Manipulating the N release from N labelled celery residues by using straw and vinasses |
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| Authors: | B Chaves S De Neve C Berko G Hofman |
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| Institution: | a Department of Soil Management and Soil Care, Ghent University, Coupure Links 653, 9000 Gent, Belgium
b Laboratory of Applied Physical Chemistry (ISOFYS), Ghent University, Coupure Links 653, 9000 Gent, Belgium |
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| Abstract: | The aim of this laboratory study was to investigate the effect of straw and vinasses on the nitrogen (N) mineralization-immobilization turnover of celery residues during two periods (each simulating a time period from autumn till spring) under laboratory conditions. During the first period (1-198 d), 15N-labelled celery residues (1.1 g dry matter (DM) kg−1 soil) were incubated together with straw (8.1 g DM kg−1 soil), aiming to immobilize the N released from celery residues, followed by an incorporation of vinasses (1.9 g DM kg−1 soil) after 84 d, with a view to remineralizing the immobilized celery-N. During the second period (198-380 d), the experimental set-up was repeated, except that non-labelled celery residues were used. Total N, mineral N and their 15N enrichments as well as microbial biomass N were determined at regular time intervals. During both periods, mixing celery residues with straw significantly increased microbial biomass N (90.5 and 40.5 mg N kg−1 extra compared to celery only treatment) and decreased the amount of mineral N (reduction of 56.1 and 45.9 mg N kg−1 soil compared to celery only treatment) and the celery-derived mineral 15N (0% of mineral celery-derived 15N in straw treatment compared to 35% of mineral celery-derived 15N in celery only treatment). After maximum immobilization, a natural remineralization (without addition of vinasses) of 32.2 (at day 198) and 11.1 mg N kg−1 soil (at day 380) occurred in the straw treatment, but the mineral N content remained significantly lower than in the celery only treatment during the complete experiment, and the amount of remineralized celery-15N was very low (5.4% of celery-derived 15N after 380 d). Vinasses caused no real priming effect, although it did slightly increase the amount of remineralized celery-15N (+6.4% of celery-derived 15N at day 380 compared to the straw treatment), probably due an apparent added N interaction caused by displacement reactions with the soil microbial biomass. |
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| Keywords: | 15N-labelled celery residues Straw Vinasses Organic wastes N immobilization N remineralization |
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