## 1 Introduction  
The total land area of paddy fields in China is 30 million \(\text{hm}^{2}\)[1], accounting for about 1/4 of the cultivated land in China [2]. Using a direct seeding machine for mechanized direct seeding of rice can effectively improve the degree of mechanization of rice production [3]. When the rice direct seeding machine is working, the seeding skateboard with larger grounding area is often pulled by the power head to flatten the surface in order to make the seeding mud surface smooth [4]. There is often a large amount of soil accumulation in front of the seeding skateboard due to the squeezing of the skateboard on the paddy field soil [5], which directly affects the operation efficiency, traction and adhesion performance, fuel consumption, and power consumption of the rice direct seeding machine, and also reduces the passability of the machine [6]. The serious choking of the mud also causes the seeds on the adjacent sides to be covered and affects the flatness of the paddy field [7]. The occurrence of the above problems is closely related to the contact between the planter skateboard and the paddy soil. Studying the ground pressure at the bottom of the skateboard is helpful to reduce the mud adhered to the surface of the skateboard and reduce the resistance of the skateboard during sliding [8]. The paddy soil used for transplanting and direct seeding has high water content, a fluid state, and remarkable rheological properties [9]. In order to accurately analyze the interaction process between seeding skateboard and paddy soil, it is necessary to study the rheological mechanical properties of paddy soil [10]. In order to understand the rheological properties of lacustrine soft soil at different stress levels, [PERSON] carried out a one-dimensional indoor consolidation creep experiment on soft soil in the Dongting Lake area. A rheological constitutive model under lateral confinement conditions was then constructed, and the analytical solution was obtained under one-dimensional consolidation conditions according to the fitted rheological constitutive model. The results indicated that soft soil in the Dongting Lake area has obvious nonlinear creep characteristics [11]. [PERSON] performed uniaxial compression experiments on soil samples and plotted rheological curves, thus establishing rheological models and rheological equations [12]. [PERSON] established an air-water-soil coupling model, used ANSYS/LS-DYNA to conduct a fluid-solid coupling simulation, and applied the rheological parameter research to the design and parameter optimization of a paddy soil boat tractor [13]. Domestic and foreign experts have carried out a lot of theoretical and experimental research regarding the ground pressure measurement technology. [PERSON] and others installed a self-made diaphragm ground pressure sensor at the bottom of a machine ploughing ship and measured the ground pressure at the bottom of the ship [14]. [PERSON] invented a device that can dynamically measure the distributed ground pressure from a crawler device of heavy equipment [15]. Moreover, [PERSON] designed a kind of ground pressure measuring device and a set of evaluation methods. The measuring device is embedded in the ground, then, when the car passes from above, the sensor and measuring device can detect the dynamic change of the ground pressure in the contact area between the tire and the ground, and analyze and evaluate the record [16]. In order to reduce the mud of the skateboard of the rice direct seeding machine, [PERSON] used a thin film sensor to measure and analyze the ground pressure between the skateboard and the soil in order to explore the force relationship between the skateboard and the soil [17]. This characteristic of paddy field soil strongly affects the operation performance and work efficiency of paddy field operation machinery.