Term for the practice in agriculture, by supply of nutrients mineral and organic nature a shortage in ground compensate. The name derives from "dung" (excrement of herbivores, especially ungulates). This oldest form of fertilizer was used at least six millennia ago. Targeted fertilization began in the 18th century with wood ash, lime and marl. Around the year 1840, the German chemist Justus Liebig (1803-1873) demonstrated the growth-promoting effects of potassium, phosphorus and nitrogen. He wrote in his main work "Organic Chemistry in its Application to Agriculture and physiology ": The soil must be fully recovered, what it is taken by harvesting.