Term for the practice in agriculture of compensating for a deficiency in the soil by supplying nutrients of a mineral and organic nature. The name is derived from "dung" (excrement of herbivores, especially ungulates). This oldest form of fertilizer was used as early as six millennia ago. Targeted fertilisation began in the 18th century with wood ash, lime and marl. Around 1840, the German chemist Justus Liebig (1803-1873) proved the growth-promoting effect of potassium, phosphorus and nitrogen. He wrote in his Haptwerk "Organic Chemistry in its Application to Agriculture and Physiology": The soil must fully recover what is taken from it by harvesting.