This article discusses the production side of nutrient pollution from agricultural sources, given that farmers' nutrient management practices and environmental discharges cannot be directly monitored and regulated or taxed. Do unpriced environmental impacts of farmers' fertilizer decisions lead to ‘overfertilization’? If so, what is the source of the incentive for overfertilization and how can it be corrected? Two types of farmers are considered: (1) crop farmers who choose how, when, and how much commercial fertilizer to apply to their crops and (2) livestock facility operators who manage the manure waste from their livestock, including treatment regimens and applications to surrounding croplands. This article describes how ‘overfertilization’ can arise despite fixed coefficient (von-Liebig) production technologies that might be expected to produce fixed fertilizer applications to farmlands. Farmer choices on timing and rates of fertilizer application, between organic and chemical fertilizers, and on livestock manure disposal on farmlands proximate to confined animal production facilities, all yield private economic trade-offs and ignored environmental effects that can motivate government price interventions in fertilizer markets (such as chemical fertilizer taxes) and regulation of observable practices that affect nutrient discharges (such as irrigation and waste treatment technologies).