Environmental Models Make Invisible Nitrogen Pollution Visible — and Manageable

(WASHINGTON, DC) Nitrogen (N) is essential for food production, but too much nitrogen accelerates climate change and impairs water quality. The challenge to date has been measuring how much excess nitrogen is being lost to the environment from agriculture, as existing methods are expensive, inaccurate and time consuming. Environmental Defense Fund's N-Visible framework, published today, overcomes these barriers.

N-Visible provides a user-friendly, scientifically robust way for farmers, farmer advisers, food companies and policymakers to measure agriculture's climate and water quality impacts. The framework uses N balance — nitrogen added to a farm field minus nitrogen removed during harvest — to measure excess nitrogen at the field level. It also uses aggregated N balance scores and two new environmental models to calculate environmental impacts at regional or national scales.

The open-source framework is now available for organizations and companies to reference and integrate into existing programs and software.

"The environmental models are a breakthrough for measuring progress on water quality and climate mitigation," said Eileen McLellan, lead senior scientist at EDF. "It's now easier than ever to show that conservation practices and sustainability initiatives are delivering quantifiable benefits for the environment."

N balance is the foundation of the N-Visible framework. For more than five years, EDF scientists and research partners at land-grant universities have demonstrated that N balance is a robust proxy measurement for how much nitrate has leached into waterways and how much nitrous oxide, a greenhouse gas 300 times more powerful than carbon dioxide, has been emitted to the atmosphere.

"Farmers have the power to improve N balance scores," said Alison Eagle, scientist at EDF. "Our research finds that nutrient management and conservation practices have as much or more impact on how much nitrogen leaves a field than external factors like weather do."

EDF scientists published four modules that can be used collectively or separately, as needed:  

1. Why N balance is a robust and practical way to measure excess nitrogen. This module summarizes the scientific consensus that N balance is the preferred metric for measuring nitrogen losses.
2. How to calculate N balance. This module explains how to calculate N balance scores under multiple crop and nutrient scenarios, including whether cover crops are used and whether a farmer uses synthetic fertilizer or manure.
3. What the N balance safe zone means. This module explains how to understand N balance scores using the concept of the safe zone — a range of N balance scores that indicate the range in which a farmer is optimizing yields, minimizing excess nutrients and protecting long-term soil health.
4. How to use N balance to estimate nitrous oxide and nitrate losses. This module explains how to aggregate N balance scores from at least 300 fields and apply EDF's environmental models to calculate nitrogen losses to the air and water.

Visit edf.org/n-visible to download these resources and access the peer-reviewed research that informed them.