application/pdf, 近年,連続的にナガイモ掘取りを行う機種が開発され,利用され始めている.今回,従来から使用されているバックホー方式(K機)と掘取り方式の異なる3機種(A,SおよびT機)の掘取り機について,作業性能を明らかにするとともに,各掘取り機の負担面積や利用経費について検討した.1)収穫作業に携わる作業者数は6-12人と供試機により異なるが,概して能率の高い機種ほど作業者は多い.2 )各供試機の作業能率は, K機が2.2a/hであるのに対して, A機が5.8a/h, S機は3.8a/h, T機が3.7a/hといずれも高能率である.10a当り投下労働量は,それぞれ27.8-32.4,20.8,21.0,21.9人・時である.3 )各供試機の作業精度は,無傷の本数割合がいずれも98%以上と高く,損傷や掘残しの割合は極めて低い.4 )各供試機の負担面積は, A機が4ha,K機は1.5ha,S機とT機が2.5haであり,その時のha当り機械利用経費は,それぞれ556千円, 1,113 -1,173千円,687千円, 699干円となる.各供試機の導入が不利となる下限面積は, K機を他作業に利用するといずれも0.49-0.56haの範囲である.従って, A機は高能率であるが多くの労働力や前後処理に他の作業機を必要とし,大規模農家向きである.また, K機は作業能率が低いが,少人数でも作業が可能なことから小規模農家に適し,S機やT機は中規模農家に適している., Diggers of the backhoe type, the trencher type, and the plow type have been mainly used to harvest Chinese yams until now. Recently, diggers that can continuously dig the tubers have been developed and the farmers are using them. The harvest system, working capacity, operating accuracies, cost and the coverage of the three diggers (A, S, T) that had been developed in recent years were compared with the conventional type (K). 1) Much labor is necessary, when the working capacity of digger is generally high. 2) The working capacities for diggers A, K, S, T are respectively 0.58, 0.22, 0.38, 0.37ha/h and the worker-hour per hectare is 208 for A, 210 for S, 219 for T, and 278-323 worker-hours per hectare for K. 3) There were no tubers damaged by a mechanical cause in any digger though there were tubers damaged by the labor. The ratio of undamaged tubers was more than 98% for each digger. 4) Coverage that can be harvested for yams during the harvest season is 4ha for A, 1.5ha for K, and 2.5ha for S and T. The costs per hectare are 556, 000, 1, 113, 000-1, 173, 000, 687, 000, and 699, 000 yen respectively. The profitable minimum working areas are the range of 0.49-0.56ha for each machine. Digger A is suitable for use by a large scale farmer and K is suitable for use by a small scale farmer because it can be used by a few people. In addition, S and T are suitable for use by a middle scale farmer.