From Wikipedia, the free encyclopedia: Liebig improved organic analysis with the Kaliapparat-- a five-bulb device that used a potassium hydroxide solution to remove the organic combustion product carbon dioxide. He downplayed the role of humus in plant nutrition and discovered that plants feed on nitrogen compounds and carbon dioxide derived from the air, as well as on minerals in the soil. One of his most recognized and far-reaching accomplishments was the invention of nitrogen-based fertilizer.
Liebig believed that nitrogen must be supplied to plant roots in the form of ammonia. Though a practical and commercial failure, his invention of fertilizer recognized the possibility of substituting chemical fertilizers for natural (animal dung, etc.) ones. He also formulated the Law of the Minimum, stating that a plant's development is limited by the one essential mineral that is in the relatively shortest supply, visualized as "Liebig's barrel". This concept is a qualitative version of the principles used to determine the application of fertilizer in modern agriculture.
Liebig's Law of the Minimum, often simply called Liebig's Law or the Law of the Minimum, is a principle developed in agricultural science by Justus von Liebig. It states that growth is controlled not by the total of resources available, but by the scarcest resource. This concept was originally applied to plant or crop growth, where it was found that increasing the amount of plentiful nutrients did not increase plant growth. Only by increasing the amount of the limiting nutrient (the one most scarce in relation to "need") was the growth of a plant or crop improved.
Liebig used the image of a barrel-now called Liebig's barrel-to explain his law. Just as the capacity of a barrel with staves of unequal length is limited by the shortest stave, so a plant's growth is limited by the nutrient in shortest supply.
Liebig's Law has been extended to biological populations. For example, the growth of a biological population may not be limited by the total amount of resources available throughout the year, but by the minimum amount of resources available to that population at the time of year of greatest scarcity. That is, the growth of a population of animals might depend not on how much food is available in summer, but on how much food is available in winter.
The University of Giessen today is officially named after him, "Justus-Liebig-Universität-Giessen". Organic Chemistry in its Application to Agriculture and Physiology (1840), Organic Chemistry in its Application to Physiology and Pathology (1842)
