2146: Methodological aspects of determining nitrogen fixation of different forage legumes [Methodische Aspekte zur Bestimmung der symbiontischen N2-Fixierungsleistung verschiedener Futterleguminosen]

Loges, Ralf; Ingwersen, Kathrin; Kaske, Axel and Taube, Friedhelm (2000) Methodological aspects of determining nitrogen fixation of different forage legumes [Methodische Aspekte zur Bestimmung der symbiontischen N2-Fixierungsleistung verschiedener Futterleguminosen]. Paper presented at 13th International IFOAM Scientific Conference - IFOAM 2000 - The World Grows Organic, CH-Basel, 28.-30. August 2000; Published in Alföldi, Thomas; Lockeretz, William and Niggli, Urs, Eds. Proceedings 13th International IFOAM Scientific Conference, IFOAM 2000 - The World Grows Organic, page -92. vdf Hochschulverlag AG an der ETH Zürich.

Summary

Knowledge about the amount of fixed nitrogen of different legume crops is very important for calculation of farm N balances. According to literature the choice of determination method may have an impact on the estimated amount of N fixed by a legume sward. The aim of the study was to compare the three most important field methods for determination of nitrogen fixation under different sward management systems. In the present study the natural 15N abundance method gave lower fixation rates than the two alternative methods (total-N-difference method and 15N enrichment technique). The determination of N fixation based only on N in harvestable plant material underestimated the amount of fixed N on average by 70 kg ha-1 compared to techniques including also the amount of N in non harvestable plant parts

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