Soil dynamics of the origination of soil tare during sugar beet lifting

High soil tare of sugar beet on wet clay soil after uprooting with share lifters is usually attributed to the fact that the soil becomes sticky due to mechanical impact during uprooting. Results of field experiments have shown good potential for obtaining low soil tare of sugar beet on wet clay soil by beet extraction with a high average vertical acceleration and a spiral extraction path with a small pitch. The objective of this research was to provide models for soil-beet-lifter systems used in these experiments, and to simulate some of the observed effects of the uprooting method on soil tare and soil adherence. As the rootlet system plays an important role in the origination of soil tare, the rootlet system was also modelled. A constitutive soil model, assuming elastic-perfectly-plastic soil behaviour, was used as a basis for modelling soil-beet-lifter system variants, including beet with and without rootlets, uprooting by extraction, rotation and extrusion, and uprooting with low and high vertical acceleration. The origination of soil tare is presented on the basis of the calculated zone of initial soil failure during extraction. Expected soil adherence is discussed in relation to the stress state of the soil. The simulated initial soil failure and stress state of the soil agreed well with experimental results on soil tare and soil adherence. (C) 2002 Elsevier Science B.V. All rights reserved.