Air quality policies have traditionally focused on urban areas and industrial emissions. Extending these laws to cover agriculture would require an understanding of how farmers respond to different policy incentives. Farmers have many choices in deciding on what to produce and the production practices to use. Environmental policy can influence a farmer's decisions by changing the costs of inputs to encourage or discourage input use, or by mandating that particular management practices be used or abandoned. Currently, a lack of knowledge about air emissions from agriculture could hinder the development of cost-effective policies.