2151: Methodological aspects of determination of biological N-fixation of different forage legumes [Methodische Aspekte der Bestimmung der biologischen N-Fixierung verschiedener Futterleguminosen]

Loges, Ralf and Taube, Friedhelm (2002) Methodological aspects of determination of biological N-fixation of different forage legumes [Methodische Aspekte der Bestimmung der biologischen N-Fixierung verschiedener Futterleguminosen]. Paper presented at kick-off meeting of COST-852, Solsona, Spain, 22. - 24. Februar 2002; Published in Helgadóttir, A. and Dalmannsdóttir, S., Eds. Proceedings of the kick-off meeting, Solsona, Spain. Quality legume-based forage systems for contrasting environments., page pp. 101-104. Reykjavík: Agricultural Reserach Institute.

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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