The multiple-seeding index was prop

The multiple-seeding index was proportional to the vacuum pressure, and the change trend of the missing-seeding index was opposite. A higher vacuum pressure generated a larger suction force in the nozzle. When the arm passed the seed pile, the tuber was sucked readily and less likely to detach from the nozzle, even the sucked tuber collided with the other tubers. As a result, the missing-seeding index was low. But, if the suction force was too large, the re-suck phenomenon was seriously. Similar to A, the C1 or the C3 was not the best choice for seeding. The qualified index increased first and then decreased with the rising of vacuum pressure, and reached the maximum value under the C2 condition. According to the results of ANOVA and range analysis, the optimum operating parameters were obtained as: the device rotating speed 30 r/min, the seeds height 25 cm and the vacuum pressure 10 kPa (A2B1C2). Under this condition, the multiple-seeding index was 1.1%, the missing-seeding index was 0.8% and the qualified index was 98.1%. The test procedure and results of mini-tuber test are shown in Table 5, and the results of ANOVA and range analysis are shown in Table 6. Table 6 shows that the effect intensity of factors on multiple-seeding index was C>A>B, on missing-seeding index A>C>B and on qualified index C>A>B. When the value of each factor was changed, the changes of the evaluation indexes were basically same to the conventional tuber test. The multiple-seeding index was 0.5%, the missing-seeding index was 0.6% and the qualified index was 98.9% under the conditions of rotating speed of the device 35 r/min, the seeds height 17 cm and the vacuum pressure 3.5 kPa (A2B1C2).