Optimization of design and operational parameters of a soil-dispensing machine for preparing seedling tray

The conventional method of soil filling into nursery trays before seeding is known to be the most inexpensive approach prior to planting vegetables. However, this activity is very labourious and time-consuming if the operation is meant for high volume seeding. This study is done to develop soil-dispensing machine, evaluate its performance and to compare with traditional practice of soil filling into the nursery tray. The optimization of each parameter is also evaluated to obtain the exact volume of soil to fill the nursery tray to the fullest. A low-cost soil dispensing machine is developed in MARDI and it is using locally materials available in the market. The structure of the machine is fabricated using mild-steel and stainless-steel at the less cost. The machine consists of a conveyor, nursery tray holder, soil dispenser, scrapper, soil compactor, wiper motors, gears, microcontroller and sensors. There are three factors with two levels involve in this test; hopper angle, conveyor speed and auger speed. The hopper angles are evaluated at 45° and 65° while conveyor speeds are tested at 19 cm/s and 21 cm/s. The minimum and maximum speed of auger selected is 3.5 cm/s and 4.5 cm/s, respectively. Manual filling of soil into seedling tray was compared with filling soil using semi-automatic operated soil-dispenser. The results indicated that the model is significant with p-value <0.0001. Conveyor speed, auger speed and hopper angle were significant on the volume of soil dispensed with both speeds shows a p-value <0.0001, while hopper angle shows p-value equal to 0.00112. The combination of both speeds greatly affected the response with p-value <0.0001. There is no interaction between each speed and the hopper angle. From the optimization analysis, the operating conveyor speed, auger speed and angle of hopper should be set at 19.0 cm/s, 4.5 cm/s and 65° to discharge 2912 cm³ soil. In order to dispense 1190 cm³ of soil, conveyor speed, auger speed and hopper angle should be set at 21 cm/s, 4.3 cm/s and 50°. The result indicated that the machine can complete the seeding and soil filling process within 1 min per tray, while manual process took five minutes to complete the whole seeding process.