Bioethanol is a promising alternative to fossil fuels and a potential countermeasure to global warming. We have been paying attentions to Erianthus, a perennial C₄ grass, as a raw material for cellulosic bioethanol. Erianthus has high biomass production and strong tolerance for environmental stresses. Although they might be partly at least based on their large and deep root systems, studies on root system development of field-grown Erianthus are limited. There might be, moreover, carbon supply into soil through root turnover in perennial plants including their root exudates, which should be a possible countermeasure to global warming. Because there has rarely been, however, quantitative data on both root turnover and root exudates, we examined the root system development of field-grown Erianthus by soil profile and ingrowth core methods in this study. At the result, root system distribution was confirmed to enlarge into deeper soil layers in the second year after planting. Several root indices obtained in this study suggest that larger amount of thicker nodal and lateral roots might be developed to be larger and deeper root systems in the second year. Possible carbon supply into soil through root turnover in Erianthus was, in addition, roughly estimated to be 140 and 270 g/m² in the first and the second years, respectively, based on data obtained in this study.

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