Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Total soil C and N sequestration in a grassland following 10 years of free air CO2 enrichment
    Kessel, C. van; Boots, B. ; Graaff, M.A. de; Harris, D. ; Blum, H. ; Six, J. - \ 2006
    Global Change Biology 12 (2006)11. - ISSN 1354-1013 - p. 2187 - 2199.
    elevated atmospheric co2 - trifolium-repens l - organic-matter - carbon-dioxide - lolium-perenne - n-15-labeled fertilizer - litter quality - nitrogen pools - forest soils - plant
    Soil C sequestration may mitigate rising levels of atmospheric CO2. However, it has yet to be determined whether net soil C sequestration occurs in N-rich grasslands exposed to long-term elevated CO2. This study examined whether N-fertilized grasslands exposed to elevated CO2 sequestered additional C. For 10 years, Lolium perenne, Trifolium repens, and the mixture of L. perenne/T. repens grasslands were exposed to ambient and elevated CO2 concentrations (35 and 60 Pa pCO(2)). The applied CO2 was depleted in delta C-13 and the grasslands received low (140 kg ha(-1)) and high (560 kg ha(-1)) rates of N-15-labeled fertilizer. Annually collected soil samples from the top 10 cm of the grassland soils allowed us to follow the sequestration of new C in the surface soil layer. For the first time, we were able to collect dual-labeled soil samples to a depth of 75 cm after 10 years of elevated CO2 and determine the total amount of new soil C and N sequestered in the whole soil profile. Elevated CO2, N-fertilization rate, and species had no significant effect on total soil C. On average 9.4 Mg new C ha(-1) was sequestered, which corresponds to 26.5% of the total C. The mean residence time of the C present in the 0-10 cm soil depth was calculated at 4.6 +/- 1.5 and 3.1 +/- 1.1 years for L. perenne and T. repens soil, respectively. After 10 years, total soil N and C in the 0-75 cm soil depth was unaffected by CO2 concentration, N-fertilization rate and plant species. The total amount of N-15-fertilizer sequestered in the 0-75 cm soil depth was also unaffected by CO2 concentration, but significantly more N-15 was sequestered in the L. perenne compared with the T. repens swards: 620 vs. 452 kg ha(-1) at the high rate and 234 vs. 133 kg ha(-1) at the low rate of N fertilization. Intermediate values of N-15 recovery were found in the mixture. The fertilizer derived N amounted to 2.8% of total N for the low rate and increased to 8.6% for the high rate of N application. On average, 13.9% of the applied N-15-fertilizer was recovered in the 0-75 cm soil depth in soil organic matter in the L. perenne sward, whereas 8.8% was recovered under the T. repens swards, indicating that the N-2-fixing T. repens system was less effective in sequestering applied N than the non-N-2-fixing L. perenne system. Prolonged elevated CO2 did not lead to an increase in whole soil profile C and N in these fertilized pastures. The potential use of fertilized and regular cut pastures as a net soil C sink under long-term elevated CO2 appears to be limited and will likely not significantly contribute to the mitigation of anthropogenic C emissions.
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