Mobilization of minerals and moisture loss during senescence of the energy crops Miscanthus×giganteus,Arundo donax and Phalaris arundinacea in Wales,UK

Miscanthus×giganteus, Arundo donax and Phalaris arundinacea were planted at three sites in Wales, UK, to study the timing of mineral and moisture decline during autumn and winter. The mineral and moisture content at several harvest dates throughout the period were compared with power station threshold levels. All crops showed a highly significant decrease in moisture content in all years with the exception of Arundo which did not lose moisture in the final year. The Miscanthus and Arundo crops remained above the moisture content threshold in all years and would require further drying before combustion. The Phalaris fell below the moisture threshold in January. The Miscanthus leaves fell below the nitrogen threshold before leaf abscission at one site but not at another, although the cane remained mostly within the guideline range. Both its leaves and cane remained above the potassium threshold level. Its leaf sulphur fell within acceptable levels during November and its cane remained below the lowest threshold from November onwards. The Arundo leaves remained above the nitrogen, potassium and sulphur thresholds throughout the period and it did not lose its leaves. The cane nitrogen increased above the threshold during autumn whereas its potassium remained higher than its threshold, with the exception of one sampling date at one site. Its sulphur remained within the guidelines. The Phalaris crop fell to within nitrogen guidelines at one site but increased at the other. Its potassium decreased to below the threshold at both sites in January, and its sulphur content was consistently within the guidelines.