To retain summer runoff rain-water, an artificial perched watertable was constructed at about 0.5 m depth in an area where the annual precipitation occurs mostly in the summer season. The water in the sand-filled permeable layer could be used as capillary water for plants in the dry spring season. A special machine was developed to create the artificial perched watertable. This paper deals with the field operation testing of this machine.
The results showed that when the soil water content was more than the plastic limit (PL) and the soil penetration resistance of the field was less than 2 MPa, the penetrating velocity of the injector into ground was constant at about 50 mm s⁻¹ and a insert of 0.5 m in depth was obtained. A perfect underground cavity was produced due to the horizontal rupture fracture of the soil, when the soil water content was more than 25% d.b. Hence, when this machine is operated in a field, in order to obtain the perfect insert of the injector and the perfect underground cavity production, the soil water content should be more than the plastic limit. Charging air into the charge tank and charging sand into the sand tank occupied 98% of the total time. Charging air into the charge tank required 93% of the total operating energy.

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An artificial perched watertable was constructed by a watertable construction machine at about 0.5 m depth from the soil surface in an area where the annual precipitation occurs only in the summer season to retain summer runoff in this watertable. The zone of capillary diffusion from the underground watertable during dry season for seven months from September to March in which no rain occurs was determined in an indoor soil bin which had a transparent side and a float and needle system to maintain water at a constant level. The results showed that water proceeded quickly into a whole sand layer and then into a clay soil layer. When the capillarity diffused into three-dimensional clay soil layer, the maximum length of the capillarity was 4.1 m in horizontal direction and the minimum length was 0.95 m in vertical direction for the seven months. Hence, the distance required to operate the watertable construction machine was 11.2 m.

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To elucidate the phenomenon of the soil compaction observed during actual machine operation, a model wheel was traveled repeatedly and the subsequent soil deformation was analyzed. As repetitive travel progressed, soil particles drew similar trajectories with accompanying changes in the size and shape of the trajectories leading to the formation of spiral-like patterns. The changes depended on traveling slip and depth of the soil layer. The void ratio increased in with repetitions in the shallow layers, but decreased in the deeper layers. The change in void ratio in high slip conditions was larger than those in low slip conditions, indicating that repetitions in high slip caused more deformation and compaction than did those in low slip.

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To ensure food safety of leafy vegetables such as lettuce, Perilla, and flat Chinese cabbage, various microorganisms and foreign materials commonly found on the leaf surfaces must be removed or inactivated by sterilization before these the food is consumed, especially when served in large restaurants or school cafeterias. This study was conducted to develop a washing and sterilization system for leafy vegetables. Results showed that the optimum washing times using air bubbles for lettuce and Perilla was five minutes and for flat Chinese cabbage was ten minutes. The percentage of bacteria removed after the optimum washing times were 94, 98, and 76% for lettuce, Perilla, and flat Chinese, respectively. The system was developed so that leafy vegetables contained in a box were continuously moved to pass through the washing, sterilization, and dehydration stages.

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A method is proposed for soil improvement of salt-affected soils. We envisaged that a layer of about 600 mm in depth could be tilled by a special plough, producing a coarse layer (soil clods) in the subsoil (B and C horizons) and cutting off the capillarity rise of groundwater. In this paper, indoor testing with soil bins was used to determine the proper size of the soil clods produced in the subsoil which will be used for design of a new plough configuration.
The results showed that the porosity of the subsoil reached 0.49 where capillarity restarted, after 2000 mm of precipitation. The size of the soil clods of the B horizon should be about 10 cm to prevent collapse and loss of volume of the topsoil (A horizon). That of the C horizon should be about 14 cm to keep a longer capillarity interception.

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This paper presents an autonomous guidance system of a wheeled tractor-like-robot on sloping terrain. A Neural Network (NN) vehicle model was developed for sloping land and trained using Back Propagation algorithm. Genetic algorithms were used to search the optimal steering values for different combinations of lateral and heading deviations. Using those values, a NN-based steering controller model was designed to generalize the optimal steering for different land-inclinations. Autonomous travel tests were conducted with a prototype test tractor along predetermined rectangular paths on sloping lands. It was found that the tractor could precisely follow the paths. The mean and standard deviation of the offsets along four linear directions of the rectangular path on 15° sloping land were 0.058 m and 0.063 m respectively, which are insignificant for tractor motion on agricultural farms.

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