An expert panel convened by the State Water Resources Control Board spent most of its meeting debating how regulators should measure and manage nitrogen applied to cropland, the geographic and temporal scale appropriate for targets, and which monitoring and modeling tools should inform regulatory decisions. Panelists emphasized regional differences, the importance of on-farm testing and education, and the need for phased, evidence-based recommendations.

Panel chair President Daniel Geisler opened by stressing the panel’s charge: “estamos en sí en espera de sus recomendaciones por su experiencia técnica.” The discussion ranged from a proposal to express targets as pounds per acre per year to recommendations that targets be based on area units (for example, 40- or 160-acre assessment units) and multi-year averages. Panelists repeatedly said a single statewide number would not fit all regions.

Why this matters: groundwater contamination by nitrate is a public-health concern in many California regions. The panel’s guidance will be used by the State Water Resources Control Board and regional coalitions as they refine Agricultural Order implementation and monitoring programs.

Panelists debated indicator choice and scale. Several speakers argued the preferred metric should be an annual “A minus R” (applied nitrogen minus nitrogen removed) calculated for a place-based unit (field, farm, or aggregated assessment area) rather than per-crop limits. Tomás and others proposed using an area-based unit (40–160 acres was discussed) and a moving average (three years was suggested) so variability between seasons and crop rotations is reflected.

Proponents of area-based, multi-year metrics said those approaches better reflect hydrology and farming realities in regions with multiple crops per year or complex rotations. As one panelist summarized, a per-crop limit “no es específico de una cosecha” and may miss seasonal and rotation effects.

Monitoring, sampling and agronomy: soil nitrate testing and frequent in-field measurement were highlighted as essential complements to any metric. Eric Morgan of the soil health lab described the laboratory and sampling protocol his team uses (multiple cores, depths into the top two feet, standard UC sampling procedures) and recommended thresholds that would prompt reduced fertilizer application. He said, “si hay 200 libras presente en esos 2 pies superiores ... mi consejo para un cultivador sería no aplicar más nitrógeno.” Morgan and other technical speakers described how mineralization, irrigation water nitrate, cover crops and crop residues complicate simple per-crop accounting and argued for including those factors when producing agronomic guidance.

Modeling and tools: panelists discussed use of more complex process-based models (for example, CV-SWAT and regionally used tools such as CropManage) to translate field reports into estimates of leaching risk. Several speakers urged the panel to recommend a menu of methods—simpler mass-balance accounting (A minus R) for some uses and modeling for groundwater-impact assessments—rather than a single tool for all regions.

Regional differences and exceptions: participants repeatedly noted key regional differences (Central Valley, Salinas/Salinas Valley, Imperial Valley, desert regions and coastal central areas) that affect risk and practicability of particular interventions. Nursery operations, container production and operations with impermeable surfaces were identified as scenarios where measurement of discharge might be more appropriate than A-minus-R accounting.

Education, incentives and technology: panelists emphasized that outreach, farmer training and incentives will be necessary for producers to change practices. The group discussed cover crops, improved soil health, precision fertilizer technologies and inhibitors as tools to reduce leaching. Several panelists said education alone is unlikely to produce uniform change without additional incentives or support programs.

Process and next steps: the panel agreed to form small writing teams (two people per question) to draft responses to the panel’s charge questions and to circulate drafts for discussion. Staff asked for a draft timeline and indicated the panel should aim to have a draft for public review around mid-January, followed by a 30-day public comment period. The panel scheduled a larger informational session on Oct. 31 (presentations from CDFA and modelers were mentioned) and additional working sessions in November–January to complete the draft.

Ending: Panelists asked staff to arrange presentations comparing Valley and coastal modeling approaches, and several speakers said the panel should return to revisit recommendations as new technologies and data become available.