Biological Nitrogen Fixation in Corn: Wisconsin Trial Results

Introduction

Interest in biological products that aim to provide nitrogen to nonlegume crops by fixing atmospheric nitrogen for non-legume grain crops has increased in recent years. While inoculating legumes like alfalfa and soybeans with symbiotic rhizobia bacteria is a way to facilitate the process of converting atmospheric nitrogen into a plantusable form, nitrogen supply from bacteria which asymbiotically fix nitrogen in crops like corn is unknown. University of Wisconsin–Madison conducted field trials to examine if a popular gene-edited asymbiotic nitrogen fixer bacterial product, PROVEN 40, affected corn grain yield or corn grain yield response to nitrogen fertilizer.

Materials & Methods

Trials were conducted at five locations in Wisconsin in 2023. The trials were arranged as standard nitrogen rate trials that included four to eight nitrogen rates per location and treatments with and without gene-edited N fixers (PROVEN40). Gene-edited nitrogen fixers (GENF) were applied following the label in-furrow at Arlington, Arlington 2, Dane Co., and Jefferson Co. locations. It was applied following the label as a seed treatment at the Green Lake location. Individual trial protocol summaries for each location are in Table 1.

	Dane Co.	Arlington	Arlington 2	Green Lake	Jefferson Co.
Planting date	5/16/2023	5/10/2023	5/18/2023	5/17/2023	5/10/2023
Product & Placement	In-furrow, non-chlorinated water, over top of seed	In-furrow, non-chlorinated water, onto the seed	In-furrow, non-chlorinated water, over top of seed	Seed treatment	In-furrow, well water, just underneath the seed
Starter Fertilizer Rate, lb N/ac	None	None	None	24 lb/ac N (Me SZ^a) broadcast applied into living cover	45 lb/ac N (32% UAN^b) banded except 0N
Fertilizer Source	Urea^c with NBPT^d	Urea with NBPT	Urea with NBPT	Urea with NBPT	32% UAN
Fertilizer Application and Placement	5/16/2023 Pre-plant	5/10/2023 Pre-plant	5/9/2023 Pre-plant & incorporated	6/9/2023 Broadcast	Y drop side-dressed
Nitrogen Rate, lb N/ac	0, 40, 80, 120, 160, 200, 240, 280	0, 40, 80, 120, 160, 200, 240, 280	0, 60, 120, 180, 240	0, 30, 60, 90, 120, 150, 180, 210	0, 100, 150, 200 (7, 105, 150, 200 including starter)
Harvest	11/17/2023	11/3/2023	11/16/2023	11/17/2023	10/30/2023

^a Me SZ: Microessentials SZ (12-40-0-10S-1Zn)
^b32% UAN: 32-0-0
^cUrea: 46-0-0
^dNBPT: N-(n-butyl) thiophosphoric triamide used as urease inhibitor.

Results

Dane County

Scatter plot graph showing the relationship between corn yield (bu/ac) and nitrogen rate (lb-N/ac) for two categories: Control (represented by red circles) and GENF (represented by blue triangles). Both categories show a general increase in yield as nitrogen rate increases. The graph includes regression equations for both categories: Control (R²=0.7933, y=166.85 + 0.86x -0.0015x²) and GENF (R²=0.7628, y=155.80 +1.07x -0.0022x²).

Arlington

Scatter plot graph showing the relationship between nitrogen rate (lb-N/ac) and corn yield (bu/ac) for two categories: Control and GENF. Both categories show a general increase in yield as nitrogen rate increases. The graph includes regression equations for both: Control (R² = 0.3493, y = 167.91+0.194x) and GENF (R² = 0.2699, y = 163.85 + 0.186x).

Arlington 2

Graph showing the yield (bu/ac) of Control and GENF against the nitrogen rate (lb-N/ac). The yield increases with the nitrogen rate for both, and GENF has slightly higher yield at most nitrogen rates. The graph includes regression equations for both: Control (R² = 0.9676, y = -0.0013x² + 0.6876x + 138.39) and GENF (R² = 0.9409, y = -0.0013x² + 0.6545x + 142.38).

Green Lake

Scatter plot graph showing the relationship between nitrogen rate (lb-N/ac) and yield (bu/ac) for two categories: Control and GENF. Both categories show a general increase in yield as nitrogen rate increases up to a point, after which the yield plateaus. The graph includes regression equations for both: Control (R² = 0.3493, y = 128.23+ 0.640x -0.0022) and GENF (R² = 0.2699, y = 124.18 + 0.693x -0.0024).

Jefferson

Discussion & Summary

While the concept of using gene-edited nitrogen fixing bacteria for corn and other non-legume crops to help meet crop nitrogen needs in Wisconsin is exciting, there is not significant, current evidence that there is a GENF product capable of accomplishing this.

In 2023 field trials at five Wisconsin sites, corn grain yield and corn grain yield response to nitrogen fertilization was not affected by the application of a GENF product. Continued research in varying growing environments around Wisconsin across multiple years will be useful to provide needed information for those considering the use of these and similar products.

Author's Note

This resource is intended as a quick reference; these products need more testing in Wisconsin, and the University of Wisconsin–Madison neither officially supports nor discourages their use in cropping systems. Always read, follow, and understand the product’s label and any included instructions.

Whenever trying new products for the first time on your farm, it can be helpful to start on a small scale across a few different areas, leaving untreated strips. This way, you can measure if there was an actual yield difference and whether the product’s return on investment (ROI) justifies its continued use or not. One of the most proven, efficient ways to reduce fertility inputs is through soil testing and the use of Nutrient Management Plans. To make one for your farm, contact the county conservation office or NPM specialist serving your area.

For more information on asymbiotic nitrogen-fixing products, refer to the publication “A review of common nitrogen biological products for corn,” available from UW–Madison’s Nutrient and Pest Management Program.

UW-NPM-GENF-WI-Results Download

Extension-biological-nitrogen-fact-sheet Download