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The mechanized seeding operation is an important part in modern agricultural production, and the net operating time utilization rate of the seeder is an important indicator to impact the efficiency of seeder unit. According to machinery unit application principle, the new term of seasonal net time utilization rate was determined in this paper, each consumed time items of seeder unit was distinguished and relevant mathematic models were established based on mechanized seeding practice and sufficient survey, such as net operating time, turning time and time of adding fertilizer and seeds and so on. Based on this, three mathematical models of net operating time utilization rate of seeding machinery units were established according to different adding fertilizer and seed ways. The experiment scheme was designed, which uses the method of multi-point synchronous tracking measurement to test the time items in the seeding process without disturbing the normal seeding process. Data of each time items of 4 typical seeding machinery units were obtained during the experiments. The statistic principle of 3ᓂ was used to distinguish and eliminate invalid experiment data. Based on the models established and effective tested data, Matlab 2012b was used to analysis the net operating time utilization rate of the 4 seeding machinery units changing with plot length and area under 3 different ways to add fertilizer and seed, the test results were expressed using Sigmaplot 12.5 software, and th quantitative correspondence between the different typical seeding machinery units and suitable operating plot area and length under the aimed net operating time utilization rate were determined. The results showed that when the aimed net operating time utilization rate of seeding machinery units is greater than 0.6, the John Deere 7 830 unit is suitable for the plots with areas no less than 6 hm² and the plot length is 1 200-1 400 m. The Valtra 171 unit is suitable for the plots with area no less than 6 hm² and the plot length is 1 000-1 200 m. The suitable plots for Changfa 504 unit are that area is no less than 1 hm²and the plot length is 500-1 500 m. The plots with area no less than 0.3 hm² and the plot length is 200-1 500 m are suitable for Huanghai 254 unit. The results can provide scientific accordance to select seeding machinery units for different plots. [ABSTRACT FROM AUTHOR]

It is theoretical basis for harvest machinery selection to discuss technology productivity changing with plot conditions, which are plot area, length, width and so on under the condition of land managing scales over the wide range. Harvesting operation is one of the key processes of grain production, and choosing the appropriate harvesting machine is a vital step to reap the grain with larger technology productivity. A lot of researches on agricultural mechanization selection have been done by both domestic and foreign experts. It has been found that there are existing methods for agricultural machine selection such as fuzzy clustering comprehensive evaluation method, linear programming, and mixed integer linear programming. In these methods, the economic performance of the agricultural machinery unit is the objective considered in most cases. But the technical performances of agricultural machinery units, such as the practical productivity, are usually neglected. Plot conditions, including plot area, length, width, and distance between plots, are not considered in the methods, but they are important factors influencing the technology productivity of agricultural machineries. At the same time, it has also been found that the power of most agricultural machineries does not match the plot conditions in the practice of agricultural production. In this paper, the mathematic models calculating every kind of time consumption item during combined operation, including working time, turning time, preparation time before unloading, unloading time, preparation time after unloading and transferring time between plots, were established. On the basis of that, the mathematic models for calculating the combines’ technology productivity under the condition of different unloading ways were also set up. These mathematic models contain the variables such as plot area, length, width and distance between plots, and reveal the regularities of technology productivities changing with plot conditions. Experiment was designed according to the method of tracing the practical operating process. Taking 8 kinds of typical combines for harvesting soybean as experiment objectives, the values of all kinds of time consumption items were tested under the condition of fixed distance during the process of normal harvesting operation after enough experiments were executed. All the data of time consumption items were checked using the normal distribution models and the error data were removed according to the 3-Sigma principle. The mathematic models of time consumption items and combine technology productivity established were proved to be correct by the experiments and the actual operating status. According to the models and tested data, the technology productivities of 8 kinds of combine harvesters changing with plot conditions were calculated after the MATLAB program was designed and executed. Curve groups of technology productivity of each kind of combine changing with plot conditions were drew out using the EXCEL. Thus, the quantitative regularity of technology productivity of combine changing with plot conditions was revealed. According to the regularity, the technology productivity became larger as the value of plot area and length became bigger, but the changing velocity of technology productivity became slow after a specific values of plot area and length. The technology productivity of combine with the header width of 2-3 m was higher when the plot area was more than 3 hm2 and the length was more than 400 m. For the combines with the header width of 4-5 m, the technology productivity was higher when the plot area was more than 5 hm2 and the length was more than 600 m. The technology productivity of combine with the header width more than 7 m was higher when the plot area was more than 7 hm2 and the length was more than 800 m. The results of the paper can provide the direct theoretical guidance for practical combine selection under the status of land managing scale with large range, and they are also the improvement and supplement for the theory of agricultural machinery selection. [ABSTRACT FROM AUTHOR]