18 research outputs found
Gangrenous Cutaneous Mucormycosis Caused by Rhizopus oryzae: A Case Report and Review of Primary Cutaneous Mucormycosis in China Over Past 20 Years
N2 fixation and performance of 12 legume species in a 6-year grassland biodiversity experiment
Legume defoliation affects rhizosphere decomposers, but not the uptake of organic matter N by a neighbouring grass
Parasitism effects on white clover by root-knot and cyst nematodes and molecular separation of Heterodera daverti from H. trifolii
Nitrogen fixation and transfer in grassclover leys under organic and conventional cropping systems
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 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.
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 potassiumand phosphorus-availability to sustain clover biomass production