EFFECT OF STRAIGHT AND SPIRAL SUGAR-BEET EXTRACTION PATHS AND LIFT ACCELERATION ON SOIL TARE AND RELATIVE SOIL ADHERENCE

The soil tare, i.e. the relative amount of soil adhering to sugar beet after harvest, should be reduced to lower the increasing costs of soi l disposal and to prevent negative effects on the environment. The loo sening up and removal of soil around the beet basically starts upon li fting. Improvement of soil loosening during lifting may be regarded a prerequisite to further increase the effectiveness of cleaning systems on sugar beet harvesters. The soil loosening effects of nine methods of lifting by extraction and one reference treatment were studied by e valuating the net soil tare (on clean beet basis) and the relative soi l adherence at the stage between lifting and cleaning of beets produce d on marine clay loam soils in 1994 and 1995. In the reference treatme nt, the beets were dug out carefully. The extraction treatments used w ere Vertical (no spiral), large pitch spiral and small pitch spiral li fting paths at slow, moderate and quick accelerations. The net soil ta re was lowest for the quick, small pitch spiral motion: respectively 1 4% in 1994 and 6% in 1995 for comparable beet properties and normal so il moisture conditions. The relative soil adherence increased signific antly with decreasing soil tare. This phenomenon was attributed to the original in situ soil adherence: some soil close to the surface of th e beet is reinforced by rootlets or is located in surface niches and a dheres stronger to the beet. As soil loading during extraction was non -compressive for all extraction treatments, it is highly unlikely that the extraction treatments induced the strong soil adherence at low so il tare.