Plant soybeans like corn—1" to 1½" deep and when soil temperature is above 55°F in the Corn Belt or by the calendar in the South. If your field gets off to a rocky start, don’t give up; soybeans set their yield later in development than corn.
Be Proactive and Hope the Weather Cooperates
Soybean germplasm possesses a lot of untapped yield potential, says Farm Journal Field Agronomist Ken Ferrie. But there’s no cookbook recipe that is guaranteed to bring it out.
That’s because so much of soybean yield is based on environmental conditions. The high soybean yields experienced by many farmers in 2010 may have resulted from unusually good growing conditions.
However, Ferrie explains, "We’ve seen things in our 20 years of on-farm studies that make a difference in yield and do it consistently enough that we know we should pay more attention. They help set the stage for maximizing yield when the environmental conditions are right."
Ferrie shared those tips with attendees at Farm Journal’s 2010 Corn College, which featured the first-ever soybean bonus session. (Learn more about Soybean College.)
1. pH is critical.
Don’t let soils get acid. "Soil pH is an important factor with soybeans," Ferrie says. "As soon as we let pH slide, we run into trouble."
It’s their root system that makes soybeans so sensitive to acidity.
"Instead of grassy roots, like corn, which spread out through the soil, soybeans have a taproot concentrated in one area," he explains. "The roots release hydrogen, which creates an area of concentrated acidity around them."
You may have observed this effect without realizing it if you ever planted soybeans in an alkaline field with a high soil pH. "During dry periods, the soybean plants look green and healthy because the acidity produced by the roots counterbalances the alkalinity of the soil," Ferrie says. "But then you get a rain, which washes the acidity deeper into the soil. The soil becomes alkaline, nutrients are tied up and unavailable and the soybeans turn yellow."
Acid soils will have poor nutrient release; regardless of what your soil test says, you won’t get nutrients into the plant. Acid soils will kill off the rhizobium bacteria, which are responsible for nodulation.
"Your soil may be at a marginal pH of 6.1 in mid-April; but if it gets hot and dry in June and July, your pH could dip in the zone around the taproot," Ferrie adds. "That acidity will shut down the soil microbes.
"Keeping soil pH in the sweet zone results in more consistent soybean yields," he concludes.
2. Manage alkaline soils.
Alkaline soils are prone to micronutrient deficiencies, which can have a critical effect on yield, Ferrie says. "In some calcareous, high-pH soils, it might be best to take soybeans out of the rotation. If you decide to plant soybeans, find a variety that can handle that situation."
- Late Spring 2011