The best time to plant soybeans in Oklahoma is from late April through May, once soil temperatures consistently reach 50°F or higher. Planting in June is still possible, especially in double-crop systems after wheat harvest, but yields drop noticeably the later you go.
The Main Planting Window: Late April Through May
April and May make up the early planting period for Oklahoma soybeans. The key trigger isn’t the calendar date itself but soil temperature. Most soybean agronomists recommend waiting until soil temps hit 50°F and are forecast to stay there for at least 24 to 48 hours. At that point, the seed can absorb water and germinate normally. If soil is still cold during that initial moisture uptake, membranes inside the seed don’t rehydrate properly, causing what’s known as chilling injury. Damaged seedlings emerge slowly or not at all.
In practice, soil temperatures in central Oklahoma typically cross that 50°F threshold in mid to late April. The average last frost date in the Tulsa area is March 29, and by late April the risk of a hard freeze is essentially gone. Southern Oklahoma warms up a bit earlier, while the Panhandle and far northern counties may not reach consistent planting conditions until early May.
For the strongest yields, aim to get your soybeans in the ground during May. Research across the southern Great Plains consistently shows that early-to-mid May planting gives soybean plants the longest possible growing season before days start getting shorter after the summer solstice on June 21. Since soybeans are photoperiod-sensitive, meaning they use day length as a signal to shift from vegetative growth to flowering and pod fill, extra weeks of long days translate directly into taller, bushier plants with more nodes to set pods.
What Happens When You Plant Late
June planting is common in Oklahoma, but it comes at a cost. Yield loss data from university research shows that planting after late May reduces soybean yields by roughly 15 to 16 percent, which works out to about 11 bushels per acre compared to an optimal planting date. Push into mid-June or later and losses climb to 10 to 15 bushels per acre. Every week of delay compresses the vegetative growth phase, so the plant flowers at a shorter height with fewer pod-bearing nodes.
The decline isn’t just about shorter days. Late-planted soybeans face hotter conditions during flowering and pod fill in August, when Oklahoma temperatures regularly top 95°F. Heat stress during bloom can cause flower abortion, and dry spells hit harder because the root system of a smaller plant explores less soil volume.
Double-Crop Soybeans After Wheat
Many Oklahoma growers plant soybeans immediately after harvesting winter wheat, which typically puts planting 30 to 45 days later than the normal window. That means most double-crop soybeans go in the ground around mid-June, with emergence happening right around the summer solstice or shortly after.
Because these plants have less time to grow before shortening days trigger reproduction, choosing the right maturity group matters more than it does for full-season plantings. Shorter-season varieties (maturity groups IV to early V for most of Oklahoma) give double-crop soybeans a better chance of completing pod fill before the first fall frost. Even with the right variety, double-crop soybean yields typically run lower than full-season yields, but the combined economic return from wheat plus soybeans often makes it worthwhile.
Planting Depth and Soil Considerations
Soybean seed should go 1 to 1.5 inches deep in most Oklahoma soils. If you’re working in heavier clay loams or fine-textured soils, stay toward the shallower end of that range because those soils can crust over and make it harder for the emerging seedling to break through. On sandier ground, you can plant up to 2 inches deep to reach better moisture, but don’t go deeper than that.
Soil moisture at planting depth is more important than sticking to a rigid calendar date. If April soil temps are warm enough but the top two inches are bone dry, it’s worth waiting for a rain event rather than dropping seed into dust. Soybeans need to absorb roughly 50 percent of their weight in water to start germinating, so dry conditions at seeding depth will leave you with patchy, uneven stands.
Quick Reference by Region
- Southern Oklahoma: Planting can begin in mid to late April when soils warm fastest. Full-season varieties in maturity group V work well here.
- Central Oklahoma: Late April through mid-May is the sweet spot. Maturity groups IV to V are standard.
- Northern Oklahoma and Panhandle: Early to mid-May is more realistic given later soil warming. Maturity group IV varieties give the best fit for the shorter frost-free season.
- Double-crop (statewide): Mid-June, immediately after wheat harvest. Use the shortest-season variety adapted to your area.