If your farmer-customers regard soybeans as the crop they just need to plant, spray and harvest, then tell them to think again. With that attitude, they will miss out on untapped yield potential, according to Farm Journal Field Agronomists Ken Ferrie and Missy Bauer. Here are three steps that will help growers get a strong start with soybeans this season
1. Plant soybeans early, like corn
Bauer notes, “Early planting allows earlier canopy closure, which increases total sunlight interception and allows plants to transpire more available water.”
She offers five practical recommendations:
• Respect soil temps: Plant once daily soil temps
average 55°F to 60°F.
• Population: Don’t overplant; if possible, use variable rate planting.
• Planting depth: Aim for 1.25’’ to 1.5’’ deep, and plant into moisture.
• Planting passes: Good ones give consistent planting depth and
• Seed treatments: They are often warranted in early planting and high residue. If Sudden Death Syndrome is an issue,
use one. Pick a treatment specific to that problem.
2. Keep soils in the pH ‘sweet zone’
“Soil pH is an important factor with soybeans,” Ferrie says. “As soon as we let pH slide, we run into trouble.”
Their root systems make soybeans so sensitive to acidity. “Soybeans have a taproot concentrated in one area,” he says. “The roots release hydrogen, which creates an area of concentrated acidity around them.”
Your farmer-customers may have observed this effect without realizing it if they 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 explains. “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.
“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,” he adds. “That acidity will shut down the soil microbes. Keeping soil pH in the sweet zone results in more consistent soybean yields.”
3. Balance soil fertility, especially P and K
Potassium plays a big part in soybean yield because it is involved in water management and disease prevention.
In addition, Ferrie advises that you keep an eye on magnesium levels, especially if a field is high in phosphorus–for example, from overapplication of manure. “If soil magnesium levels are low, we tend to see magnesium deficiency in soybean plants,” he says. “You may need to make an application of K-Mag or dolomitic limestone to fix the problem.”
Speaking of problems, don’t expect nitrogen to help a soybean crop. Ferrie notes that applying nitrogen in the spring may make soybeans look good because they usually don’t produce their own nitrogen until the third to fourth trifoliate, but it usually has little effect on yield and sometimes even lowers it.
“Typically, having excess nitrogen available makes soybeans lazy about nodulating and producing their own nitrogen,” he says. “In general, concentrate on phosphorus and potassium.”