Panel debates three nitrogen-accounting 'pathways'; members push to simplify technical targets

Panel experts spent a substantial portion of the meeting parsing the technical mechanics of three compliance pathways proposed for calculating irrigation‑derived nitrogen and how those choices would change growers' allowable fertilizer inputs.

Michael Cohen summarized the issue: the three pathways differ in whether and how much irrigation‑water nitrogen (AIR) is included in the a‑minus‑r equation that defines allowable fertilizer application. He illustrated multiple scenarios showing that which pathway favors growers depends on irrigation N concentration, crop evapotranspiration and the numeric target. "I just wanted to point out that there is some, you know, problems with having these 3 pathways when you get to the lower targets," Cohen said, arguing the structure can be confusing for implementation.

Panelists discussed practical complications: how to credit irrigation water when water is applied before crop establishment, the role of leaching fraction and mixed water sources, and whether regional programs (e.g., Central Valley) perform fuller accounting. Thomas noted ambiguity in the draft language for pathway 2 and recommended it read as a "less or equal" condition rather than an exact equality, a clarification others supported.

Using worked examples, Cohen showed that capping credited irrigation N at 200 lb/acre (a cap used in prior regional Ag Order 4 language) can produce simpler outcomes in most scenarios, and he proposed consolidating to a single pathway with an upper credit cap to avoid inconsistent incentives across regions.

Panelists tasked Richard Smith and Hannah Waterhouse (with input from Michael Cohen) to revise the draft response to Question 7d to make the pathways clearer, correct noted typographical or logical errors (e.g., inequality signs), and present a cleaned-up version at the next meeting.