Standardization of Optimum Grading Sieve Size for Seed Processing in Black Gram [Vigna mungo (L.) Hepper] Varieties

Abstract

Background: The seeds harvested from the field may not be homogenous in seed size, physical purity and viability in Black gram. Seeds are to be cleaned and graded using seed processing machineries to maintain uniformity of a seed lot. Every variety is having its individuality in seed size. Hence, the common recommendation of 2.8 mm sieve size recommended by Indian Minimum Seed Certification Standards (IMSCS) for grading black gram seeds may not be suitable to recover a maximum quality seeds in all varieties while processing. The present study was carried out to identify a suitable grading sieve size for newly released black gram varieties for getting good quality seeds with better seed recovery during processing. Methods: The study was conducted at Seed Technology Research Unit, Pandit Jawaharlal Nehru College of Agriculture and Research Institute, Karaikal during the year 2020-2023. The experiment was laid out in completely randomized design with four replications. Four newly released black gram varieties viz., ADT 6, VBN 8, VBN 10 and VBN 11 were taken for the study. Specified quantities of unprocessed seeds have been sieved using slotted sieves of three sizes above (3.4 mm, 3.2 mm and 3.0 mm) and two sizes below (2.7 mm and 2.5 mm) the recommended sieve size of 2.8 mm for black gram varieties as per the IMSCS. The seeds retained over each sieves were collected separately and tested for seed quality parameters. Result: The results revealed that the seed recovery percent increased with decrease in sieve size while the seed quality parameters found higher with increase in sieve size.The sieve size of 2.7 mm (slotted) registered the maximum cumulative seed recovery of 87% and 89.9%, respectively in Black gram seeds of cv. ADT 6 and VBN 10 along with required seed standards. However, seeds retained from the sieve size of 3.0 mm (slotted) registered the maximum cumulative seed recovery of 91.2% and 87.5%, respectively in VBN 8 and VBN 11 with requisite seed germination and physical purity as per the IMSCS (75% and 98%). Hence, it is suggested that the sieve size of 2.7 mm may be considered as grading sieve size for seed processing in Black gram seeds of cv. ADT 6 and VBN 10 and 3.0 mm may be used as grading screen (Bottom screen) for VBN 8 and VBN 11 for getting good quality seeds with higher seed germination, physical purity and pure live seeds.