The environmental costs of fertilizer use in the tropics are understudied. Mato Grosso, Brazil, once an Amazon deforestation hot spot, is expanding Nitrogen fertilizer use for maize production. Fertilizer use can cause NO gas loss (which drives smog and ozone production), and release N₂O (a potent greenhouse gas). We will measure these gases at a large commercial farm in Mato Grosso to inform policy in the Amazon region and tropical agriculture.