Influence of Seed Physical and Engineering Properties on the Design of Inclined Plate Seed Metering Mechanism

Abstract

The performance of seed metering mechanisms in planters is strongly influenced by the physical and engineering properties of seeds, which affect seed flow, singulation and placement uniformity. This study evaluated nine crop seeds—paddy, maize, groundnut, wheat, soybean, chickpea, linseed, mustard and finger millet—representing large, medium and small seed categories, with three varieties of each crop. The measured parameters included seed length, breadth and thickness, arithmetic and geometric mean diameters, sphericity, surface area, volume, thousand grain mass, moisture content, true density, bulk density, angle of repose and coefficient of static friction. The results showed considerable variability among crops and varieties. Groundnut recorded the greatest mean seed length (12.9 mm), followed by maize (9.25 mm) and paddy (8.08 mm), whereas finger millet had the smallest seed dimensions. Soybean showed relatively high sphericity, with a mean value of about 0.80, indicating a more rounded seed shape. Thousand grain mass differed markedly among crops, with groundnut showing the highest variability (standard deviation 59.87 g), while mustard and finger millet recorded the lowest mean values. Density, angle of repose and coefficient of friction also varied among crop groups, indicating differences in hopper filling, seed flow and interaction with planter components. Groundnut exhibited the lowest angle of repose, suggesting comparatively better flowability, while wheat showed greater variation in flow-related properties. The findings indicate that seed dimensions, shape, mass, density and frictional behaviour should be considered when selecting groove dimensions, hopper slope, material surfaces and metering-cell geometry for inclined plate seed metering mechanisms intended for multi-crop planting.