
You want to build a road map to higher soybean yields. Where should you start? Is soil fertility most important? How about seed treatments?
Fred Below was charged with determining the secrets to achieving higher soybean yields over a decade ago by the Illinois Soybean Association. After years of work by the University of Illinois agronomist and his graduate students, he reveals six factors, ranked by importance.
“First, if you’re shooting for 80-bushel-per-acre soybeans, there are certain prerequisites,” Below says. “You need good soil structure and adequate drainage, excellent weed control, plus soil pH and phosphorus and potassium levels must be adequate.”
Here is Below’s list in order, based on research findings, complete with how many bushels each factor likely contributes:
1. Weather: 30-plus bushels. Will you have too much rain early, too little rain late, or frozen precipitation as hail?
“The real impact of too much rain early is what it does to planting date,” Below explains. “Our three-year trial, just completed in ’24, indicated that for each day of delay in planting soybeans after April 23, we gave up over a half-bushel of yield potential. When conditions allow, it likely pays to plant soybeans before corn.”
Data from Osler Ortez, Laura Lindsey and Taylor Dill shows similar results. The Ohio State University researchers, in the middle of a three-year project comparing whether it pays to plant corn or soybeans first, indicate that so far, planting soybeans first appears to often be a winning strategy, especially in western Ohio and Indiana.
Shawn Conley, Extension agronomist at the University of Wisconsin, reached the same conclusion. “If soils are right in mid-April, plant soybeans,” he says. “If you have two planters, start them both on soybeans.”
2. Genetics and variety selection: 30 bushels. “Some guys spend lots of time deciding which corn hybrids to plant, and then just grab a soybean variety,” Below says. “That is the wrong strategy. Variety selection in soybeans absolutely matters.
“In our three-year soybean management trial where we compared varieties, we saw a 32.3-bushel-per-acre range between the highest- and lowest-yielding varieties at an early planting date, and an 11-bushel difference at later planting dates.”
3. Row spacing: 7 bushels. “If you are planting early, row spacing doesn’t matter. But if you are planting later, you want narrower row spacing to get canopy closure quicker,” Below says. “We compared 30-inch rows versus 20-inch rows in our trials, and 20-inch rows excelled at later planting dates.”
4. Foliar fungicides and insecticides for plant protection: 6 bushels. This one is independent of planting date, Below says. Scout and control diseases and insects when necessary.
5. Soil fertility: 5 bushels. To grow 80-bushel-per-acre soybeans, you need lots of soil fertility, but that doesn’t equate to adding lots of fertilizer. Remember, having P and K in order is a prerequisite. This may become more of a factor with late-planted beans, because daily demand for nutrients is higher for later plantings.
6. Seed treatments: 2 bushels. Naked seed without treatment is cheaper, and if you plant late, you don’t need seed treatments, Below says. But if you plant early, as recommended, using seed treatments for pest control helps.
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