Agriculture has recently been noted as a provider of non-market environmental benefits in addition to its traditional recognition as a source of negative externalities from polluting inputs. In this paper, a general equilibrium framework is used to determine optimal land subsidies and input taxes in agriculture. When agriculture generates both amenities and pollution, the optimal subsidy does not equal the net extra-market value of agricultural land. If opened to international trade, a small economy will fully correct externalities, while large economies have an incentive to set policies at non-internalizing levels to exploit terms-of-trade effects.