However, direct contact of stones and clods with potatoes in the harvester causes considerable damage to potato tubers during mechanical harvesting (Yamada, 2007).Consequently, a soil mechanical conditioning (SMC) technique that removes the stones and clods from beds before sowing potato crops has been adopted in Hokkaido. This technique removes the stones and clods from the sowing beds, greatly decreasing the quantity of unwanted material lifted into the machine during harvesting. The result is a reduced