Design and test of fluid and small-amount seed metering device for foxtail millet

Abstract：In order to solve the difficulties of sowing for foxtail millet and improve the low germination rate of millet after sowing in dry land of North China, we firstly studied the agricultural requirements of precision drill of millet without thinning out seedlings. We prepared a mixed suspension of foxtail millet using water and agricultural super absorbent polymers, because the agricultural super absorbent polymers can promote crop growth. We did some experiments to find suitable super absorbent polymers and the optimal proportion for mixed suspension according to the requirement of fluid seeding. At the same time we designed a kind of seed metering device by small-amount liquid for foxtail millet. This paper determined the number of rollers, dimension parameter and combination form of tube. It also expounded sucking seeds, delivering seeds and metering seeds of this seed metering device. This device consists of seed box, delivery pump, pump tube, three-way tube, long bent tube, end drainage tube and short bent tube. The function of delivery pump is providing power for the seed metering device, the function of three-way tube is dividing and combining the mixed suspension, the long bent tube or the short bent tube can improve the uniformity of seeding, and the end drainage tube can decrease every drop volume of mixed suspension to ensure that every drop has 2-3 seeds. Because the delivery pump has impulsive motion, we greatly reduced the impulsive motion of this device by using 6 rollers of .delivery pump and designing the structural style of tube, which has long bent tube, short bent tube, three-way tube and end drainage tube. The length of long bent tube is 100 mm, and the length of short bent tube is 74.4 mm. We also chose the material and diameter of tube. The material of tube is silica gel, which has the advantages of good elasticity and long service life. The diameter of pump tube, long bent tube, short bent tube and end drainage tube is 4.8, 4, 4 and 4 mm, respectively. Finally we designed and conducted the experiments of the uniformity and steadiness for mixed suspension of millet, and the variability coefficient of seed number was adopted. And we performed the performance tests with 4 indices adopted, including the percentage of damaged seeds, qualified rate of hill distance, qualified rate of seed number per hill, and rate of no seed hill for seed metering device in laboratory. We also carried out the field experiment of sowing with 3 indices including the qualified rate of hill distance, qualified rate of plant number per hill and seedling emergence rate for this device. The results showed that the suitable agricultural super absorbent polymer was Anxin for preparing the mixed suspension of foxtail millet, and the quality ratio of super absorbent polymers, grain of millet seed and water was 1.1 : 10 : 200 in mixed suspension; the variability coefficient of seed number was 9.8% in this mixed suspension, and was 9.7%-10.4% within 5 hours, and the seeds in mixed suspension had no obvious settlement. The percentage of damaged seeds was less than 0.01%, the qualified rate of hill distance was greater than 86%, the qualified rate of seed number per hill was greater than 75%, and the rate of no seed hill was less than 4% in laboratory test. The qualified rate of hill distance was greater than 77%, the qualified rate of plant number per hill was greater than 74%, and the seedling emergence rate was greater than 87% in field experiment of sowing. The results provide a theoretical reference for the design and analysis of seed metering device by small-amount liquid for small grain seeds.