Yields are declining across thousands of acres in western North Dakota due to soil acidification. The prolonged use of nitrogen fertilizers, coupled with slightly acidic soil parent materials and weakly buffered soils, has resulted in soil pH dropping below 5.5 in many cultivated areas. This strong acidity negatively affects nutrient availability, root growth, and soil microbial activity due to aluminum (Al) toxicity. Among the soil microbes that are negatively affected by low soil pH are rhizobia. Rhizobia are crucial to ensure optimum soybean yields, as they directly affect soil fertility and crop productivity by fixing nitrogen (N) from the atmosphere into the soil. When soil pH drops below 6.0, the development of the plant's root hairs is impaired, hindering the formation of nitrogen nodules. Furthermore, soybean is a relatively new crop in western North Dakota, which causes most soils in the region to lack naturally occurring Rhizobium populations—a condition further aggravated by low soil pH. Little is known about the interaction between different Rhizobium strains and soil pH on soybean development and nodulation. This study aims to evaluate the effects of soil pH, on three different Rhizobium strains and its effect on soybean development and nodulation.

• Evaluate the effect of low soil pH on different Rhizobium strain’s activity.
• Evaluate growth and biomass of soybean as an effect of the interaction between different
Rhizobium strains and soil ph.
• Increase the knowledge base of soybean inoculation and acidic soil management in North
Dakota by promoting outreach activities.

• Create an extension publication on soybean inoculation in acidic soils in North Dakota.
• Results will be included in research extension center annual reports, Western Dakota Crops Day booklet, and will be presented at workshops and meetings across the state at the county and regional level. Results will also be disseminated through social media platforms, local radio, agricultural newsletters, and other media outlets.
• One research paper will be published in a peer-reviewed journal.

Soybean cultivation is still relatively new in western North Dakota, resulting in limited region-specific guidance on optimal crop management practices. This research will directly benefit soybean farmers in the region by providing updated, evidence-based recommendations for soybean inoculation, particularly in acidic soils.