Panel: A minus R remains practical for grower reporting; models recommended for regional interpretation

Nov 21, 2025

The State Water Resources Control Board’s agricultural expert panel on Nov. 19 said A minus R is a pragmatic metric for grower-level reporting but recommended hydrogeologic and SWAT-style models be used by coalitions or regions to interpret and set targets for groundwater protection.

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The State Water Resources Control Board’s second statewide agricultural expert panel concluded Nov. 19 that A minus R (applied nitrogen minus nitrogen removed) is an appropriate, practical metric for growers to report and for regulators to compare performance at the field level, while hydrogeological models (including CV SWAT used in the Central Valley) should inform regional targets and long-term groundwater impacts.

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