Manure-based soil amendments (MBSAs) must be managed optimally to maximize N concentration and availability while minimizing environmental impacts (e.g., greenhouse gas [GHG]) emissions. We conducted an 83-d incubation study to determine the effects of different moisture (60 or 120% of water-holding capacity [WHC]) and temperature (4 or 20°C) conditions during the decomposition of MBSAs. We measured CO, CH, and NO emissions and total C, total N, NH, and NO during the decomposition of chicken MBSA and two understudied MBSAs (turkey and horse). Total N decreased by 38 to 50% after 83 d in poultry MBSAs incubated at 20°C and 120% WHC, whereas NH concentration peaked at 30 d. In contrast, poultry MBSAs incubated at 60% WHC or 4°C had limited N losses but higher CO and/or NO emissions. Horse MBSA incubated for 83 d at 20°C and 60% WHC had two- to threefold higher C losses, 53 to 68% higher total N, and two to three orders of magnitude higher NO concentrations than at wetter and/or colder incubation conditions. Horse MBSA incubated at 20°C and 60% WHC had 13- to 130-fold (CH) and 4- to 70-fold (NO) higher emissions than horse MBSA incubated at 4°C. In contrast, CH emissions peaked at 120% WHC and 20°C. Overall, incubating horse MBSA at 20°C and 60% WHC minimized tradeoffs between maximizing N concentration and availability and minimizing GHG emissions during decomposition, whereas we found no ideal decomposition conditions for poultry MBSAs.