The history of agricultural science is a sub-field of the history of agriculture which looks at the scientific advancement of techniques and understanding of agriculture. Early study of organic production in botanical gardens was continued in with agricultural experiment stations in several countries. Fertilizer is a major contribution to agriculture history increasing the fertility of the soil and minimizing nutrient loss. Scientific study of fertilizer was advanced significantly in 1840 with the publication Die organische Chemie in ihrer Anwendung auf Agrikulturchemie und Physiologie (Organic Chemistry in Its Applications to Agriculture and Physiology) by Justus von Liebig. One of Liebig's advances in agricultural science was the discovery of nitrogen as an essential plant nutrient. Fertilizer The first method of soil nourishment utilized compost. Composting used rotten organic materials to replenish the soil of its nutrients and dates back to tenth and twelfth century Arab writings. Composting was a normal and widely used practice of fertilization, up into the twentieth century. Johann Friedrich Mayer was the first scientist to publish experiments on the use of gypsum as a fertilizer, but the mechanism that made it function as a fertilizer was contested by his contemporaries. Agricultural science developed when analytical chemistry began to address organic compounds. Fertilization with decomposed plants sometimes gave a whiff of ammonia, which suggested a role for nitrogen in biological growth. Gerardus Mulder tried to determine the chemical formula for albumin and similar biological substances, but Justus von Liebig is usually cited as the early visionary of protein structure. For instance, he assigned his student Eben Horsford the task of comparing the nitrogen content of grains. More significantly, Liebig analysed biological growth as constrained by limiting factors such as a shortage of phosphorus, potassium or nitrogen. His view is called Liebig's law of the minimum. As the nineteenth century progressed so did soil science and its promulgation by farm journals such as those published by Luther Tucker. The production of synthetic ammonia was acquired by Fritz Haber and Carl Bosh. Haber discovered the reaction process to produce ammonia and Bosh was able to pressurize it to complete the process. Together Haber and Bosch came up with the Haber-Bosch process that fixated nitrogen to produce ammonia that is used in most fertilizers. In 1918 Fritz Haber received a Nobel prize in Chemistry for the invention of this process. Carl Bosch also received a Nobel Prize in 1918, but for high-pressure