Nitrogen fixing may not dramatically affect yield
As a growing body of research indicates, nitrogen fixing microbials may not help farmers significantly improve their corn yields.
Dr. Charlie White, soil fertility and nutrient management at Penn State, presented “Nitrogen Fixing Microbials for Corn: What We’ve Learned from Four Years of Field Trials” at the recent Corn Congress hosted by CCE’s Northwest New York Dairy, Livestock & Field Crops Program.
“It’s always been the holy grail to grow corn crops without nitrogen as it’s one of the most expensive inputs,” White said.
His research compared several commercially available products with nitrogen fixing microbes as their active ingredient, though White noted that “there are hundreds of other products.”
The 2022 research indicates that Pivot Bio’s PROVEN 40 can replace up to 40 lbs./acre of nitrogen (N) fertilizer in corn. It was applied in-furrow at planting and N was applied at three rates: none (control), 110 lbs. and 150 lbs.
Although not necessarily recommended for reducing N application, Corteva’s Utrisha N may help prevent N from becoming a yield limiting factor, or as White put it, “an insurance policy for nitrogen limitations.”
The Penn State researchers did a foliar application at V6 and applied N at the same rates as PROVEN 40.
Azotic North America’s Envita reduced N needed by crops by 27%. It was applied in the test plots in-furrow at planting and foliar at V6 at the same rates as the other treatments.
“Most companies recommend compatibility about starter fertilizer,” White said. “We used water to be purists.”
All the N was side-dressed and nothing went on at planting.
Envita foliar application resulted in an 11 bu./acre increase averaged across all N rates. The yield declined between 110 lbs. N/acre and zero N/ acre for all products.
In 2023, Penn State researchers added Accolade from Verdesian Life Sciences in furrow at planting at four N rates (70, 110, 150 and 190 lbs./acre). The control areas included the same N application rates. Corn was the previous crop on the plots.
“It had a little starter fertilizer at planting,” White said.
Accolade, Envita foliar, Envita in furrow, Pivot Bio and Utrisha all performed nearly the same for ear leaf stage results, with Envita foliar having only a slight advantage over the rest.
White noted that 2023 was a “decent growing season that started dry, but rain stopped after planting for six to seven weeks, which may have affected yield.”
Like the similar N levels at ear leaf, the grain yield results were nearly identical among the brands.
Also in 2023, White’s team conducted a test for Pivot Bio away from the public trials. Grain yield averaged 164 bu./acre compared with the 142 bushels of the control. The higher the side-dress of N, the higher the yield.
“We got very different results,” White said. “It was a different hybrid. It would be nice if we could get results like this on a more consistent basis.”
In the 2024 trial, the researchers irrigated to alleviate water stress from the crop. They achieved similar ear leaf results among all of the products. The significant main effect of the N rate was the ear leaf percent increased with N applied up to 150 lbs./acre.
The grain yield results were also similar to 2023, with 150 lbs. proving the “sweet spot” of N applied with optimal yield.
“There’s still a lot more we need to learn,” White said. “Why did they work sometimes and sometimes not? What drives that?”
He noted that timing of rainfall and dry periods likely affected the efficacy of in-furrow microbial treatments.
“These are well-researched products from reputable companies utilizing some of the most advanced biotechnology in the industry,” White said. “As with all biological organisms, many factors can affect performance and you should expect that results will vary. Test these products on a limited scale with your eyes open. I wouldn’t necessarily put it on your whole farm but put it on a few strips with check strips. They’re probably not ready for widespread use.
“There’s probably more gain to be squeezed out of your agronomy program by looking at your ‘4 Rs’” – those being right source, right rate, right time and right place.
In addition to the 4 Rs for nutrient application, he encouraged farmers to not look at microbial treatments as a replacement for implementing advanced and adaptive N management.
“These microbial products are not free,” White added. “Your biggest ROI may be adjusting other nitrogen management practice first.”
