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Fate of 15N- and 14C from labelled plant material: Recovery in perennial ryegrass-clover mixtures and in pore water of the sward

Rasmussen, J.; Gjettermann, B.; Eriksen, J.; Jensen, E.S. and Høgh-Jensen, H. (2008) Fate of 15N- and 14C from labelled plant material: Recovery in perennial ryegrass-clover mixtures and in pore water of the sward. Soil Biology & Biochemistry, 40, pp. 3031-3039.

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The below ground C and N dynamics leading to organic and inorganic N leaching from perennial ryegrass-clover mixtures are not well understood. Based on the hypothesis that four different plant materials would degrade differently, a 16 months field experiment was conducted to determine (i) the source strength of labelled plant residues in dissolved inorganic N (DIN) and dissolved organic N (DON) in pore water from the plough layer, and (ii) the plant uptake of organically bound N. Litterbags containing 14C- and 15N-labelled ryegrass or clover roots or leaves were inserted into the sward of a ryegrass-clover mixture in early spring. The fate of the released 14C and 15N was monitored in harvested biomass, roots, soil, and pore water percolating from the plough layer. No evidence of plant uptake of dual-labelled organic compounds from the dual-labelled residues could be observed. N in pore water from the plough layer during autumn and winter had a constant content of dissolved organic N (DON) and an increasing content of dissolved inorganic N (DIN). A positive correlation between aboveground clover biomass harvested in the growth season and total N in pore water indicated that decaying roots from the living clover could be a major source of the 10 kg N ha-1 being lost with pore water during autumn and winter. The presence of 15N in pore water shifted from the DON fraction in autumn to the DIN fraction in late winter, with strong indications that 15N originated from the living ryegrass. However, 15N in pore water originating from plant residues only constituted 1.5% of the total dissolved N from the plough layer.

EPrint Type:Journal paper
Subjects: Soil > Nutrient turnover
Soil > Soil quality > Soil biology
Environmental aspects > Air and water emissions
Research affiliation: Denmark > DARCOF III (2005-2010) > ORGGRASS - Grass-clover in organic dairy farming
Deposited By: Eriksen, Professor Jørgen
ID Code:16290
Deposited On:29 Sep 2009 13:25
Last Modified:12 Apr 2010 07:40
Document Language:English
Refereed:Peer-reviewed and accepted

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