Grading of Seeds

Grading of Seeds 

in a seeder, the division of seeds, according to size, into groups corresponding to the sizes of the compartments in the seeding mechanism.

Seed is sorted so that seeds can be sown one by one or in sets of a predetermined number, decreasing waste of the sowing material and cutting down sharply on the labor needed to tend the plantings. Corn, sugar beet, cotton, and other crop seeds are graded after preliminary machine-cleaning. Agricultural grading machines or seed cleaners with the necessary gratings are used for the process.

Large-scale seed grading was first used in the USSR with corn after construction in 1956– of grading plants, which supply seeds (packed according to grade in sacks) to kolkhozes and sovkhozes. Corn kernels fall into six grades, according to thickness and width (see Table 1).

Table 1
Grade number	Size of seeds (mm)
	Width	Thickness
1…………	9.0–10.5 (11.0)	3.75–5.5
2…………	8.0–9.0	3.75–5.25
3…………	7.0–8.0	3.75–5.0
4…………	6.5–7.0	3.75–4.75
5…………	8.0–10.5 (11.0)	5.25–7.0
6…………	6.5–8.0	4.75–7.0

Sugar beet seeds are graded (using screens with round open-ings) into two groups (diameter, 4.5–5.5 and 3.5–4.5 mm). Cot-ton seeds are graded in cotton ginning plants, according towidth, thickness, and length, into two groups, after first remov-ing the linters from their surface.