Design and experiments on soil spreading devices of plastic cell-tray type planter for raising super hybrid rice seedlings

Two types of soil spreading devices were designed for the planter used in raising super hybrid rice seedlings in the plastic cell-tray, as well as the soil spreading device with the cylinder of 4-spiral-groove and the belt type of soil-spreading device were designed. Under the productivity of 450 trays/h (the corresponding speed of cell-tray is 0.075 m/s), the experiments were carried out with different soil water contents, soil granule sizes and soil spreading gaps. Results show the soil spreading gap of 3 and 1mm are appropriated for the soil spreading device with the cylinder of 4-spiral-groove while spreading soil granules after passing through 5 and 3 mm sieve pore, respectively. For the belt type of soil-spreading device, the soil spreading gaps are 6-7 and 5 mm, respectively. Both soil spreading devices quality and uniformity performed better for wet small soil granules than dry large soil granules. It is more important that the working condition can be improved while spreading wet soil granules. Soil spreading devices can meet soil spreading requirements of super hybrid rice seedlings raised in plastic cell-tray. However, the belt type of soil-spreading device show more problems in the experiments. The uniformity performance of spreading soil can be evaluated by using the variance analysis and the multiple comparisons test.