Long ago, barnyard manure was adequate for all garden needs. Pig manure (aged) was the best, followed by horse and cow manure. Chicken manure was good but it had to be stored for a longer time.
My father kept animals - cows, pigs, horses, chickens, and sheep. A multi-level barn kept all animals happy and dry. From the age of 13 to 18 my chore was to clean it twice a week. My companion was a shovel. Shovel it to the edge of the second level, throw it on the pick up, drive the pick up to the storing area, and unload it by hand. Then, pick up fresh sawdust, load it by hand, and unload it in the barn. The cycle kept repeating itself. It definitely gave me muscles.
I hauled the finish product to the nursery too. We sold 2 cubic bags, 3 for a dollar. We would fill bags of manure by the hundreds. People loved it.
Fast forward to present day. No more barnyard manure - it stinks and attracts flies. People can't stand smell. Stores have packaged fertilizers. They smell sweet - the odors must come from France. Packages are done up in vibrant colors - loud pink, green, yellow, etc. You can see the package from a mile away.
Today, a PhD qualified master mixes a special blend for your sun, shade, morning, noon - whatever condition has a special blend. Like the coffee mixes. Only a PhD can find the minute elements of zinc, gold, or fuchsia to go along with your condition. Just remember to wash your hands when you're done.