Influence of variety endosperm type and seed moisture content on threshability and mechanical damage of sorghum seeds

W.M. Muiru1, P.L. Fabiola1, D. Mbuge2, L. M’Ragwa3, S.L. Kimaru1*

1Department of Plant Science and Crop Protection, University of Nairobi, P.O Box 30197, Nairobi, Kenya
2Department of Environmental and Biosystems Engineering, P.O Box 30197, Nairobi, Kenya
3Kenya Agricultural and Livestock Research Organization (KALRO), Kenya

(Manuscript received 13 April 2020; accepted for publication 3 June 2020)

Abstract. Sorghum is an important cereal crop and it is native in African tropical areas. It is a globally cultivated crop and the fifth most important cereal after maize, rice, wheat and barley. The objective of this study was to determine the effects of endosperm type, seed moisture content and threshing methods on percentage threshability and mechanical damage of sorghum seeds. Two varieties of sorghum (Kari-mtama 1 and Seredo) were grown in two diverse locations, Kiboko and Katumani. Variety Kari-mtama1 has hard (vitreous) endosperm while the other variety Seredo has soft (non-vitreous) endosperm. After harvesting, sorghum panicles were dried in the sun and oven. The panicles were threshed separately for each drying method at two moisture levels, namely 18-20% and 13-14%. The three threshing methods used included beating with wooden stick in tied sack, using wooden mortar and pestle as well as using threshing machine. The results showed that the vitreous endosperm variety had significantly high percentage threshability and significantly low mechanical damage than non-vitreous endosperm variety under both drying methods. There was a significant (p≤0.05) increase in threshability and decrease in mechanical damage when the seeds were threshed at 13-14% moisture content compared to 18-20%. For better seed quality, threshing machine is the best method to be used to avoid mechanical damage and seed quality deterioration. Drying methods used to dry seed panicles before threshing had no effects on threshability and mechanical damage. This implies that sorghum panicles can be dried either in the sun or oven without affecting threshability and mechanical damage at the two moisture levels and by using the three threshing methods.