Nitrogen (N) is essential for high crop yields to feed a growing population, but excess nitrogen contributes to climate change as nitrous oxide and to water pollution as nitrate.
Historically, measuring nitrogen losses has been expensive and time consuming. Environmental Defense Fund’s N-Visible framework remedies that.
N-Visible provides an easy-to-use, scientifically robust way for farmers and their advisers to assess nitrogen losses from individual fields. It also allows food companies and policymakers who promote on-farm sustainability to measure progress toward improved environmental outcomes at regional scales.
An open-source implementation guide is now available for download. Here’s what it contains and how to use it.
1. Why N balance is a powerful metric
There is clear scientific consensus that N balance — the difference between the amount of nitrogen applied to a field and the amount removed at harvest — is a strong proxy for nitrogen at risk of being lost to the environment.
Module one [PDF] synthesizes published research from scientists at land-grant universities, EDF and other institutions that finds a consistent and durable link between N balance and nitrogen losses. It also explains why N balance is easier to use and scale than existing methods of measuring and monitoring excess nitrogen.
2. How to calculate N balance
Module two [PDF] provides a step-by-step guide for calculating N balance scores under a variety of crops and growing practices, including when soybeans or cover crops are part of the rotation and whether nutrients come from legumes, manure or synthetic fertilizer.
It also explains the data inputs needed, as well as the scientific rationale for them and the underlying assumptions made.
3. How to interpret N balance scores
Module three [PDF] explains that if N balance scores fall within a scientifically determined “safe zone,” a farmer is optimizing yields, using nitrogen additions efficiently, minimizing nitrogen losses to the environment and protecting long-term soil health. N balance scores below the safe zone may indicate depletion of soil nutrients, and scores above the safe zone indicate greater risk of nitrogen losses to the air and water.
The good news is that producers have the power to control this. A recent peer-reviewed article published by EDF scientists and university colleagues finds that farmer decision-making and production practices can improve N balance scores and reduce the amount of excess nitrogen at risk of becoming climate or water pollution, even in the face of variable growing conditions like weather events. Open-source framework provides an easy-to-use, scientifically robust way to assess nitrogen losses from individual fields and watersheds. Learn more. Click To Tweet
4. How to estimate nitrate leaching and nitrous oxide emissions
Module four [PDF] provides a step-by-step guide for using EDF’s groundbreaking environmental models to measure progress toward climate and water quality goals. The models convert aggregated N balance scores into nitrous oxide emissions and nitrate losses at watershed, regional or national scales. This aggregation protects producer privacy and improves predictive accuracy by including more data points.
The module also provides guidelines for publicly reporting greenhouse gas emission reductions and converting to carbon dioxide equivalents.
The implementation modules above, and the robust science underpinning them, were developed collaboratively with key stakeholders, including growers, crop consultants and scientists, over several years. The N-Visible framework represents a significant advancement in the science of quantifying environmental outcomes from agriculture.
Read the full guide at edf.org/N-Visible