Nitrogen fixation and transfer in grass-clover leys under organic and conventional cropping systems

Oberson, Astrid, Frossard, Emmanuel, Buehlmann, Cornelia, Mayer, Jochen, Maeder, Paul and Luescher, Andreas (2013) Nitrogen fixation and transfer in grass-clover leys under organic and conventional cropping systems. Plant and Soil, 371 (1-2). pp. 237-255. ISSN 0032-079X

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Abstract

Background and aim

Symbiotic dinitrogen (N2) fixation is the most important external N source in organic systems. Our objective was to compare symbiotic N2 fixation of clover grown in organically and conventionally cropped grass-clover leys, while taking into account nutrient supply gradients.

Methods

We studied leys of a 30-year-old field experiment over 2 years in order to compare organic and conventional systems at two fertilization levels. Using 15N natural abundance methods, we determined the proportion of N derived from the atmosphere (PNdfa), the amount of Ndfa (ANdfa), and the transfer of clover N to grasses for both red clover (Trifolium pratense L.) and white clover (Trifolium repens L.).

Results

In all treatments and both years, PNdfa was high (83 to 91 %), indicating that the N2 fixation process is not constrained, even not in the strongly nutrient deficient non-fertilized control treatment. Annual ANdfa in harvested clover biomass ranged from 6 to 16 g N m−2. At typical fertilizer input levels, lower sward yield in organic than those in conventional treatments had no effect on ANdfa because of organic treatments had greater clover proportions. In two-year-old leys, on average, 51 % of N taken up by grasses was transferred from clover.

Conclusion

Both, organically and conventionally cropped grass-clover leys profited from symbiotic N2 fixation, with high PNdfa, and important transfer of clover N to grasses, provided sufficient potassium- and phosphorus-availability to sustain clover biomass production.

Item Type: Article
Schools and Departments: School of Life Sciences > Evolution, Behaviour and Environment
Research Centres and Groups: Insect Navigation Research Group
Depositing User: Cornelia Buehlmann
Date Deposited: 16 Oct 2017 08:27
Last Modified: 16 Oct 2017 08:27
URI: http://sro.sussex.ac.uk/id/eprint/70524
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