South Dakota has a short growing season compared to other midwestern states. Soybeans maturity or when they enter reproductive phase of the lifecycle is based on the length of daylight hours. The longest day of the year is the summer solstice or June 20. After June 20, the duration of daylight shortens. It is important to plant soybeans as early as you possible can in South Dakota because of our short window in the growing season.
Farming is about managing risk. When you look at the last frost date and cost of replanting, it may make sense to plant soybeans early in order to capture more growing days prior to June 20.
50 Percentile Last Spring Frost (32°F) Day Occurrence
Plant early, plant early, plant early!
Potential yield loss occurs with delayed planting of soybeans. SDSU research funded with SD soybean checkoff showed that soybeans will lose 0.25 to 1 bushel per acre per day when planted after the optimum planting date. The optimum planting date varies with location and variety.
Crop Insurance Deadline
The last date of planting soybean for insured counties in Eastern South Dakota is June 10.
Row Spacing & Seeding Rates
Row spacing and seeding rates can impact yield of soybean production in South Dakota. SDSU research showed in a small plot study that moving from 30 inch rows to 15 inch rows increased yield up to 20 bushels per acre. However, research conducted on-farm following these results showed a 2 bushel per acre increase. A major “kitchen sink” study completed by the University of Minnesota and funded with the help of the soybean checkoff found a 6-7 bushel increase in yield when moving from wide to narrow row spacing.
Seeding Rate Recommendations
What’s New in Research?
New planting equipment will allow a farmer to plant a variable seeding rate or variable variety of soybeans across a field. The operator can adjust seeding rates based on topography and soil type. The variable variety seeding will allow a farmer to plant many varieties in a given field to optimize the plants specific growing conditions such as soil type.