Abstract
The study aimed to evaluate the aboveground dry biomass production and the quality of fresh and dried chips obtained by eight different species grown under SRC culture and subjected to two harvesting systems and chipping devices.
The present study was part of a long project including different species and management regime of a SRC plantation, which was established in 2007 on a level soil at the Improsta experimental farm (Eboli, Salerno, Italy).
In 2015, It was realized a comparative test chipping eight different species grown under SRC system: Fraxinus oxyphylla, Robinia pseudoacacia, Salix alba, Populus nigra (Limatola) and four hybrid genotypes of Populus x euroamericana (Grimminge, Vesten, Hoogvorst, Muur), harvested at the end of the first three years rotation coppice (2012-2014).
The trees were chipped both fresh and dried. The fresh biomass was harvested and chipped in a single phase by a self-propelled forage harvester Claas Jaguar 880 (nominal power of 353 kW), equipped with GBE biomass head for trees cutting and harvester feeding. The dried biomass was chipped by a forestry wood disk chipper Farmi Forest CH 260, after two months of storage in the field.
The plantation mean of the standing aboveground dry biomass was greater for P. nigra Limatola, followed by F. oxyphylla. As consequences, they showed respectively a high mean annual increment of aboveground dry biomass of 14.38 and 10.16 t ha-1 year-1. The first coppice rotation dry biomass yield was not significantly different for Hoogvorst and Vesten. In contrast to the biometric attributes clone Muur showed a low aboveground dry biomass production, followed by Grimminge and S. alba with a significantly lower production. Moisture content of the fresh biomass ranged between 42.59 % and 56.84 % for black locust and willow, respectively. The dried biomass ranged, instead, between 17.32 % for willow and 36.80 % for Populus nigra. The average reduction of moisture content after storage was 43.97 % with the highest and lowest rate of dehydration for willow (69.53 %) and poplar Vesten (28.70 %).
Concerning the particle size distribution, the presence of large chips (63-45 mm) and oversized (> 63 mm) were extremely limited for the fresh chips, while it is considerably higher for the dried chips. Fractions ranging from 45 to 3 mm were the most represented for all species and treatment, accounting between 84.09 % and 90.65 % for the fresh chips, and 74.15 % and 85.68 % for the dried chips. The comminution carried out with the disk chipper on dried biomass always leads to a decrease in the percentage of accept (45-3 mm fractions) respect to the same fresh species chipped by drum chipper.
