Fertilizing Crops is Ancient

From Science:

Europe's first farmers helped spread a revolutionary way of living across the continent. They also spread something else. A new study reveals that these early agriculturalists were fertilizing their crops with manure 8000 years ago, thousands of years earlier than previously thought.

Fertilizer provides plants with all sorts of nutrients that they need to grow strong and healthy, including, most importantly, nitrogen, phosphorus, and potassium. That's why farmers all over the world, in countries rich and poor, put manure on their crops. Nevertheless, it may not be intuitively obvious that spreading animal dung around plants is good for them, and archaeologists had found no evidence for the practice earlier than about 3000 years ago. Farmers in the Near East—what is today Israel, Palestine, Syria, Jordan, and neighboring countries—began cultivating plants and herding animals about 8000 B.C.E., but there are no signs that they used animal dung for anything other than as fuel for fires.

So a team led by Amy Bogaard, an archaeobotanist at the University of Oxford in the United Kingdom, decided to look for evidence in Europe, where farming began to spread from the Near East about 8500 years ago. Manure has a higher than normal proportion of the rare isotope nitrogen-15, which is heavier than the more common N-14. The researchers took advantage of recent agricultural research showing that plants treated with manure also have more nitrogen-15. They measured the nitrogen-15 content of plant remains from cereals such as wheat and barley and pulses such as peas and lentils from 13 early farming sites. The sites dated to between 7900 and 4400 years ago and ranged from Greece and Bulgaria in the southeast to the United Kingdom and Denmark in the northwest. As the team reports online today in the Proceedings of the National Academy of Sciences, the nitrogen-15 levels in 124 crop samples, totaling more than 2500 individual cereal grains or pulse seeds, were high and consistent with the use of manure at most of the 13 sites.

This makes a pretty good case. I have no trouble imagining how this happened -- some seeds fell in a manure pile and grew much taller than the other plants, and somebody said, hmmm. Original article here.