Connecting Soil Health to Nitrogen Use Efficiency in Maine Potato Systems.

Commodities

• Agronomic: potatoes

Practices

• Crop Production: cover crops, crop rotation, nutrient management
• Education and Training: on-farm/ranch research
• Soil Management: soil quality/health

Potato farmers in Maine are increasingly interested in adopting regenerative practices to enhance soil conditions and support production in a system that places high pressure on soils. Many growers are already investing time and resources into longer rotations, cover crops, and reduced disturbance to improve soil health. While soil health is valued, we still lack an understanding of how soil health indicators affect agronomic outcomes, such as yield, tuber quality, and nitrogen (N) use efficiency (NUE).

As soil health develops gradually and must be evaluated within the context of management history, our project partners with Maine potato growers who are already engaged in regenerative practices to understand whether and how soil health can support more efficient N use in potatoes. Two participating farmers, along with Maine's State Soil Scientist and a representative from McCain Foods, serve on the project advisory committee to ensure the work remains aligned with farmer priorities and industry needs related to soil health and potato production. Specifically, our goal is to determine whether differences in soil health, shaped by established regenerative management, influence potato N responses and NUE, and whether these variables are more responsive than yield alone.

The three-year project includes two years of replicated on-farm trials, with outreach beginning during project conceptualization as farmers participated in defining priorities and on-farm experimental designs. Participating farms will represent a range of rotations and cover crop strategies, and replicated N rate strips ranging from 0 to 300 lb N/ac will be installed on each farm, with plot sizes adapted to each operation. Soil and plant samples will be collected to measure soil health indicators, potato yield, tuber quality, and NUE, allowing us to evaluate how existing soil conditions influence crop response to N fertilizer.

The project is led by Julia Barra Netto-Ferreira, Assistant Professor of Agronomy and Agroecosystem Health at the University of Maine, in collaboration with specialists in potato breeding, soil science, and statistics. Farmer engagement is built into the project, with on-farm trials serving as opportunities for scientific exchange and as demonstration sites that support peer-to-peer learning. Outreach is also complemented by more structured activities such as field days, grower meetings, extension publications, and presentations. Together, project activities will generate data under real farming conditions that support the adoption of regenerative practices in Maine potato systems by directly linking soil health indicators to N management and production outcomes.

The objective of this project is to evaluate whether and how soil health can support more efficient N use in potatoes and potentially reduce inputs without compromising yield or quality. We will test the hypothesis that potato fields with greater adoption of regenerative practices exhibit improved soil health indicators and greater NUE, even if yields are comparable to those of conventionally managed fields.

We will conduct experiments along a gradient of regenerative management conditions on research and commercial potato farms. Nitrogen rate strip trials will be established to generate a range of N availability, allowing the measurement of soil health indicators, plant N content, and potato production.

This research will generate field-based knowledge linking soil health indicators to agronomically meaningful outcomes, including NUE, yield, and tuber quality, under field conditions. We will develop a framework connecting soil health indicators to N performance, providing Maine potato farmers with information to guide soil health management. By identifying where soil health contributes to production benefits, this project will help farmers assess, interpret, and invest in regenerative practices in systems where building soil health is inherently challenging due to short rotations and intensive mechanization.