8 research outputs found
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
Immunization status in chronic obstructive pulmonary disease: A multicenter study from Turkey
OBJECTIVE: The purpose of this study is to detect the prevalence and the factors associated with influenza and pneumococcal vaccination and outcomes of vaccination during 2013-2014 season in patients with chronic obstructive pulmonary disease (COPD) in Turkey