|Abstract in English:|
Title: Poplar stump grinding: analysis of work time and costs.
After harvesting and extracting poplar trees, the agricultural land should be restored for further cultivation by removing the root systems. This operation is done with extraction or stumps grinding using special machines. In Italy, the stumps grinding is actually the operation more practiced. This paper deals with an analysis of work time, productivity and costs of the poplar stumps grinding, performed by two different operators. The poplar plantation was established with Neva (Populus x euramericana) clone and was harvested in march 2012. The plantation was located in Monterotondo (Rome), inside the farm of the Agricultural Engineering Research Unit (CRA-ING). Inside of two experimental plots, of the unit surface area of 0.66 ha, the diameters of all the stumps (220) has been measured in order to establish a correlation between the gross grinding time and the diameter of the grinded stump. The influence of diameter of stump on the grinding cycle time was assessed by a regression of the type T = A + Bx, where T is the gross time of grinding, A and B coefficients to be determined and x is the diameter of the stump. The resulted regressions were subjected to ANOVA test.
The results showed an average work productivity of 111 stumps h-1, with significant differences between operators that underlines the importance of the experience and professionalism of the operator. The productivity obtained on stumps with small diameters (23 cm) can be of 157 stumps h-1 for the expert operator, against about 106 stumps h-1 of a less expert operator. The economic analysis was assessed on a cost per stump and per hectare. In referring to the average of the stumps diameters in the experimental plots (30 cm), a average cost of 1.57 € stump-1 was calculated, corresponding to 522 € ha-1, with a lower cost for expert operator corresponding to 424 € ha-1 (1.27 € stump-1), and a higher cost for the other operator of € 620 ha-1 (1.86 € stump-1).