It was a late harvest in fall 2018. Soils were wet and frozen when it was time to apply anhydrous ammonia. Those situations resulted in much less than normal anhydrous ammonia application last fall. Therefore, considerable anhydrous ammonia needs to be applied this spring. There is only so much capacity to switch from one nitrogen (N) fertilizer product to another. In Iowa, historically the two largest N fertilizers are anhydrous ammonia (largest) and urea-ammonium nitrate (UAN) solution, with granulated urea a distant third.