Potato is an annual plant with the scientific name of Solanum tuberosum L. from the tomato genus (Solanaceae) and autotetraploid with 48 chromosomes. Potatoes are grown to use its underground tuber. According to the crop statistics of 1397-98, the total area under potato cultivation in Iran is slightly more than 146 thousand hectares. About 5 million tons of potatoes have been harvested this year, with an average yield of about 36.5 tons per hectare, making the country the 13th largest producer in the world. Potatoes rank fourth in terms of production volume among various agricultural products after wheat, rice and corn. Potato planters in Iran, plant them at a constant distance regardless of the potato size which leads to heterogeneous distribution of stems at the field level. The main purpose of the present study was to design, manufacture and eva‎luate of a special belt metering potato. Belt planters use a group of belts to receive, deliver and plant potatoes. In this type of planter, the potatoes fell from the hopper on the middle planting belts of the machine. Return belts move in the opposite direction and guide the extra potatoes to the beginning of the path to be used for reloading by the middle belts. Part of this study is about measuring the dimensions of potatoes by digital caliper and obtaining the geometric mean diameter, sphericity and shape coefficient of potatoes. In this research, appropriate design of all the components required for the belt-type potato metering device was carried out followed by detailed drawings on CATIA software. The belt-type metering device was developed using the facilities available in the biosystems engineering workshop of Isfahan University of Technology. The eva‎luation was performed in the laboratory with the use of a test rig. The forward speed of the test rig and belt-type metering device were adjusted by the inverter. A factorial experiment conducted in a completely randomized design with 3 replicates to investigate the effect of three forward speeds of planting belts (3, 4.5 and 6 km/h), three forward speeds of test rig (3, 4.5 and 6 km/h), three potato sizes (25-35, 35-45 and 45-55 mm) and two potato shapes (spherical and oval) on the mean planting distance, standard deviation, multiple planting index, miss and quality feed indices and the accuracy. In this research distance between two consecutive potatoes on the planting line were measured with a metal tape meter. Data analysis was performed using SAS 9.4 software. Results showed that the mean seed spacing, standard deviation, multiple planting index, miss and quality feed indices were significantly depend on the forward speeds of the belt metering device and the test rig, also on the potato sizes and shapes. Mean seed spacing and miss index were found to increase with increase in forward speed of the test rig while feeding quality and multiple planting index decreased. The highest feeding quality index of 81.85% was observed in the forward speed of 3 km/hr.

مهرنوش جعفري، علي اسحق‌بيگي

مرتضي صادقي، آقافخر ميرلوحي