Research Highlights
Adding Wet Distillers Grain to Soybeans for Nitrogen Fixation Benefits

Condensed distillers solubles (CDS), a co-product from ethanol production in syrup form, is applied to portions of soybean test plots in North Dakota. The CDS adds nutrients to the soil including nitrogen, phosphorus and sulfur. Photo: Jasper Teboh

By Carol Brown

The ethanol industry in the United States provides farmers with another option for selling corn. Most ethanol production uses starch from corn kernels to make fuel. The by-products of corn ethanol production still have use as they contain protein, fat, and nutrients. Because the by-products can be used elsewhere, they are considered co-products. One of the uses of this co-product is processed into distillers grain and used as livestock feed. 

Researchers across the Midwest are exploring other uses of distillers grain beyond feed. Jasper Teboh, a soil scientist at the North Dakota State University Carrington Research Extension Center, is studying whether distillers grain can be beneficial to a soybean crop. This research project is supported by the North Dakota Soybean Council.

“We wanted to assess if farmers could apply distillers grain to their fields as a source of nutrients and whether the nutrients would impact yields,” says Teboh. “We also wanted to examine whether high nitrogen supplied with distillers grain would impact nitrogen fixation in soybeans.”

Condensed distillers solubles (CDS) is a syrup co-product of corn ethanol production. CDS is used in livestock feed and researchers are exploring its value in other ways including as a soil amendment. Photo: Jasper Teboh

Teboh and his research team applied to soybean test plots wet distillers grain (WDG) and the liquid form called condensed distillers solubles (CDS). These co-products are rich in phosphorus, nitrogen, sulfur, and contain other macro and micronutrients, says Teboh, which are all beneficial nutrients.

“Soybeans will take up available nitrogen in the soil first because it spends energy fixing its own. It would rather take up free nitrogen in the soil,” explains Teboh. “We had anticipated that when urea was applied, the plant would easily take it up and fix less nitrogen than the slowly available nitrogen from the distillers grain, but that was not the case.”

The four test plots compared applied phosphorus (P) fertilizer and nitrogen (N) treatments:

  1. Control plot with no P applied; 30 lbs. N as urea applied to half the plot 
  2. 40 lbs. P as granular triple super phosphate (TSP); 30 lbs. N as urea applied to half the plot 
  3. 40 lbs. P and 30 lbs. N as CDS
  4. 40 lbs. P and 66 lbs. N as WDG.

“We found the application of WDG at 40 lbs. of phosphorus and 66 lbs. of nitrogen did not affect the rate at which nitrogen was being fixed,” he says. “I believe the reason is that the nitrogen released from the distillers grain is slow and it did not allow the soybeans to have access to high nitrogen. But the plant could take advantage of the nitrogen being released gradually as it fixes its own.” 

Teboh and the research team’s preliminary conclusion was that despite the application of 60 lbs. N and WDG, nitrogen fixation was not negatively impacted, since it was being released gradually into the soil. The main finding was that yields and nitrogen fixation were no different across all the treatments.

In a previous study, Teboh used distillers grain in wheat and corn with promising results for improving yield when it was applied as a source of phosphorus. 

“In this soybean study, we wanted to simulate a no-till situation, so we applied WDG and left it on the surface in half the plots then incorporated it into the soil on the other half to simulate conventional tillage,” says Teboh. “There was no difference in yield between the two.” 

The availability of distillers grain for farmers could be a benefit for corn or wheat, but according to Teboh and his research team, soybeans were not impacted by the addition of this co-product, probably because there was sufficient residual nutrients in the soil to satisfy the crop’s needs. But soybeans were not negatively impacted either. 

This project was funded by the soybean checkoff. To find research related to this research highlight or to see other checkoff research projects, please visit the National Soybean Checkoff Research Database.