I have no knowledge of farming in Europe before the use of modern day fertilizers. I doubt if all farms were productive, especially if the King or Lord claimed all the "droppings"!
Remember that this country was very sparsely settled for many years. Few "roads", newspapers, or letters, and definitely no TV... Many of the people who came here were unable to see a future in Europe. They may have been farmers or sharecroppers on land that was no longer productive.
Some were criminals (per the laws and customs common then), and were banned to the colonies. Many were bound to someone, essentially slaves. When possible, they got away. If lucky, they earned their "freedom" and were given enough money or had learned a trade, so were able to go where land was cheap and survive.
Some were soldiers, who decided to stay. Many probably thought they could farm, but did not have the knowledge to do it productively. 50 years ago my father chuckled about new neighbors who had worked "in the cities", made some money, and decided to move to our rural area and farm. Many of the ones who had not grown up on a farm eventually lost their farm. They did not know how to repair their equipment, when to plant or harvest, what to use to kill insects, what to feed or not feed their animals or "birds", how to kill lice, etc. And, they borrowed a lot of money to buy the land, cattle, and equipment, then could not earn enough to pay off their loans.
A lot of the people who moved west to new lands went as loggers, hunters, and traders. They did not have a history and knowledge of farming. They were not educated, many (most?) could not read or write.
Is it any wonder that many did not become wealthy as farmers?
Remember the stories about the cattle ranchers hating the sheep raisers? The sheep chewed off the grass so short that a lot of it died, and cattle on the same range would starve.
Rotating crops is a waste of time if the soil improving crops like alfalfa will not grow because there is no calcium left in the soil. A few people in some areas had lime deposits available close enough so that they could afford to transport and spread it by hand. And some knew enough to do it. Today we have agricultural agents and other sources for soil testing. When I was a young boy, that was not readily available, and farmers decided what their soil needed by looking at how the plants and weeds grew, the color of their leaves, and what plants and weeds would or would not grow.
There were groups of people and individuals who were knowledgeable farmers in Europe, who came here for religious freedom, or simply because they had heard of how well crops grew here. If they settled on good soil, had adequate rain and no floods, were not killed by Indians or the English or French or their neighbors, were not killed in a forest fire, did not die from disease or starvation, and their land was desirable because it was near a waterway or road used for commerce, or near a growing town or city, they had a chance of having a good life.
I worked with a Ukrainian many years ago, whose family made their own charcoal, and collected the distillates like our oil refineries do, made wine, and made essentially everything they needed. Few of the early settlers of this country had the knowledge to do that. Many did make their own soap, some made beer and wine. Some knew how to tan hides and make leather, or learned from the Indians. Remember the stories about the Indians burying a fish (fertilizer) in each hill of corn or other crop they planted? That was copied by some of the early settlers who lived near lakes and rivers.
Many of the "homes" in the early 1850 time periods in the area I grew up in Michigan, were only about 10 by 14 feet, with board or thatch or sod roofs. Nails were often not available, or were not affordable. In some areas, most of the new settlers lived in homes made by building a "lean-to" or roof and three sides against a hillside. And remember, they did not have birth control. Many families had 8-14 children. And took in the neighbors whose house burned, or new neighbors who were building a house. Eventually, the successful farmers, loggers, businessman, and others, built better and better homes.
And we complain because we can not find birth, marriage, and death records for all our ancestors