Long-term productivity of lowland and upland switchgrass cytotypes as affected by cutting frequency.

A considerable number of studies has been conducted on switchgrass (Panicum virgatum L.) as a bioresource for energy over the last few years. Nonetheless, some important issues concerning the agro-technique are still open. This research examines the long-term total dry matter yield (TDM) and ash content of two lowland (L) and two upland (U) switchgrass cytotypes, as affected by one or two-cut system, under southern EU climatic conditions (44 degrees 33' N). Overall, L produced higher TDM than U (on average 14.9 and 11.7 Mg ha(-1), respectively); two-cut system allowed to produce higher biomass yields (especially in U) than single harvest during the two first years, but it also drastically reduced plant vigour and productivity of all cytotypes in the following two years. Moreover, under two-cut system almost total seasonal biomass derived from the early harvest, while the second cut slightly contributed to the total seasonal biomass, nor it appeared to offset the additional harvest costs. Biomass quality was also significantly affected by cutting frequency, with two-cut system leading to a considerably higher ash content of biomass. Therefore, it is perceived that two-cut system is not worthwhile with U and L cytotypes as bioresource for energy production under southern EU conditions.