Cal. LAB § 1155.2

(a) For purposes of this part, to bargain collectively in good faith is the performance of the mutual obligation of the agricultural employer and the representative of the agricultural employees to meet at reasonable times and confer in good faith with respect to wages, hours, and other terms and conditions of employment, or the negotiation of an agreement, or any questions arising thereunder, and the execution of a written contract incorporating any agreement reached if requested by either party, but such obligation does not compel either party to agree to a proposal or require the making of a concession.

(b) Upon the filing by any person of a petition not earlier than the 90th day nor later than the 60th day preceding the expiration of the 12-month period following initial certification, the board shall determine whether an employer has bargained in good faith with the currently certified labor organization. If the board finds that the employer has not bargained in good faith, it may extend the certification for up to one additional year, effective immediately upon the expiration of the previous 12-month period following initial certification.