According to Dr. Jeremy Ross, a soil fertility professor and soybean Extension agronomist for the University of Arkansas, soybean yields in the Eastern U.S. could set a new record this year, with each acre yielding an estimated 53 bushels on average. This would pass the previous mark of 52 bushels/acre, which was achieved in both 2021 and 2022.

This increase comes despite drought-like conditions experienced in certain portions of the U.S. in 2023. Ross listed growing practices such as proactive irrigation, improved plant genetics and early planting as factors contributing to improved yields.

“Each year our soybean yields just keep getting better and better, and that trends across the entire United States,” Ross said. “Looking back, we were 20 percentage points ahead of the five-year average on planting progress and that translated into the crop being mature 15% to 20% beyond where typically we were.”

“When we’re looking at fertilizer and nutrients for soybeans, and pretty much any other row crop, it’s pretty complicated,” Ross continued. “It’s the most complicated system in row crop production.”

He said this is due to having to deal with a number of nutrients, different soil textures, soil moisture levels and pH levels. Nutrients are the foundation that sustain biological functions, and they help protect plants from stressors while supporting overall yield.

“Soybeans require a number of elements. First we have the macronutrients nitrogen, phosphorus and potassium. Those are the three big ones everyone focuses on. But it’s important not to forget the secondary micronutrients – calcium, magnesium, iron, boron, manganese, zinc, copper, molybdenum, chlorine and sulfur,” he said. “The importance of those cannot be overlooked.”

Soybeans yields are growing – so support their soil

Dr. Jeremy Ross, a soil fertility professor and soybean Extension agronomist. Photo courtesy of Fred Miller

Ross also noted that the pH level of the soil should remain between 5.5 and 7.0, with an optimal range being between 6.3 and 6.5.

But as croplands turn out bigger soybean crops, it’s important to be mindful of the toll that takes on the soil.

“Increasing soybean yields are removing more and more nutrients,” said Ross. “One bushel of soybean crop removes four pounds of nitrogen, 0.4 pounds of phosphorus, 1.25 pounds of potassium and 0.2 pounds of sulfur.”

Deficiency symptoms, including an unhealthy yellowing of leaves, may appear in a soybean crop if any nutrient levels are limited. Stresses that can cause symptoms include drought, temperature, compaction, saturated soils, root diseases, root feeding from soil insects, a pH imbalance, fertilizer burn and chemical injury to roots.

Ross recommended farmers have a really good soil test at the beginning of their planting to know just what sort of soil they’re dealing with. And it’s best to use a more in-depth history of soil test data. Using multiple years of tests can provide more of a progression than a snapshot of your soil and can help you make more informed decisions.

Ross recommended using a potash rate calculator to determine what soil adjustments can be made in-season.

by Enrico Villamaino