The variation of ash and inorganic elements concentrations in the biomass of Lithuania- Grown Switchgrass ( Panicum Virgatum L.)

Abstract

Switchgrass (SG) is a perennial grass of C4 type of photosynthesis and has been identified as a potential biomass crop in North America. In Europe, this species has been studied in the Atlantic maritime climate zone and in southern countries. In Lithuania, SG is a novel nonfood crop, whose investigation as a multiuse bioenergy plant, particularly as a feedstock for solid biofuel, has just been started. In this study, our attention was focused on the accumulation of biomass components that have an impact on air pollution and corrosion of combustion equipment, as well as slagging. We quantified the contents of ash and major elements of whole aboveground biomass, stems, leaves, and panicles of SG accessions, promising for growing under Lithuanian conditions. The trials were conducted during 2010-2014 at the Lithuanian Research Centre for Agriculture and Forestry on an Endocalcari- Epihypogleyic Cambisol (CMg-p-w-can). Chemical composition of the biomass was assayed by reference methods. SG biomass, cut at seed maturity had N, ash, K, Cl, Si, and S concentrations averaging 7.94, 56.5, 12.4, 2.79, 4.26, and 0.92 o kg-1 DM respectively. Biomass of SG plants from a collection planted in 2010 had less ash, Mg, and N in both harvesting years than SG from the collection set up in 2011. Biomass of C3 energy plant reed canary grass (RCG) contained higher ash, K, N, S, and Cl concentrations (66.8, 19.1, 14.3, 1.41, and 7.02 g kg-1 DM respectively) compared to those of SG. Genotypic variability in the inorganic composition occurred within SG genotype, but the differences among years were greater than those among accessions. With a delay in harvesting, the greatest reduction occurred in K and Cl concentrations: from September to February K concentration in the biomass of whole aboveground plant part (WP) changed from 12.3 to 3.25 g kg-1 DM and that of Cl altered from 2.26 to 0.590 g kg-1 DM, i.e., decreased by 74 %. Ash, N, and Mg concentration in the biomass declined by 41, 52, and 47 % compared with the biomass cut at seed maturity. Concentrations of ash, Ca, Mg, Si, N, and S in the biomass of stems of all harvesting dates were the lowest compared with the biomass of leaves and panicles. Concentration of K and Cl was practically equal in all plant parts at the respective harvesting time. For all harvesting dates, N and S concentrations in panicles were the highest. Summarising our data presented in the current and previous papers we conclude that SG could be a useful perennial crop with a high potential of dry matter (DM) yield and adequate quality for renewable energy purposes and suitable for cultivation under conditions of nemoral environmental zone of Lithuania. By quality, overwintered biomass is the most appropriate for biofuel production compared to that of harvested in the autumn.