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.%针对新型超级稻精量穴盘育秧播种机对穴盘穴孔排覆土的要求,设计了2种排土器,双向4螺旋外槽轮式排土器和带式排土器.在保证每小时450盘(相应的秧盘输送速度为0.075 m/s)的生产率情况下,做了不同土壤含水率、不同土壤颗粒尺寸、不同排土间隙对排士效果影响的试验研究.结果表明,对于双向4螺旋外槽轮式排土器,播过5 mm筛和过3 mm筛的土壤颗粒时,排土间隙分别为3和1 mm为宜；对于带式排土器则分别为6～7和5mm左右为宜.2种排土器,均是播过3 mm筛的小颗粒土壤的播土均匀性和播土质量要好于播过5mm筛的大颗粒土壤.对于相同颗粒尺寸的土壤,高含水率(13％左右,湿基)的土壤播土质量要好于低含水率(5.72％,湿基)的播土质量,更主要的是可以改善工作环境.在保证不增加高湿土壤处理难度的前提下,建议采用小颗粒湿土进行播土作业.所设计的2种排土器均能满足超级稻穴盘育秧的播土要求,但需要注意对带式排土器的张紧平衡调节,且要避免大于排土间隙的土壤颗粒进入带式排土器中.排土器的播土均匀性可以采用播土高度均值的多重比较检验方法进行评价.
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