Abstract:In order to adapt simplification precision hilldrop seeding for conventional rice and simplify the seedmetering device, a unique Ushaped cavity type precision hilldrop seedmetering device for rice was designed. Based on the mechanical characteristics of rice seeds and its agronomy requirements of hilldrop seeding, a cavity type seeding plate was put forward, which characterized with seeddropping orifice and seedfilling orifice connected by the cavity, the mechanical models of the process of seed filling and dropping were constructed, and the main structural parameters of the seeding plate were determined. The seeding objects was “Huanghuazhan” (conventional rice), experimental studies were respectively carried out on the effects of the number, length, width and inclination of the seedfilling orifice and seeddropping angle on the seeding performance of precision and hilldrop of the seedmetering device by means of highspeed camera and JPS-12 type seedmetering device performance test bench. Highspeed camera test results indicated that the precision seeding performance of the seedmetering device was better when the number, length, width and inclination of the seedfilling orifice were 20, 10.6mm, 7.6mm and 0 degree, respectively. Correspondingly, the missseeding rate (less than 3 seeds per hole), qualified rate (3~8 seeds per hole), reseeding rate (more than 8 seeds per hole) and seed damage rate were 0.40%, 94.00%, 5.60% and 0.13%, respectively. JPS-12 type seedmetering device performance bench test results indicated that the seeddropping angle very significantly affected the average value and qualified rate of hole diameter, and significantly affected the variation coefficient of hole distance. The suitable seeddropping angle of seedmetering device was 28°~33°. Under the above range of seeddropping angle, all the average hole diameter were not more than 27.14mm, all the qualified rate of hole diameter were not less than 96.67%, all the average hole distances were about 140mm, and all the variation coefficient of hole distance were not more than 7.80%. The results of field experiment showed that the qualified rate, missseeding rate and reseeding rate were 90.28%, 0.83% and 8.89%, respectively. And the average hole diameter of 46.71mm, qualified rate of hole diameter of 71.67%, average hole distance of 137.21mm and variation coefficient of hole distance of 12.64% were found in the field experiment. All the sowing performance satisfied the general precision direct hilldrop seeding requirement of conventional rice in field. The research result provided a theoretical reference for the simplification design of the mechanical seedmetering device.