Determination of seed moisture content in small-seeded pasture legumes

Abstract

An improved technique for the determination of seed moisture content in small-seeded annual legumes is described. Changes in weight of permeable and impermeable seed of Medicago truncatula, M. polymorpha and Trifolium subterraneurn, which were either left intact or cut in half, were measured in air-ovens at 105 and 130¦C. Drying intact seeds for 1 h at 130¦C, as specified by the International Seed Testing Association, seriously underestimated moisture content in most seed samples. Seeds dried to approximately constant weight at 130¦C appeared to overestimate moisture contents by about 1%, presumably because of volatilisation losses of material other than unbound water. At 105¦C, halved seeds lost weight rapidly during the first day then slightly gained weight for several days before resuming a gradual weight loss. Drying intact seeds of M. truncatula and T. subterraneurn at 105¦C for 2 days gave seed moisture contents similar to those obtained from halved seeds. Intact impermeable seeds of M. polymorpha were very much slower than those of the other species to lose weight. taking 14 days to approach an apparent moisture content close to that of halved seeds. Drying halved seeds for 24 h at 105¦C appears the most reliable technique.