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Incorporation of rice straw in the paddy soil immediately after the rice has been harvested is expected to increase the content of inorganic nitrogen in the soil by the following spring. In practice, however, rice straw is often incorporated during the winter off-season due to labor shortages during the harves. In the present study, the smart system that an unmanned robot-tractor is collaborate-operated for the incorporation of rice straw simultaneously with a combine harvester worked in nearby paddy field plot was examined. The goal of this smart system was the incorporation of rice straw as early as possible while minimizing labor needs. Using this smart system, we showed that the labor needs could be reduced by 13% compared to the local conventional system that rice straw was incorporated by man-operated tractor after rice harvest in autumn or winter. The work efficiency using this smart system was reduced because of unexpected stops made by the robot-tractor due to a malfunctioning obstacle sensor. The yields of rice produced by this smart system was 6-11% higher than that obtained by local conventional system in three rice cultivars. The inorganic nitrogen concentration in the paddy soil applied smart system was a little higher than that with local conventional system. However, there were no significant differences in both rice yield and inorganic nitrogen concentration in soil between 2 systems. These findings demonstrate that incorporation of rice straw using an unmanned robot-tractor on the same day as the rice is harvested could contribute to a reduction in labor and improvement in yield.