Using a registered seed treatment is recommended as soybean is susceptible to several seed and seedling pathogens and insects. The most current Saskatchewan Ministry of Agriculture publication Guide to Crop Protection lists commercial products appropriate for soybean.
Recommended seeding dates are from May 10 to 25, or when the average soil temperature has warmed to at least 10 °C. Seeding into cold soils may result in poor germination, increased incidence of diseases, and poor plant stands. Soybean seedlings can generally tolerate -2C frost. Delaying the seeding date can result in lower plant height, pod counts, and lower yields.
The target plant density for solid seeding soybean is 180,000 - 230,000 plants per acre, or four to five plants per square foot (44 to 57 plants per square metre). This equates to a seeding rate of approximately 70 to 147 pounds per acre depending on seed size.
Exceeding these rates can lead to drought stress in dry years or lodging in wet years. Soybeans have the ability to branch out and compensate for reduced stands. However, Ontario experience indicates a loss of 24 per cent in yield if plant stands are less than half of optimum height.
Soybeans can be sown using an airseeder or row crop planter (with proper plates). If using a row crop planter, the recommended optimum plant stand is 160,000 to 190,000 plants per acre. Row spacing should not be more than 22 inches. The following equation may be used to calculate seeding rate:
Seeding Rate (lbs/acre) = Desired Plant Population/ft2 x (1,000 kernel weight) / *% Expected Seed Survival x 10
Example: Variety 23-10RY soybean = 2600 seeds/lb
1000 seeds = approximately 174 g
Seeding Rate (lbs. /acre) = 4 x 174 g/95% x 10
Seeding Rate (lbs. /acre) = 73
The recommended soybean seeding depth ranges from 0.75 inches to 1.5 inches (1.9 cm to 3.81 cm). In loamy or clay soils seed in the shallow range, seed deeper in light textured soils so that the seeds remain in contact with moist soil. Deep seeding may reduce emergence and increase the risk of disease infection from soil-borne pathogens.
Information adapted from the Saskatchewan Ministry of Agriculture.