The seed size was determined by length (l), width (w), and thickness (t). Maize seed size is an essential parameter in designing the cell size on the seed metering mechanism. Vernier caliper was used to measure the axial and lateral dimensions of the seeds. Ten seeds were randomly selected, measuring the dimensions. The mean values have been estimated, and this value was used to design the metering mechanism. It was calculated by using the formula specified by (Mohensin 1970). It is shown in Fig. 2.

Where l = mean length of the seed, mm w = mean width of seed, mm t = mean thickness of seed, mm

The geometric mean seed diameter was measured with seed dimensions. The geometric diameter was determined using the following relation.

Geometric mean diameter, D_g = (l w t )^1/3, mm

Sphericity is known as the ratio of the sphere’s diameter having the same volume as that of the particle and diameter of the smallest circumscribing sphere, or the largest particle diameter generally. This parameter indicates the shape character of maize seeds relative to the same volume of a sphere. The dimensions of 10 maize seeds at random were measured using digital vernier caliper to calculate the seed sphericity.  Sphericity, φ= Volume of the particle  Volume of the circumscribed sphere 

An electronic weighing balance with a precision of 0.01 g was used to determine the weight of thousand seeds. A sample of 100 seeds was randomly selected and weighed to determine the mean weight of 1000 seeds. To minimize the errors, the procedure was replicated five times.

Angle of repose is an important parameter that helps in the design of the hopper of the planter. A box with a circular base was mounted in the funnel, and three adjustable screws were used to hold the platform horizontally. It was filled with maize seeds. The seed gate on the underside of the funnel was removed so that a conical heap was formed on the surface. Heap height and diameter were measured. The angle of repose was calculated using the following equation. It is shown in Fig. 3.  Angle of repose, θ=tan−1(2hd)

Where h = height of the cone formed, cm d = diameter of the base of cone-formed, cm

A measuring cylinder was used to calculate the bulk density. A 1000 cc capacity measuring cylinder was taken, and its weight was taken as W₁. The seeds were filled up to the 1000 cc limit, and the cylinder was gently tapped, and weight was taking as w₂. The difference between w₂ and W₁ was considered seed weight. Five replications were taken to minimize the error. Bulk density was calculated by using the following formula.  Bulk density (kgm−3)= Weight of seed, kg Volume of cylinder, cm3

The porosity is the fraction of the space in the bulk seeds which is not occupied by the seeds (Mohensenin, 1986). The porosity of the samples was computed from the bulk and true densities using the following equation:  Porosity, ε(1−ρbρt)×100

Where, ρ_b = bulk density, kg m^-3 ρ_t = true density, kg m^-3

The total area covered around the seed is the surface area of the maize seed. It can be given by the following formula:  Surface area, S=πDg2

Where D_g = geometric mean diameter, mm

Coefficient of static friction can be expressed in terms of the degree of the seed resistance to flow on a given surface. It is an important property to determine the angle at which the hopper development has to be done so that the constant flow of the seeds from the hopper to the seedbox is achieved. Coefficient of static friction is measured using the inclined plane method. The seeds were filled in a square box having dimensions 60 × 65 × 65 mm, and the box was placed on the surface to measure the static coefficient of friction, then the surface on which the box lies was raised with a screw device. The angle at which the box begins to slide was noted from the graduated scale on the apparatus. The coefficient of static friction was calculated as the tangent of an angle of inclination and is given by the following equation. It is shown in Fig. 4.

Coefficient of static friction, µ = tan α

Where α = angle of inclination.

Major, intermediate and minor dimensions of the three maize verities are Rasi-3033, NMH-589, and KMH-2589 are given in the table 1. For Rasi-3033 the seed length varied from 10.42 – 11.60 mm, intermediate dimensions are in the range of 7.11 – 8.63 mm, and the minor dimensions are 4.13-4.94, having mean values of 11.00, 7.75, and 4.58 mm respectively. NMH-589 seed having the length, width, thickness is varied from 9.87 – 10.59 mm, 7.92 – 8.99 mm, and 4.91−5.32 mm respectively. KMH-2589 seed variety having a length range from 7.97 – 8.99 mm, width varies from 6.29 – 7.01 mm, and thickness is about 4.22 – 5.55 mm. The geometric mean diameter of all three varieties is 5.91-7.061. the sphericity of all the seed varieties 0.65 – 0.78. These observations show that the maize seed was oblong in shape.

Table 2 shows the test weights of the various maize seed varieties under investigation. Due to differences in maize seed size, there was variation in the test weight of different varieties. Rasi-3033, NMH-589, and KMH-2589 maize seeds have an average hundred grain weight of 26.99, 21.02 and 24.0 g, respectively. As a result, the test weight varies very little. The seed rate per hectare is estimated using the thousand kernel weight of maize seeds as a main factor. The average weight was between 210 to 260 g.

The average values of angle of repose for three maize seed varieties were 29.49⁰, 30.20^0, and 29.54⁰. Angle of repose is used to determine the slope of the seed hopper sidewalls to facilitate the free flow of maize seeds.

The bulk density of all four varieties were shown in table 2. The bulk density of all three maize seed varieties ranged from 710 to 746.4 kg m^-3. The variation in bulk density between the varieties was due to the difference in the individual weight of individual grain and particle distribution i.e, variation in the size among the variety.

The values for the coefficient of static friction for Rasi-3033, NMH-589 and KMH-2589 maize seed varieties found 0.60, 0.59 and 0.55 respectively.