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
Lead contamination in Washington, D.C. drinking water Lead contamination in Washington, D.C. drinking water Lead contamination in Washington, D.C. drinking water, first discovered in 2001, left thousands of children with lifelong health risks, and led to a re-evaluation of the use of chloramine in public drinking-water systems. Professor Marc Edwards, an expert in plumbing corrosion, discovered lead levels at least 83 times higher than the accepted safe limit while performing research into premature pipe corrosion for the District of Columbia Water and Sewer Authority (WASA). He found that the decision to change from chlorine to chloramine as a treatment chemical had caused the spike in lead levels.