Abstract
In this paper we defined the surface F-T which consists of fuel consumption and working time for assessment of field performance in tractor operations.
1) We plotted the various results from field experiments on the surface F-T, and classified these results into the five typical groups.
2) We expected the four typical variations on the surface F-T when the load varied serially in the same tractor operations. Both ΔF and ΔT determined the direction and magnitude of variation, and an operating range of engine speed also effected on the variation types.
3) When we plotted the several results from field experiments on the surface F-T to investigate an effect of load, the two variations of type II and III were observed as the load increased.
4) To promote the rationalization of tractor working systems, we proposed the surface F-T as an index of assessment.
