The paper examines the issue of designing and implementing policy measures to control complex agricultural externalities. Complex externalities refer to the situation where a production (firm on firm) externality coexists with a detrimental (firm on society) externality. The paper identifies the optimal solution for complex externalities, which is a combination of spatially differentiated taxes. However, severe information requirements render the first-best policy infeasible. Finally, a likely voluntary scheme based on firm self-report is examined which may enforce firm compliance with the optimal policy.