In recent years, acres planted to wheat has increased substantially. In fact, the U.S. Department of Agriculture estimated a 12% increase in soft red winter wheat acres in 2021 versus 2020. This equates to roughly 670,000 more acres. So, why is there an increase in acres planted to wheat? The main reason is likely a great price, but may also include suitable fall weather, adding diversity to the farm, preventing soil erosion, or efforts to increase soil health. Regardless of the reason for planting wheat, a majority of the winter wheat crop will be followed with double-crop soybeans.
Growing wheat followed by double-crop soybeans was arguably the most profitable rotation in Southern Illinois in 2021. That, of course, depended on the price the farmer sold their grain and how much rain they received in August for the soybean crop. Often, the ultimate yield driver for double-crop soybean yields is late summer rains. This helps with pod retention and filling the pods with bigger seeds. While we have no control over late summer rains, there are several things we can do to set our double crop soybeans up for success.
Recipe for success:
Wheat Harvest: Since soybean plants are day-length sensitive, every day that passes can be crucial to soybean yield. The sooner we can plant soybeans before the summer solstice, the better, because once the summer solstice arrives the soybeans will start to flower. This results in the soybean plant slowing vegetative growth and can limit the number of nodes produced where pods and seeds will develop. Harvesting wheat at 18-20% moisture and drying the grain may be beneficial as compared to waiting until the grain is at 13% moisture. This can allow for an earlier planting date to help the soybeans maximize the yield potential.
Soybean Maturity: Maximizing the yield potential starts with the soybean variety. Selecting a later-maturing soybean variety is an extremely important ingredient for this recipe. A later-maturing variety will continue vegetative growth and will produce flowers and pods later in the season. In Southern Illinois, a typical first crop soybean variety maturity ranges from a 3.2 – 4.2, whereas a double crop soybean variety maturity ranges from a 4.2 – 5.0. A good rule of thumb can be to increase your double-crop soybean maturity one maturity group from the first crop soybeans.
Planting population and row width: Regardless of planting date, we always want to maximize the number of nodes/acre for any soybean crop. Since double-crop soybeans will be planted late, these individual soybean plants will not be able to branch out and produce as many nodes/acre as an April planted soybean plant would be capable of producing due to shorter day length. The largest driver to maximize the number of nodes/acre with later planted soybeans will be increasing planting populations. Beck’s Hybrids two-year PFR data from Henderson, Kentucky shows 200,000 plants/acre was the most profitable planting population for double crop soybeans. Furthermore, every treatment of 15-inch row double crop soybeans produced a higher return on investment (ROI) than every treatment of 7.5-inch row double-crop soybeans. Thus, double crop soybeans should be planted on 15-inch rows at 200,000 plants/acre. For more information on the study, click here.
Residue Management: Residue management can be a large challenge when planting double-crop soybeans especially when no-till planting into the wheat stubble. No-till can provide many benefits including saving time, retaining soil moisture, and not incorporating wheat straw into the soil that may tie up essential nutrients for crop growth and development. Residue management begins with the combine. We must ensure that the combine is spreading the residue evenly and it is not clumping or bunching the residue. This could prevent proper seed to soil contact and inconsistent planting depth. Planters should be equipped with row cleaners to move residue out of the seed trench so we can ensure proper seed placement. Beck’s Hybrids two-year PFR data from Henderson, Kentucky shows at least a 1.5 to 2 bushel/acre yield advantage when utilizing row cleaners. For more information on the study, click here.
Disease/Insect Management: Double-crop soybeans often endure much higher disease pressures, insect pressures, and higher temperatures which leads to higher stress levels. Fungicide applications can alleviate some of these stressors. Beck’s Hybrids two-year multi-location PFR data from Southern Illinois and Kentucky shows that a fungicide application at R3 provided just shy of $30/acre advantage compared to no fungicide application. Even though double crop soybeans are the last thing planted, we still need to manage them as if they are the first thing planted. For more information on the study, click here.
Recap: So, when it comes to planting double crop soybeans, the recipe for success includes:
- Harvest wheat at 18-20% moisture
- Select a later-maturing soybean variety
- Plant the double crop soybeans at 200,000 plants/acre on 15-inch rows
- Spread the wheat straw evenly during wheat harvest and utilize row cleaners when planting the double crop soybeans
- Apply a fungicide at R3 if disease pressure and crop stress levels are high.