| The effects of N and P fertilization, seeding date, and simulated frost treatment were evaluated with respect to the isoflavones, hydrolysable carbohydrate, sucrose, and seed coat color in Manitoba-grown soybeans in 2005 and 2006. Six levels and three placement methods for N and P in 2005 gave consistent results in terms of seed coat color, where no effects were observed. Hydrolysable carbohydrate levels were not improved by applied fertilizers. The use of P did not increase levels of isoflavones, though there did appear to be improvements in the isoflavones at low level N application or with applied Rhizobium inoculant. The effect of seeding date on these quality attributes was dependent on the variety and location. But it is hard to detect color difference due to the change of seeding date by human eyes. The frost treatment (1h/8h) did not affect mature seeds (95% brown). Seed discoloration at the earlier maturity stages (5% and 95% yellow) was greater with longer exposure to frost. Overall, the influence of these agronomic practices was minimal and inconsistent or varied among cultivars, locations, and years, although adverse effects of frost on color at early stages of maturity were clearly demonstrated. |
