Effect of storage conditions on soybean seed quality produced by smallholder farmers within two districts of Gauteng, South Africa

Seed quality comprises of physical, physiological, and health attributes. Moreover, significant aspects of seed quality include seed viability and vigour. Maintaining good seed quality under sub-optimal storage conditions is one of the major challenges smallholder soybean farmers face. Hence, this study aimed to determine the effect of on-farm storage conditions on the seed quality of soybeans from smallholder farmers within the Gauteng Province, South Africa. The objectives of this study were to i) evaluate and compare the viability and vigour of farm-saved soybean seeds, and ii) evaluate the effect of seed moisture and simulated storage period on the rate of deterioration of the seeds. Farm-saved seed samples collected from the twenty-two smallholder farmers from two districts within the Gauteng Province showed significant variations in terms of seed moisture, viability, vigour [accelerated aging (Aa) and conductivity], and in the rate of deterioration. The seed moisture content ranged from 7.8-30.8 %. The majority of the farm-saved seed samples had a germination percentage significantly higher than 75 %, irrespective of the storage conditions. On the other hand, seeds subjected to Aa and to the controlled deterioration test resulted in less vigourous seedlings. Seeds that were subjected to 24 hr Aa had a significantly (p < 0.05) higher germination than those subjected to 72 hr Aa. The 72 hr Aa results verified the reduction of seed vigour as the storage period increased. A similar declining germination trend was observed on seeds subjected to deterioration tests under high moisture content levels. The study gives an indication of how the sub-optimal storage facilities used by smallholder soybean farmers affect seed quality. Based on the vigour tests, it can be assumed that storing seeds with high SMC under high relative humidity coupled together with high temperatures for prolonged periods tends to deteriorate the seeds rapidly and thus reduce seed vigour.