because their diet was better; presumably, more nutrients remained in their excreta. Various historic documents dating from the 9th century detail the disposal procedures for toilet waste. Selling human waste products as fertilizers became much less common after World War II, both for sanitary reasons and because of the proliferation of chemical fertilizers, and less than 1% is used for night soil fertilization. The presence of the United States occupying force, by whom the use of human waste as fertilizer was seen as unhygienic and suspect, was also a contributing factor: "the Occupationaires condemned the practice, and tried to prevent their compatriots from eating vegetables and fruit from the local markets". Mexico and Central America Various Mesoamerican civilizations used human feces to fertilize their crops. The Aztecs, in particular, are well known for their famous chinampas, artificial islands made of mud and human waste used to grow crops that could be harvested up to seven times a year. Current research has placed the origins of chinampas in an Aztec town of Culhuacan in the year 1100 C.E. They were constructed by first fencing an area between 30 m x 2.5 m and 91 m x 9 m, using wattle. Then filled in with mud, sediment, feces and decaying vegetation. To stabilize the chinampas, trees were often planted on the corners, primarily āhuexōtl (Salix bonplandiana) or āhuēhuētl (Taxodium mucronatum). Chinampas were very common before Spanish conquest and are still found in Mexico today. United Kingdom In Britain during the Medieval period, it was not uncommon for human feces to be spread on farms for use as fertilizer. A gong farmer was the term used in Tudor England for a person employed to remove human excrement from privies and cesspits. Gong farmers were only allowed to work at night and the waste they collected had to be taken outside the city or town boundaries. The rapid industrialisation of England during the 19th century led to mass urbanisation, over-crowding, and epidemics. One response was the development of the "Rochdale system", in which the town council arranged for the collection of night soil from outhouses attached to each dwelling or group of dwellings (see pail closet). A later response was the passage of the Public Health Act 1875, which led to the creation of byelaws regarding housing, mandating one outhouse per house. These were "earth closets" (not water closets i.e. WCs) and depended on