Putting in a crop of soybeans following wheat can really boost your income. Adequate moisture at planting, seeding rate, planting date and maturity are some important issues to consider before making the commitment. Rainfall in August and escaping an early frost are things we can’t control, but are essential for a successful crop as well.
It takes a soybean plant around 90 days to reach physiological maturity, so the first thing to consider is when the wheat crop will be harvested and average first frost date. The following is an average of graphs from different sites across the Midwest:
First Average Frost
- Nebraska, Iowa and Colorado Oct. 5-1
- Kansas, Illinois and Indiana Oct. 15-20
- Missouri, Kentucky and Boot Hill Oct. 20-25
If we take Illinois, for example, and use Oct. 15 as a frost date, you would subtract 90 days, which would put the target date for planting double-crop soybeans on July 18 for the crop to reach maturity.
The biggest mistake we see with double-crop soybeans is: “If I'm double-cropping soybeans, I'll need an early variety.” This is not the case. We only have so many days for the crop to mature. Planting a medium to mid-late soybean will usually provide more height and yield. Taller plants set more pods, which equals increased yields.
Population and row spacing are other factors that can also gain yield. Higher population pushes the first pod on plant higher, which will lead to combine cutting more harvestable pods. Planting into wheat stubble may cause the loss of a few soybeans, so seeding an extra 15-20,000 seeds will help stand establishment.
Narrow rows for late planting are also a plus. Planting 30-inch-row soybeans will not canopy and close the rows for better weed control. If you have a 30-inch-row planter, just double back and split the rows. Studies have shown a 15-20% yield increase in narrow rows with late-planted soybeans.
In conclusion, there are several factors when deciding to plant a crop of soybeans after wheat. If soil moisture is adequate and wheat harvest is timely, planting a crop of beans is a definite option for adding profit. There are variables we cannot control such as timely rains in August and frost. But planting a mid- to fuller-maturing soybean and increasing population are things we can control to increase yield potential.