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
Safe Drinking Water Act radium and uranium. EPA proposed regulations for radon in 1991 and 1999. Secondary drinking water standards are non-regulatory guidelines for aesthetic characteristics, including taste, color, and odor. EPA issues "health advisories" for some contaminants; some of which have not been regulated with MCLs. Health advisories provide technical information to public health officials about health effects, methods for chemical analysis, and treatment methods. The advisories are not enforceable. However, they were codified in the Safe Water Drinking Act amendments of 1996. As of 2017, health advisories have been issued for the following contaminants. The SDWA requires EPA to identify and list