Influence of seed size, storage and priming on germination, growth and yield of soybean (Glycine max (L) Merrill)

Experiment was conducted at the Physiology Laboratory of the department of Crop Science, University of Ghana and on the field of the Ghana Atomic Energy Commission, Accra, to evaluate the influence of seed size, storage and priming on seed germination, growth, and yield of soybean. Germination tests were performed at the Physiology laboratory of the University of Ghana at two monthly intervals over 10 months using two priming agents, Vitazyme (at concentrations of 3, 5 and 7 %) and Calcium chloride (at concentrations of 0.5, 1 and 1.5 %) and hydro-priming. The duration of priming was six and 12 hours. Dry unprimed soybean seeds served as control. Treatments were laid in a completely randomised design with four replications. Field experiments were also conducted during Major (April-July, 2023) and Minor (July-November, 2023) planting seasons using soybean seeds graded into three sizes (small, mixed seeds, and large) and a priming agent (most promising priming agent from the Laboratory experiments). The field treatments for the Major planting season consisted of seed size (small, mixed seed, and large) and priming with CaCl2 at a concentration of (0.5 and 1 %). Treatments were laid in a split-plot design with four replications. Seed sizes were assigned to the main plot, while priming agents were assigned to the sub-plots. The seeds used in the major planting season had been stored for five months after seed harvest. The Minor season experiment had similar treatments and experimental design as the Major season experiment, except that Vitazyme at 5% concentration and CaCl2 at 0.5% concentration were used as the priming agents in the Minor season experiment, and seeds used for planting had been stored for seven months after seed harvest. Results from the laboratory experiments indicated that seed quality indicators, like germination and vigour, declined with prolonged storage. Percentage germination ranged from 57% with seeds stored for 11 months after seed harvest to 90% with seeds stored for seven months after seed harvest. Percentage germination for primed seeds varied significantly, ranging from 56% with 1.5% CaCl2 concentration to 85% with the unprimed control. Among the primed seeds, percentage germination ranged from 56% with 1.5% CaCl2 concentration to 78% with 0.5% CaCl2 concentration. The most vigorous seedlings, with a vigour index of 1290, were obtained from seeds primed with CaCl2 at a concentration of 0.5%, while a concentration of 1.5% CaCl2 produced the least vigorous seedlings, with a vigour index of 656. A priming duration of 12 hours led to a three percent reduction in percentage germination compared to six hours priming duration. During the Major planting season, the percentage emergence for primed seeds varied from 15% with CaCl2 at 1% concentration to 75% with dry, unprimed seeds. Priming interacted with seed size to significantly improve the weight of 1000 seeds, ranging from 115 g for large seeds primed with CaCl2 at 1% concentration to 155 g for large seeds that were hydro-primed. The Chlorophyll content varied from 15 μ/m2 in the unprimed control to 21 μ/m2 in seeds treated with CaCl2 at 0.5% concentration. Grain yield ranged from 1.27 to 2.66 Mt/ha for small seeds primed with CaCl2 at 0.5% concentration and mixed seed sizes primed with CaCl2 at 0.5% concentration, respectively. In the Minor planting season, the percentage of seed emergence varied from 66% with seeds primed with 5% Vitazyme concentration to 98% with unprimed seeds. Leaf Area ranged from 20.4 m2 to 30.1 m2 for seeds primed with 0.5% CaCl2 concentration and unprimed respectively. Priming significantly increased the weight of 1000 seeds, with unprimed seeds weighing 515 g and Vitazyme-primed seeds weighing 765 g. Grain yield ranged from 2.33 Mt/ha with small seed size primed with CaCl2 at 0.5% concentration to 3.44 Mt/ha with mixed seed size primed with a 5% Vitazyme concentration. The study suggests that soybean seeds should not be stored beyond seven months after seed harvest to achieve excellent germination. The studies also suggest that soybean seeds of any size could be used for planting, provided they are of good quality.