부산대학교 도서관

To increase the number of days for which an agricultural machine in sugarcane filed of Jahgaru soil, which is heavy clay soil found in Okinawa, we developed a simple field drainage improvement technique that included subsoil breaking and drainage pit creation. Next, we determined the effects of this technique by setting the limit working conditions for the machines ; these conditions were derived from field experiments. The limit working condition for sugarcane cultivation, excluding harvesting conditions, was soil water content of ≥ 30%. When the total rain value was ≥50mm, the number of days for which a machine could function was 4 days more than that in a conventional setting. On the basis of these results, the area covered by the machine increased by approximately 4 and 5ha in the planter at summer planting and the hiller at spring and root planting respectively. The cost incurred for creating the drainage pit was approximately 37,000Yen. However, if the renewal timing considered as once every 4 years, then the cost averages to approximately 9,000Yen.