Crop rotation British Agricultural Revolution. The rotation between arable and ley is sometimes called ley farming. George Washington Carver (1860s–1943) studied crop-rotation methods in the United States, teaching southern farmers to rotate soil-depleting crops like cotton with soil-enriching crops like peanuts and peas. In the Green Revolution of the mid-20th century the traditional practice of crop rotation gave way in some parts of the world to the practice of supplementing the chemical inputs to the soil through topdressing with fertilizers, adding (for example) ammonium nitrate or urea and restoring soil pH with lime. Such practices aimed to increase yields, to prepare soil
History of municipal treatment of drinking water clean water from outside the city. The New River was slow flowing, which helped to increase sedimentation. It also had screens installed every few miles to catch any debris and weeds. These screens required periodic maintenance and workmen were employed to clean them and cut back the weeds. The new river would meet London's needs well enough that there were few complaints before the 19th century, although the water supplied was rarely used for drinking directly, rather it was more likely used for washing or the brewing of beer. By the beginning of the 19th century filtration became a means