Work conditions The tillage operations were conducted with several tractor gear conditions. The rotary-type and the crank- type performed with L2, L3, L4 and M1 gear conditions while the plow-type conducted with only L2 and L3 gear conditions. It was due to the fact that operating the plow-type with higher gear speed than L3 was hard. The engine speed was fixed to rated one and PTO speed was also fixed to gear 1 throughout the experiment. The actual rotavating distance was 15 m, and the operati