With erratic rainfall this summer, our soybean planting window has been extended into July in places across the state, especially if following small grain. Over the last three years, Clemson has conducted several research trials evaluating ultra-late planted soybeans, double-cropped behind corn. I have compiled a table below that highlights some of the research findings that can be applied to July-planted or ultra-late double-cropped soybeans. I am also including a link to a video that Dr. Bennett Harrelson put together based on this research. Click Here for Video for Double Crop Corn/Soybean
Insights from Clemson’s trials (2022–2024, Edisto REC in Blackville) include:
| Practice | Recommendation |
|---|---|
| Corn planting | Mid-March |
| Corn harvest moisture | ≥ 20% moisture, with off‑field drying |
| Soybean maturity group | Group V (Indeterminate 5); Group IV underperforms |
| Planting window – soybean | July–early August (stop ~Aug 7–10) |
| Seeding rate/spacing – soybean | ~150,000 seeds/acre on 30″ rows |
| Nematicide use | Counter 20G (on corn) + AgLogic (on soybean) + SRK resistant variety recommended (soybean) |
| Nitrogen & row spacing effects | No significant yield benefit from at‑plant N, narrower rows, or higher seeding beyond identified rates |
