De-inking Sludge Effects on yield and Symbiotic Dinitrogen Fixation Percentage
5th Proceedings International Crop Science Congress, Jeju, Korea
De-inking Sludge Effects on yield and Symbiotic Dinitrogen Fixation Percentage in Forage Legumes in Field by Trace of N-15 (15N)
Iraj Allahdadi1, Chantal J. Beauchamp2, M.R. Labbafi. H.A1, Hamideh Khalaj1
1 Department of Agronomy and Plant Breeding, Aburaihan Campus, University of Tehran; 2 Departement of phytology, Faculty of Agriculture and Food Sciences, University of Laval, Quebec, Canada
The paper de-inking process produces a waste by-product, de-inking sludge (DS), that contains paper fibers, clay particles and inks, and has high C and Ca and low N and P concentrations (C:N ca. 240). In a two-year field study (1995 and 1996), three DS rates (0, 50 or 100 Mg dry matter ha-1) were evaluated on forage legumes established on two soil types in Eastern Quebec, Canada. Symbiotic N2 fixation (SNF) was measured in alfalfa (Medicago sativa L.), sweetclover (Melilotus officinalis L.), red clover (Trifolium pratense L.), birdsfoot trefoil (Lotus corniculatus L.); bromegrass (Bromus inermis L.) was used as the reference (non N2-fixing) crop. Percentages of N derived from the atmosphere (Ndfa) were estimated by: 15N-natural abundance, 15N-enrichment and total N difference methods. The percentages of Ndfa, estimated by the three methods, increased significantly with DS in the first year (1995), but the 15N-enrichment method did not provide reliable estimates of N2 fixation. In 1996,the effect of DS on N2 fixation was observed only at the fist cut, and the trends varied depending on the method used. Our results show that under high rates of application of DS used as an organic amendment, forage legumes grow well following their establishment and derive most of their nitrogen from atmospheric N2. The 15N-natural abundance method appears the most appropriate to estimate dinitrogen fixation during and following the establishment of forage legumes amended with DS.
Key words: de-inking sludge, forage legumes, 15N-natural abundance method, 15N-enrichment method, total nitrogen difference method, reference crop