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Seasonal dynamics of above- and below-ground biomass and nitrogen partitioning in Miscanthus × giganteus and Panicum virgatum across three growing seasons

Authors

  • Frank G. Dohleman,

    1. Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
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  • Emily A. Heaton,

    1. Department of Agronomy, Iowa State University, 1403 Agronomy Hall, Ames, IA 50011, USA
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  • Rebecca A. Arundale,

    1. Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
    2. Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, USA
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  • Stephen P. Long

    Corresponding author
    1. Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
    2. Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, USA
    • Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA
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Correspondence: Stephen P. Long, tel. + 217 333 9396, fax + 217 244 3637, e-mail: slong@illinois.edu

Abstract

The first replicated productivity trials of the C4 perennial grass Miscanthus × giganteus in the United States showed this emerging ligno-cellulosic bioenergy feedstock to provide remarkably high annual yields. This covered the 5 years after planting, leaving it uncertain if this high productivity could be maintained in the absence of N fertilization. An expected, but until now unsubstantiated, benefit of both species was investment in roots and perennating rhizomes. This study examines for years 5–7 yields, biomass, C and N in shoots, roots, and rhizomes. The mean peak shoot biomass for M. × giganteus in years 5–7 was 46.5 t ha−1 in October, declining to 38.1 t ha−1 on completion of senescence and at harvest in December, and 20.7 t ha−1 declining to 11.3 t ha−1 for Panicum virgatum. There was no evidence of decline in annual yield with age. Mean rhizome biomass was significantly higher in M. × giganteus at 21.5 t ha−1 compared to 7.2 t ha−1 for P. virgatum, whereas root biomass was similar at 5.6–5.9 t ha−1. M. × giganteus shoots contained 339 kg ha−1 N in August, declining to 193 kg ha−1 in December, compared to 168 and 58 kg ha−1 for P. virgatum. The results suggest substantial remobilization of N to roots and rhizomes, yet still a substantial loss with December harvests. The shoot and rhizome biomass increase of 33.6 t ha−1 during the 2-month period between June and August for M. × giganteus corresponds to a solar energy conversion of 4.4% of solar energy into biomass, one of the highest recorded and confirming the remarkable productivity potential of this plant.

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