Methodological aspects of determining nitrogen fixation of different forage legumes

Nitrogen fixed by legumes is the main nitrogen source in organic farming systems. The design of crop rotation is strongly depending on the knowledge of how much nitrogen is fixed by legumes. Also for farm scale budgeting of nitrogen it is essential to know the amount of nitrogen fixed by the single leguminous crops. According to the literature, the determination of nitrogen fixation is expensive, time consuming and bears a lot of methodologica