Claudio Caprara

The use of an electronic beet to evaluate sugar beet damage at various forward speeds of a mechanical harvester

Mechanical harvesting strongly affects the quality of sugar beets, mainly in terms of root injuries, tare, and extracted sugar. In Mediterranean countries, the effects of sugar beet damage are more critical because of the warm and humid climate at harvesting time. In order to investigate the dynamic interaction between mechanical tools and roots, electronic devices have been developed in some European countries for measuring impacts experienced by roots when passing through the harvesters. At the University of Bologna, an electronic beet with a 4905 m/s 2 tri–axial accelerometer was developed in 1998. This device was used in a field trial for measuring and recording impacts in terms of peak acceleration, duration, and velocity change during impact. The device was placed into the soil in place of a real beet and then harvested by a six–row self–propelled harvester, which was tested at four different forward speeds. Assessments of the level of damage on the harvested sugar beets were also carried out according to the IIRB international method. The aim of the study was to evaluate how different forward speeds tested on a single harvester can affect damage to the roots, to assess the damage caused at each step of the harvesting process, and to find a correlation between damage and impacts. Mechanical parameters recorded by the electronic beet were referenced to three specific positions, defined as A, B, and C zones, within the harvester. The ANOVA results in A zone, composed of lifting shares and roller bed, and in B zone, composed of transfer web and turbines, showed a statistical significance. In C zone, composed of tank elevator and tank, the variables had no statistical significance. The results of the trial showed that A zone had the highest values of the variables. A harvester forward speed of 6 km/h caused the fewest taproot breaks and bruises. A linear model describing the relationship between taproot breaks and impact velocity change showed a statistical significance for A zone, while no significance was determined for B zone.

MECHANICAL PROPERTIES OF SUGAR BEET ROOTS

In Italy, as in many Mediterranean countries, different harvesting techniques have been developed for sugar beet. In countries where the multi-stage harvesting of sugar beets is common practice, the roots are deposited on the ground in windrows. The results of previous research demonstrated that the roots, depending on their stay in the field after lifting, are subject to changes in the industrial values of the raw material because of sucrose losses and the formation of non-sugars. It is important to determine how this stay in the field might also change the mechanical properties of the roots, which will later interact with the loader’s mechanical tools on a self-loading trailer. Laboratory tests were therefore done on sugar beets lifted at two harvesting dates. Quasi-static compression and dynamic tests were performed. A preliminary analysis showed that the sugar beet root was composed of homogeneous material for the purposes of determining Poisson’s ratio. In the quasi-compression tests, the value of Poisson’s ratio changed depending on the compression load, while the apparent modulus of elasticity was unaffected. The values of apparent modulus of elasticity were also unaffected by sugar beet harvesting date but changed with the length of time the roots remained in the field after harvesting, showing a higher deformability in roots that had been left just a few hours. In the dynamic tests, the mean values of impact velocity changed and duration increased from roots tested immediately after lifting to roots that remained in the field after harvest.