Fertilizer adoption is persistently low among Sub-Saharan African farmers. Numerous governments have responded by introducing substantial price subsidies, but solving an allocation problem by introducing price distortions has unclear welfare implications. This paper presents results from a theory-guided experiment on fertilizer adoption among Ugandan farmers, finding that there exists a group of farmers with high returns to fertilizer, who would not adopt at the market price but can be induced to adopt with a 30% subsidy. Furthermore, consistent with adoption frictions due to liquidity constraints, the results indicate that a cash transfer is sufficient to eliminate the need for subsidies. These findings tie into broader ideas on second-best policymaking (Lipsey and Lancaster, 1956) and have important implications for fertilizer policy in Africa.