The importance of biological fixation of atmospheric nitrogen by leguminous crops

Abstract Biological reduction of atmospheric nitrogen (BNF) is one of the most important biological processes on earth with great economic as well as ecological significance. The unique ability to convert non-reactive nitrogen into plant-available ammonia is possessed only by archaeons and bacteria belonging to the diazotrophs. Legumes are a valuable component of crop rotation and their cultivation brings many benefits. However, the most important and invaluable feature of this group of plants is their ability to fix molecular nitrogen in symbiosis with root nodule bacteria. Higher organisms remaining in symbiotic systems are able to fix approximately 200–500 kg N ha −1 year −1 . In contrast, non-symbiotic bacteria fix considerably less nitrogen (1–50 kg N ha −1 year −1 ). This element, while remaining in crop residues, can be utilised by succeeding plants in the crop rotation. This is particularly important because of the possibility of reducing the use of mineral fertilisers by up to 20–25%. Thus, the importance of legumes in crop rotation is of particular importance in both organic and integrated crop production. The aim of this study is to systematise knowledge on the importance of legumes in crop rotation, the symbiosis of legumes with symbiotic bacteria of the genus Rhizobium , the impact of factors interfering with this process and newly recognised methods to support it.