Experiment of sucking precision of sucking plate with group holes on rice pneumatic metering device

Abstract: Rice is the most important grain crop in China with a growing plant area year after year in recent decades. Direct seeding and transplant are the two main plant modes. Direct seeding by planter is getting popular in China, India, and other countries, with high efficacy and economy, as well as easy operation. Due to high capacity of tilling, generally three to four seeds are required for each hole in order to avoid a planter-like high empty hole rate. Meanwhile, the different variety and irregular shape of the seeds results in either excessive seeds in each hole, or empty holes when planters plant hybrid rice seeds that makes it quite difficult to meet requirements for current needs in the field. In order to realize precise farming, a unique precise pneumatic metering device was designed with a group sucking plate in seed metering device, by which three to four seeds can be sucked and dropped at the same time. The plate was divided into five parts, a seed sucking place, seed clearing place, seed carrying place, seed dropping place, and a blank place. The seeds were sucked by the vacuum and rotated to the dropping place by the plate. Different influences from the diameter of the hole, vacuum degree, and clear-up equipment on precision of metering devices have been discussed. In the experiment, the sucking plate rotating speed was 8 rpm and its diameter was 165mm. Rice varieties were Indic hybrid Peizataifeng whose moisture content (wet basis) was 11.6%~11.9%, and its 1000-grain was 22 g. Its overall dimension (length×width×thickness) was 8.94mm×2.30mm×1.94mm，and the 4×24 orthogonal experiments were conducted to investigate the suck characteristic of the group holes on the sucking plate under vacuum, diameter of the holes, and the seed-clearing device. The experimental equipment consisted of a pneumatic metering device with group holes, a U-shaped manometer, a positive and negative pressure air pipeline, a cut-off valve, and a vortex pump. The sucking probability of the group holes was the conditional probability of the single hole sucking probability, and the result showed that the sucking precision was affected by them. The order affecting the average sucking seeds per hill was diameter of the hole＞seed-clearing device＞vacuum; the order affecting the ≤2 sucked seeds per hill (lost sucking percentage) was vacuum＞diameter of the hole＞seed-clearing device; the order affecting the (3~4) sucked seeds per hill (qualified percentage) was diameter of the hole＞seed-clearing device＞vacuum; and the order affecting the ≥5 sucked seeds per hill (repetitive sucking percentage ) was diameter of the hole＞seed-clearing device＞vacuum. The optimal parameter combination was vacuum at 3.2kPa and diameter of the hole with 1.5mm and seed-clearing device; the ≤2 sucked seeds per hill, the (3~4) sucked seeds per hill and the ≥5 sucked seeds per hill were 8.27%, 81.87% and 9.86%. The result showed the sucking pate that had group holes performed well on sucking precision and has excellent application prospects.