Abstract
AbstractThe 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.
Highlights
Two promising candidate cellulosic biofuel feedstocks are the C4 perennial grasses Panicum virgatum and Miscanthus 9 giganteus Greef et
This study shows that the high initial annual yields of these first replicated trials of M. 9 giganteus in the United States are sustained beyond 5 years, providing over 35 t haÀ1 in each of years 5–7
Analysis of below-ground biomass dynamics suggests that while shoot production is at the expense of rhizome mass in the spring, this is recovered by late summer
Summary
Two promising candidate cellulosic biofuel feedstocks are the C4 perennial grasses Panicum virgatum and Miscanthus 9 giganteus Greef et. Advantages of C4 perennial grasses include their ability to produce large quantities of biomass with minimal agricultural inputs, allowing for an improved carbon footprint compared to annual row crops. Another source of short-term carbon mitigation by perennial crops, such as M. 9 giganteus and P. virgatum is the capture and storage of carbon into below-ground biomass 9 giganteus and P. virgatum, are herbaceous perennials producing an annual crop of shoots from a perennial rhizome system which stores carbohydrate Another source of short-term carbon mitigation by perennial crops, such as M. 9 giganteus and P. virgatum is the capture and storage of carbon into below-ground biomass.
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