Seed moisture contents and potassium treatments affect the germination of soybean at low temperatures, and subsequent crop growth and yield

This study compared the effects of seed moisture contents, imbibitional temperatures and KNO3 treatment on germination, plant growth and yield of soybean [Glycine max (L.) Merr., cv 'Chaffey'] at different temperatures, in controlled environments and field experiments. Seed moisture contents, imbibitional temperatures and KNO3 had an effect on germination. Low temperature (5 deg C cf. 25 deg C) caused a reduction in maximum percent germination, and seedling growth up to 72 h after germination, when low (7-10 percent) moisture seeds were imbibed with water. No reduction was observed with high (18-25 percent) moisture seeds. When low moisture seeds were imbibed at warm temperatures (25 deg C) or imbibed with solutions of K salts (K+ was the effective ion) before exposure to cold, no reduction in germination occurred. Time to first seed germination and the spread of the time to germination in a population of seeds were effected by imbibitional temperature and/or temperature of germination but not by seed moisture contents or K treatment. The effect of seed treatments persisted to flowering of the adult plants in the field. At the flowering stage, both high seed moisture and K treatment had a positive effect on leaf area, number of branches per plant and number of nodules. Potassium treatment had a positive effect on seed yield only from low moisture seeds. Seed moisture content had a positive effect on seed yields from an early (September) sowing. Moreover high moisture (18 percent) seeds produced plants at the early sowing which flowered and matured earlier (139 cf. 147 DAS) than those from later sowings, and had the advantage of producing the biggest seed yields. In one sowing (October) low night temperatures at the end of flowering apparently caused reduction in seed yield even though the temperatures were warmer later. The low night temperatures had a marked effect on the proportion of pods containing seeds.