Research continues in quest for higher soybean yields

High soybean prices and increased genetic potential have driven producers to search for common practices that can boost soybean yields and increase profits. Starter nitrogen application, foliar nutrient application and new, slow-release N products have gained attention in the past few years as methods to boost yields.

In 2011, University of Nebraska Extension researchers studied soybean yield response to nutrient management practices in two sets of field trials. The “starter/foliar” trial and the “high-yield” trial were both conducted at the four on-farm Soybean Management Field Day sites near Bancroft, Elba, Clay Center and Cortland.

At a glance

Growth-promoting treatments, nutrient application didn’t sufficiently boost yields.

Similar treatments have proven profitable where the growing season is shorter.

UNL researcher says that more work can be done studying row spacing.


According to UNL Extension nutrient management specialist Charles Wortmann, the “starter/foliar” trial evaluated starter nitrogen application and foliar application of nitrogen, phosphorus, potassium and magnesium, along with micronutrients.

In the “high-yield” trial, researchers evaluated treatments like clipping of plants or Cobra application at the second trifoliate growth stage to increase branching and the opportunity for pod set. Growth promoters and inoculants with growth promoters to increase root growth and nodulation, as well as soil fertility treatments were also evaluated.

The trial fields were planted in early May at each of the sites, and seedling establishment was slowed due to cool weather. At the Bancroft site, researchers had the opportunity to study high-residue cover, rated at 95%. Residue at the other sites ranged between 45% and 65%.

In the starter/foliar trial, the mean yield was 66 bushels per acre, with the high yield trial producing a lower mean yield. Foliar nutrient applications at the R2 stage increased mean yield by 1.9 bushels per acre, but the increase did not justify the cost. The treatments did not affect yield significantly, except that the clipping and Cobra treatments reduced yield, Wortmann says. So researchers are generally not recommending routine use of these methods.

“Starter nitrogen is commonly beneficial in areas of a shorter growing season, such as the High Plains,” Wortmann says. For instance, similar nutrient treatments resulted in 6% yield increase at Brookings, S.D. “Available evidence indicates that we cannot expect much response from the treatments studied, although they have not been evaluated much at high yield levels above 85 bushels per acre,” he says.

On average, corn yields run about 3.3 times the mean soybean yields. “Production of oil and protein takes more energy than production of starch, therefore soybean yields are expected to be much less than corn,” Wortmann says. “The photosynthesis system of the soybean and many other crops differs from and is less efficient than that of corn or sorghum.”

But Wortmann says there is more research that can be done. “We need to look at row spacing more closely, as well as the interaction of row spacing with fungicide application,” he says. “Reevaluation of the results of research on soil-applied nitrogen at early pod development, through fertigation for instance, suggests that we should look at nitrogen applied at the R4 stage.”

If you’d like more information on research being conducted on boosting soybean yields, plan now to attend a 2012 Soybean Management Field Day this summer, or you can contact Wortmann at 402-472-2909 or email cwortmann2@unl.edu.

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MORE STUDY NEEDED: UNL Extension researchers will continue to look at new methods and treatments to boost soybean yields.

This article published in the March, 2012 edition of NEBRASKA FARMER.

All rights reserved. Copyright Farm Progress Cos. 2012.