Expert panel leans toward area-based nitrogen targets, not crop-specific limits

Dr. Daniel Geisler, chair of the expert panel convened by the State Water Resources Control Board, said the groupwas focused on whether the scientific evidence supports developing numeric limits and how those numbers could be produced and implemented. "The questions aren't asking the panel to necessarily come up with the number," he said, describing the panel's charge as assessing whether and how to get to defensible limits.

Panelists repeatedly raised practical challenges with crop-specific numeric limits and urged an area‑based approach measured over time. "There's no crop‑specific nitrogen limit that makes sense in this context," said Thomas (panelist), advocating for place‑based accounting units (he suggested 40 to 160 acres as a reasonable minimum) and per‑year or multi‑year rolling averages to capture rotations and cover crops. Several participants noted the Central Valley and coastal cropping systems differ enough that a single one‑size‑fits‑all number would be inappropriate.

Several panelists framed the discussion in terms of the A-minus-R accounting concept used in existing ag orders: "A minus R is a good tool," one panelist said, but it must be adjusted to account for cover‑crop scavenging, organic amendment availability and regional soil and climate differences. Panelists said modeling tools such as CV‑SWAT and coalition analyses can translate growers' reported A and R inputs into estimated leaching risks at a landscape scale.

Panelists emphasized process and feasibility. Richard (panelist) urged distinguishing between "targets" and enforceable "limits," recommending the panel prioritize recommendations on methodology, monitoring and incentives that would let regions adopt feasible targets over time. "If growers are constrained by a sandy soil," Ali (panelist) observed, the policy must provide fair ways to account for varying risk while encouraging mitigation practices such as cover crops and irrigation improvements.

The panel asked staff for clearer definitions of "targets" versus "limits" at the Oct. 31 meeting and agreed to compile region‑specific methodologies. The group also agreed to a drafting process: two‑person teams will prepare draft language for each question so the panel can review and iterate in live sessions.

What happens next: staff will present definitions and modeling options at the Oct. 31 panel meeting; the panel plans to produce a draft report for a 30‑day public comment period before a final plenary.

Attribution: Quotations and attributions in this article come from panel members and staff speaking at the public working group session and are drawn from the meeting transcript provided to the panel.