N2-Fixierleistung und N-Flächenbilanzsaldo beim Anbau von Luzerne, Rotklee und Persischem Klee

Summary

Atmospheric N2 fixation by lucerne (Medicago sativa), red clover (Trifolium pratense) and Persian clover (Trifolium resupinatum) were determined in a field study carried out from 1999 to 2000 at three different sites in Lower Saxony, Germany. Simplified nitrogen balance (nitrogen fixed symbiotically in shoots, stubble and roots minus the nitrogen in herbage yield) was calculated using nitrogen data from field studies. Three varieties each of lucerne and red clover, as well as two varieties of Persian clover, were cultivated in pure stands. The forage yield was removed from field plots after each cutting (three or four cuttings per year). The level of symbiotically fixed nitrogen (determined with natural 15N abundance method) which was accumulated in the shoots and roots of lucerne ranged from 20 to 455 kg ha 1 a 1. Nitrogen fixed by red clover varied between 149 and 442 kg ha 1 a 1. Persian clover as an annual crop accumulated between 42 and 177 kg N ha 1 a 1 from the atmosphere. Calculated nitrogen balances ranged from 69 kg N ha 1 a 1 (Persian clover) to +43 kg N ha 1 a 1 (Lucerne). A close correlation was found between the annual herbage dry matter yield and the accumulated nitrogen in the shoots and roots. Our data could be used for calculating tables which represent the expected simplified nitrogen balances in cultivated forage legumes.