Abstract

                                In an attempt to find out a suitable sieve size and machine speed for grading sunflower seeds in a two screen cleaner cum grader, performance of various sieve sizes (round perforated) and machine speed on seed quality was studied. Decrease in sieve aperture size from 5.5 to 4.5 mm and increase in machine speed from 150 to 225 rpm improved the recovery percentage. However, the physical attributes such as seed length, width, and weight decreased with the decrease in sieve aperture size and increase in grading speed. Germination was higher in seeds retained on 5.5 mm sieve (98.0%) and lower in seeds passed through 4.5 mm sieve (86.0%). The seedling growth and vigour parameters also showed a similar trend. Germination, seedling growth and vigour index of seeds graded at a midrange speed of 175.to 200 rpm were more compared to the extreme speeds of 150 and 225 rpm. For maximum recovery and better sowing quality, grading sunflower seeds using 4.5 mm sieve at a speed range of 175 to 200 rpm was found to be optimum..

Key words : Seed grading, seed recovery, seed quality, sieve size, sunflower.