A soil monitor for sugar cane

An under-belt soil monitor based on natural radioactivity has been developed for the on-stream monitoring of the soil content of sugar cane on a moving conveyor belt. The soil monitor consists of a gamma-ray detector and associated electronics, a belt-weigher and a personal computer. The gamma-ray detector is shielded against terrestrial and airborne radioactivity and cosmic rays using lead shielding. The soil content of the sugar cane is computed from the average gamma-ray activity of a rake, the specific gamma-ray activity of the soil and the conveyor load using a calibration equation. Field trials during the 1993 cane harvesting season at the Tully Mill have shown that the monitor can determine the soil content of sugar cane with an FROM deviation of 0.4% soil for soil content in the range 0.6% to 0.6%.