Improved dry bean rhizobium inoculant technology and farmer adoption in the North Central region

Commodities

Practices

The North Dakota-Minnesota region is a center for dry bean production. Of the 1.39 million U.S. dry edible bean acres planted in 2025, 710,000 acres were in North Dakota and 340,000 in Minnesota, representing more than 2,400 farms. Despite being a legume capable of fixing nitrogen through symbiosis with Rhizobium, nitrogen fertilization remains as the standard practice: 93% of farmers apply N fertilizer, while only 19% of North Dakota growers report using inoculants. With recommended application rates of ~70 lb N/acre, this represents roughly 73.5 million lb of nitrogen-valued at an estimated $24.36 million per year that could be reduced.

However, urea has consistently outperformed current inoculants in dry bean yield. Existing Rhizobium strains often fail to provide high, reliable levels of N-fixation, and their effectiveness can be limited by soil pH, moisture, and temperature. We hypothesize that the failure of available options is due to a lack of biological innovation in available inoculants. More competitive strains, better adapted to regional conditions, could increase biological N-fixation and substantially reduce reliance on synthetic fertilizers.

This project will use high-throughput screening technology to identify elite Rhizobium isolates from regional soils. Top-performing strains will be evaluated under field conditions across regions, and market classes to determine whether tailored inoculants to regions or varieties are warranted. The outreach and testing component includes multi-site field trials across key dry bean-growing areas, which will serve both as research evaluations and as demonstration plots for extension activities.

Objectives:

• Identify elite, locally-adapted rhizobium strains for dry beans
• Validate dry bean yield improvements by new inoculant strains in regional plot trials
• Promote the use of inoculants in the area to reduce the application of N fertilizers.

Outcomes:

• Reduction of N fertilization in the area, thereby lowering production costs for dry bean producers and reducing ecological impacts for public stakeholders broadly
• Locally adapted, elite ND-MN Rhizobia strains will be identified and made available for licensing to inoculant companies (eg. Lilac Agriculture). We anticipate subsequent commercialization of these products and their availability to dry bean producers in the North Central Region.
• Increased awareness of the implications of employing local rhizobia strains rather than N fertilization, focusing on reducing ecological impact and financial risks.