Effects of harvesting stages and periods of seed storage on seed quality characteristics of three soybean (Glycine max (L) Merrill) Varieties

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Field and seed storage experiments were carried out between September 2012 and June 2013 to determine the most appropriate harvesting stage and period of storing soybean seeds, with minimal effects on seed quality characteristics. The field experiment was established using 3 x 3 factorial in Randomized Complete Block Design (RCBD) with three (3) replications. The seed storage experiment was set up using 3 x 3 x 3 factorial arrangement in Completely Randomized Design (CRD) with four replications. The field experiment was conducted at the Research fields of CSIR-Crops Research Institute at Fumesua, Kumasi Ghana (01⁰36'W; 06⁰43'N) with the treatment of harvesting soybean pods at physiological maturity, one and two weeks after physiological maturity. Physiological maturity was determined when 90% of the pods on the plant turned brown. Growth and yield characteristics were evaluated during seed production period. Germination percentage, seed vigour, 1000 seed weight, moisture content, fungal infection, protein and fat contents were assessed before storage, three and six months. The study revealed that soybean varieties harvested at physiological maturity recorded the highest seed yield, germination percentage, vigour and fat content while those harvested two weeks after physiological maturity had the lowest in the parameters listed. It was observed that temperature and relative humidity readings were high and fluctuated under ambient storage conditions. The 1000 seed weight and moisture content increased under ambient storage conditions. Further, irrespective of the variety, harvesting stage and storage period, a total number of thirteen fungi species were identified on the three soybean varieties before and during storage. These pathogenic fungi species contributed in reducing the quality of the seed particularly germinability and vigour at six months of seed storage. The results obtained indicated that for good yield and seed quality, soybean pods should be harvested at physiological maturity.
A thesis submitted to the school of Research and Graduate Studies, Kwame Nkrumah University of Science and Technology, in partial fulfilment of the requirement for the award of Master of Philosophy (M. phil. Seed Science and Technology). 2014