The discrepancy between plot and field yields: harvest and storage losses of switchgrass

Three separate experiments were planned with the aim of assessing storage losses and discrepancies in biomass yield between plot and field, the latter being poorly studied in spite of the relevant management scale. The results show that storability of switchgrass is remarkable, irrespective of harvest time (summer or post-frost harvest) and bale type (rectangular, soft- or hard-core round bales). Bale weight significantly decreased over time, yet it was almost entirely attributed to a decline in moisture content. Microbial processes appeared trivial and this was corroborated by temperature inset and pH trends. In contrast, significant biomass losses were ascertained during the harvest, which accounted from 35% to 45% of potential harvestable biomass. Biomass not picked-up by the baler machine was up to 17%, while the uncut biomass due to the mower swinging averaged 29%, and it was also significantly affected by the field slope. Because of the lower ash content of basal stems, the uncut biomass penalized biofuel quality and quantity, at the same time. Potential harvestable biomass was similar to that achieved with hand-harvested plots thus revealing that the two considered sources of biomass loss (not recovered and uncut biomass) are mostly responsible of the discrepancy between plot and field yields.