New Delhi, Aug. 14 -- The partnership between the world's two largest democracies has repeatedly stumbled on one issue: agricultural market access. Trump wants India to open its doors to American farm products-from dairy, poultry and maize to apples, almonds and genetically modified crops. India resisted, wary of destabilizing its rural economy. This defiance is economically prudent and socially necessary. But shielding farmers from unfair competition is only half the battle. Without structural reform, Indian agriculture will remain inefficient and fiscally draining, slowing and even strangling our economic transformation.

The US spends billions annually to prop up its agricultural sector through direct payments, crop insurance subsidies...