Growth, yield and mineral content of Miscanthus×giganteus grown as a biofuel for 14 successive harvests

Miscanthus× giganteus, a perennial rhizomatous grass commercially used as a biofuel crop was grown in a field experiment on a silty clay loam soil for 14 years. There were 3 rates of fertilizer nitrogen (N), none (control), 60 kgNha−1 yr−1 and 120kgNha−1 yr−1 as cumulative applications. The crop was harvested in winter and dry matter yield measured. N did not influence yield. Yield, which increased for the first 6 years, decreased in years 7 and 8, but then increased again and was highest in the 10th year averaging 17.7 t ha−1 across all treatments. Differences in total production over the14 years were only 5% between the highest and lowest yielding treatments and averaged 178.9 t ha−1 equivalent to 12.8 t ha−1 yr−1. In the first 10 harvests, 92% of dry matter was stem. Although the study showed N fertilizer was not required, it is considered that an application of 7 kgPha−1 yr−1 and 100kgKha−1 yr−1 would avoid soil reserve depletion. Pesticides were not required every year and the crop can