This book includes the results of an investigation of the use of waste pyrite as an alternative to gypsum for alkali soil amelioration. Tailings from sulfide mines usually contain large amount of pyrite (FeS2), which is a potential pollutant. Therefore, waste pyrite must be disposed off under strictly controlled conditions. On the other hand, pyrite may be a remediation additive for alkali soils to increase the availability of essential micronutrients for plant growth and thus increase the dry matter yield; and to adjust the pH and/or soil chemistry because of its acid generating capacity. This book presents that pyritic tailings from a copper concentration plant can be effectively used in alkali soil amelioration with no deleterious heavy metal contamination.