Back around 10,000 BC, people started to farm. They started growing food where they were living and keeping animals with them to help with the work. Back then the soil had not been over farmed yet and people did not really need fertilizers to farm. Then, around 8,000 years ago in Europe, some farmer must have been walking his fields and seen a greener spot of grass. This must have made him curious. After seeing this happen multiple times, he probably noticed this was happening where he was keeping his cows. Next, this farmer must have realized it was the manure that was making his grass green. From then on, people started to use the manure from their farm animals to fertilize their crops. The reason these early Europeans started to use manure to fertilize was because they started keeping the same farm fields for long periods of time, and the nutrients in the soil started to run out. When these early Europeans started to fertilize with manure, they could use the same fields for longer and grow better crops for their families. After the Europeans started to use manure to fertilize, the practice of using manure spread around to other ancient cities. Over time this use was also modified.
One of the first modifications of manure as a fertilizer happened in Egypt. When Egyptians started using manure to fertilize, they realized that when they burned the weeds in their fields after laying down manure their crops grew healthier. From then on the Egyptians burned weeds and mixed the burnt weeds in with manure before spreading it on their field. The Egyptians were not the only people to modify manure. When manure's fertilizing qualities were discovered in populations living by a sea shore, these people added sea shells to the manure. Sea shells have phosphorus in them, which is a mineral that helps plants grow. Therefore, by adding sea shells to manure, its fertilizing quality was strengthened and plants grew even healthier.
Over the next few thousand years, people started to use manure from different animals besides cows. People discovered that chicken manure was easier to keep and did just fine as manure. The only problem with chicken manure was that chickens don't poop as much as cows. Next, people discovered that dog manure grew super healthy plants. This was because dogs spend all day eating bones, which are full of phosphorus. When using dog manure, people did not need to add sea shells to their manure. The use of manure got so crazy that people actually fought over an island off of Peru that was buried 25 feet deep in bat guano. Farms all over the world were thriving with their manure fertilizer, and they were not only helping their plants grow, but also helping enrich the soil. Then, after thousands of years of using manure as fertilizer, Fritz Haber came along and invented chemical fertilizer in 1908. From then on only a few people still used manure. Now farmers use chemical fertilizers and have dried our lands and almost completely stopped using manure.
Just in the past few years, some farmers have been smart with their manure. For example, some farmers are buying up to 8,000 acres in land for cattle. Most of these cattle farms are only breaking even. So why do farmers do it? They do it for the money. With 8,000 acres worth of cows, a lot of manure will be created. Not only do these farmers then sell this manure for more money, but they also can save some for themselves to use as fertilizers on their own farms.