As the factors to effect on soil-overturning in rotary tillage, the various factors such as soil texture, tilling pitch and the shape of rotary blade are anticipated. This report deals with the relation between tilling pitch and the soil-overturning in down-cut rotary tillage. The index of soil-overturning was used as the soil displacement ratio which was estimated by means of electrical conductivity method. This experiments were conducted in different five levels of tilling pitch ranging from 20.8mm to 72.8mm.
The results were as follows.
(1) From the comparison of electrical conductivity Ec between before tillage and after tillage, soil displacement to the backward by rotary tillage was confirmed in the same manner as the previous report.
(2) The coefficient of variance of Ec value between the measuring points in which the soil mixing KCl was put in surface layer before tillage became larger according to the increase of tilling pitch. Therefore, it is assumed that the variation of soil displacement by rotary tillage becomes large as the tilling pitch increases.
(3) It was proved that the ratio of soil displacement from upper layer to lower layer by rotary tillage decreased with the increase of tilling pitch. On the contrary, the ratio of soil remaining in upper layer after tillage showed the tendency to increase when the tilling pitch increases.
(4) The soil displacement ratio of lower and upper layers by the tillage operation showed significant difference among the plots, and it was confirmed that the performance of soil-overturning by rotary tillage deteriorated with the increase of tilling pitch.

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A series of experiments on tractor operation which was a simple model of studies on judgment and decision behavior for problem solving in farm work were done. 3-axial acceleration, location of tractor, angle of steering, and motion of a clutch pedal which were operated by both human experts and nonexperts were investigated. In consideration of uncertainty of desired performances, there was uncertainty, even experts, on controling steering, but there was scarcely uncertainty on treading on the clutch pedal. These studies will contribute to develop expert systems and fuzzy systems for farm work.

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