In the most intensively cultivated land in Europe—the Marais district of Paris—owners of small city-garden plots applied dung at rates as high as hundreds of tons per acre, and every year they had to repeat the process. By 1700 or so, hungry Europeans were experimenting with other soil additives in an attempt to increase their yields, trying sea salt, powdered limestone, burned bones, rotting fish, anything that might keep their soils producing.
