Fibrous sphagnum peats are good, but more expensive than compost or manure. Don't use dusty, fine peats that clog soil drainage. Native Colorado mountain peat is generally inferior as a soil amendment, and its harvest destroys mountain wetlands and stream systems. The best peats come from the northern states and Canada. Manures should be aged for at least one year and composted if being used on fruits and vegetables.
Fresh manure is too high in ammonia and burns plant roots.
Avoid feedlot manures which are typically high in salts. Dairy cattle manure is generally a better quality, but poultry manures can also be used. Horse or sheep manures may carry weed seeds, spreading their growth. Compost is perhaps the best organic amendment. It can be purchased or made at home by recycling yard prunings and clippings.