This study presents an incentive scheme to control agricultural nonpoint-source pollution. The analysis is based on a principal-agent framework with two parties: farmers and a regulating authority. Our incentive scheme proposes collective penalties as a way to control pollution. Unlike previous analyses of incentive schemes to control agricultural pollution, we suggest nonindividual contracts between farmers and a regulating authority, where farmers can trade pollution abatement efforts. Findings show that the information requirement of a regulatory agency can be substantially reduced if contracts can be made nonindividual.