###### Abstract
The capacitance method measures the application rate by the difference in the dielectric coefficient between material and air. However, it requires repeated calibration due to the limitation of the material characteristics and types in actual field operation. The measurement accuracy is also difficult to guarantee [21; 22]. The weighing method is used to calculate the real-time and cumulative application rate by measuring the material weight in real-time. The weighing method is simple in principle and intuitive in measurement. The difficulty lies in overcoming the vibration interference from the machine during field operation and reliably extracting the weighing signal [23]. These methods have been proven to effectively measure the cumulative application rate over a certain period, but the feasibility of closed-loop control for the application rate of wheat fertilizing and seeding operations has not been reported. For wheat seeding and fertilizing applications, an applicator with fluted rollers is widely used in the seed-fertilized drill machine, due to its reliability and stability, and is especially suitable for the seeding of non-single seeds or granular material, such as solid granular fertilizer and wheat [24; 25]. The application rate of seeding and fertilizing applicators with fluted rollers is dependent on the material density, material filling coefficient, driving layer characteristic coefficient, wear and tear (brush damage, gap change between brush and fluted rollers), material adhesion, and clogging [26]. Further, the relationship model between the mass flow rate and the rotation speed changes over time due to these factors. Consequently, the precision of wheat seeding and the fertilizing application rate is impacted negatively if calibration is not carried out frequently. The calibration relationship model between the fluted-roller mass flow rate and rotation speed is relatively stable over a short period because there are no noticeable deformations or damage in the brush, which is installed inside the fluted-rollers. Hence, it is more economical and feasible to improve the accuracy of the application rate by calibrating the open-closed relationship between the mass flow rate and rotation speed in a timely manner, based on test results during the operation over a set period. Due to the lack of reliable, high-precision, and real-time application rate detection methods and devices, it is difficult to establish a closed-loop control system to control the application rate in actual production. The accuracy of the control system for controlling the application rate depends on the correctness of the control model. The control model commonly used at present is based on the calibration relationship model of the mass flow rate and the rotation speed of the fluted-roller driving shaft. The parameters of the calibration relationship model will change with the increase of working time and the change of working conditions, which affect the control performance of the control system. The aim of this paper is to establish a method which can self-calibrate the parameters of the relationship model according to the measured data while working to dynamically adjust the parameters of the control model and maintain the control accuracy of the control system that is running in a closed-loop. In this paper, the application rate measurement device [27], which was based on the weighing principle (and previously designed by the author's team), was used to measure the relationship model between the dynamic cumulative application rate and the dynamic cumulative rotation cycles in a certain period of time. Furthermore, the ratio coefficient between the mass flow rate and rotation speed can be obtained using the established relationship model.