Ammonia (NH₃) volatilization from NH₃-based fertilizer and animal manure reduces their nitrogen (N) fertilizer value and is a source of environmental pollution. Mixing manure with biochar may lower NH₃ volatilization from manure by adding H⁺, adsorbing mineral N, or increasing N immobilization in microbial biomass. The objective of this study was to determine whether wood-based biochar could lower NH₃ volatilization from vented pails containing manure (liquid swine, dairy slurry, and solid poultry manure) or a urea ammonium nitrate solution (UAN). Two types of wood-based biochar (BlueLeaf and Dynamotive) were mixed with three types of manure and UAN fertilizer solution at 0, 2.5, 5, 10, and 25% biochar by volume in vented pails. After 21 d storage in an outdoor shaded area, the greatest NH₃ volatilization was from poultry manure, which had pH 9.4 on average and low water content regardless of the biochar source and application rate. There was less NH₃ volatilization from UAN fertilizer solution when mixed with 25% (v/v) of Dynamotive biochar compared with NH₃ volatilization from UAN fertilizer solution mixed with 0%–10% (%) of Dynamotive biochar, probably because pH decreased from 7.0 to 6.4 after 21 d contact. Mixing wood-based biochar with manure had no impact on NH₃ volatilization, suggesting that these biochar sources did not appreciably change the pH and N dynamics in stored manure after 21 d.