Oberson, A.; Frossard, E.; Bühlmann, C.; Mayer, J.; Mäder, P. and Lüscher, A. (2013) Nitrogen fixation and transfer in grassclover leys under organic and conventional cropping systems. Plant and Soil, (online), - .
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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.
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.).
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 gN 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.
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 potassiumand phosphorus-availability to sustain clover biomass production.
|EPrint Type:||Journal paper|
|Keywords:||15N natural abundance, Grass-clover ley, N transfer, Organic cropping, Symbiotic N2 fixation, Trifolium spp., Bodenwissenschaften, Stickstoff, Systemvergleich, Langzeitversuch, DOK|
|Subjects:|| Soil > Nutrient turnover|
|Research affiliation:|| Switzerland > FiBL - Research Institute of Organic Agriculture Switzerland > Soil Sciences|
Switzerland > Agroscope > ART - Reckenholz location
Switzerland > ETHZ - Agrarwissenschaften
|Deposited By:||Mäder, Paul|
|Deposited On:||05 Sep 2013 12:55|
|Last Modified:||05 Sep 2013 12:55|
|Refereed:||Peer-reviewed and accepted|
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