural machinery within the working area; however, the issue of "encircling and edging" left by the machinery during headland turns is often overlooked. This study focuses on the operational conditions of unmanned agricultural machinery in the rice fields of southern China. The path planning problem is abstracted under physical constraints, such as the space at the field headland, the agricultural environment (e.g., types of field ridges), the turning characteristics of the machinery, turning radius, working width, and minimum safety distance, into mathematical constraints. This yields an optimized path planning model and sequence combination. Based on the improved Reeds–Shepp curve, an en-circling and edging path planning algorithm is designed. The planned path for the unmanned agricultural machinery from start to finish consists only of arcs and straight lines, suitable for the right-angle turning, reversing, and 180° U-turn operations required for rice field machinery, thus significantly improving the coverage of field edges and missed areas at the headland. A rice direct-seeding machine was used as a test subject for encircling and edging field trials, with tests conducted in rectangular, trapezoidal, and irregular quadrilateral rice fields. The results show that, for rectangular plots, the full-field coverage rate of rice direct-seeding operations can reach 96.44%; for trapezoidal plots, the coverage rate is 95.47%; and for irregular quadrilateral fields, the coverage rate is 95.69%. These results are promising, indicating that the encircling and edging path planning based on the improved Reeds–Shepp curve can effectively increase the full-field coverage rate of unmanned agricultural machinery, improving work quality and meeting the needs of modernized, intelligent agricultural machinery operations. [ABSTRACT FROM AUTHOR]

In order to meet the agronomy demand for hybrid rice direct seeding, a novel precise pneumatic rice seed metering device was designed with groups of sucking holes plate, by which 3-4 seeds could be synchronously sucked and synchronously dropped into the paddy field. The plate was divided into five sections: seed sucking, seed clearing, seed carrying, seed dropping, and blank sections. The seeds were sucked in sucking section by the vacuum, carried and rotated to the dropping section with the plate, blown away in dropping section by the positive pressure air, and thrown into the dropping tube. The influences of the hole diameter, vacuum degree, and clear-up equipment on precision of metering device were discussed. Experiments were conducted to investigate the seeding precision and simulate the field emergence rates on the indoor seeding test-bed. The subjects were pregnant Indic hybrid Peizataifeng under two kinds of moisture content (23.43% and 26.07%). Other experiment conditions included the vacuum degree of 2.60 kPa, the rotation speed of seed sucking plate of 30 r/min, three sucking holes with a diameter of 1.6 mm, and the seed layer thickness of 25 mm. The seeding results showed that, in condition of no more than two seeds per hill, the emergence probabilities under the two moisture contents were 11.82% and 11.95%, respectively, and in condition of 3-4 seeds per hill, the results were 64.81% and 65.84%, respectively. With 2-5 seeds per hill, the results were 92.08% and 92.60%, respectively. If the emergence probability was 80%, under the two moisture contents, the no seed per hill probabilities were 1.33% and 0.80% respectively; the probabilities with 3-4 seeds per hill were 56.13% and 56.40% respectively; the probabilities with 5 or more seeds per hill were 10.67% and 10.13% respectively; the probabilities with 2-5 seeds per hill were 87.60% and 88.13% respectively. The results showed the simulated experiment was an efficient and economic method to assess the capability of pneumatic rice seed drilling metering device, and the precise pneumatic rice seed drilling metering device had a good prospect in practical application. [ABSTRACT FROM AUTHOR]