Niter Production

Nitrated Soil is gathered from Niter Bedding via right-clicking with a shovel, after an efflorescence has accumulated on the block. Efflorescence can accumulate on Niter Bedding by having farm animals on top of the bedding for an extended period of time (around 2-3 in-game days, though the accumulation is random and increases in speed the more animals you have).

After you get the nitrated soil, you can brew them as a potion ingredient in a brewing stand, with bottles of water as the potion base. This will give you Bottles of Liquid Niter that can be used to fill a Cauldron. When you place a heat source, such as lava, a camp fire, or fire, directly under a Cauldron of Liquid Niter, the liquid will crystallize over time to produce Niter.