Contribution to the HiStory Series in Plant Nutrition: Nitrogen Issues in the 19th Century: II What Is Special About Legumes in Terms of Their Nitrogen Nutrition?

After Justus von Liebig had largely recognized the necessity of nitrogen fertilization to achieve high yields from 1862 onwards, the question of why legumes are particularly beneficial for crop rotation remained unanswered. Schultz-Lupitz (1831–1899), who convincingly proved the preceding crop effect of legumes for cereals as a subsequent crop in his fertilization system, assumed that legumes, in contrast to cereals, can absorb nitrogen from deeper soil layers. The debate led to numerous experiments, ultimately leading to the discovery by Hermann Hellriegel (1831–1985) that legumes can fix atmospheric nitrogen with the help of nodule bacteria. He conducted comparative container experiments with legumes and cereals under sterile and non-sterile conditions with soil extracts. This represented a scientific breakthrough, which Hellriegel presented for the first time in 1886 at the meeting of the Gesellschaft Deutscher Naturforscher und Aerzte (Society of German Naturalists and Physicians) in Berlin and published in detail together with Wilfarth in 1888. This scientifically substantiated the practical value of legumes in crop rotations, which was already empirical knowledge of Roman agricultural authors.