Obtaining adequate soybean stands can be challenging in light of the fact that a lot of lower quality soybean seed has been brought to the farm this year.

Germination test rates have been noted from 75% to 90%. Let’s look at seeding rates for a variety that averages 2,700 seeds per pound at three different germination test ratings. The goal is 180,000 plants per acre from 180,000 Pure Live Seed (PLS).

90% germ x 2700 seed/lb = 2430 PLS/lb
180,000 ÷ 2430 PLS/lb = 74.07 lb/acre seeding rate

85% germ x 2700 seed/lb – 2295 PLS/lb
180,000 ÷ 2295 PLS/lb = 78.43 lb/acre seeding rate

75% germ x 2700 seed/lb = 2025 PLS/lb
180,000 ÷ 2025 PLS/lb = 88.88 lb/acre seeding rate

If you expect seed loss greater than that accounted for by germination test, adjust seeding rates accordingly. For example, if you expect an additional 5% field seed loss from a combination of cold soil, planter seed damage, and insects, run the numbers for 90% germination seed at the 85% germination level (10% loss to germination + 5% field loss) for an accurate seeding rate.

% germination – % field loss x # seeds/lb = PLSS/lb
PLSS/acre ÷ PLSS/lb = lb acre seeding rate

When we factor in field loss and subtract it from germination loss we end up with the projected Pure Live Seed Survivors (PLSS) (see equation above).

Early planted soybeans have been slow to establish. Soybean stand assessments should be done as soon as the crop is fully emerged. Early assessments allow for inter-seeding of thin stands. Significant delays in possible replant decision may require the complete reestablishment of soybean field(s) with inadequate stands. Do the math ASAP.

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