A unique depth control system regulated by independent furrow openers was designed and developed for zero tillage systems. The appropriate furrow opener for the control system was investigated on soft, medium, and hard soils. Three furrow openers (hoe, tine and 2-disc) were evaluated based on furrow shape consistency, lateral and vertical seed distribution, soil penetration and disturbance. Results showed that the hoe furrow opener showed no significant difference in furrow shape even in hard soils with great soil penetration, and the variation of the lateral and vertical seed distributions was reasonable. Thus, the hoe furrow opener was selected for the control system.

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In order to analyze the traveling performance of a wheel from the distribution of ground contact stresses, Gaussian functions were applied to the modeling of the respective normal and tangential stresses. The two functions were superposed to fit the distorted shape of the normal stress curve at a high slip ratio. The previous model over-predicted the tangential stress at low slippage and modifications in the proposed model were developed through consideration of relative slip at the contact surface. Unknown coefficients in the model can be expressed by linear and cubic functions of wheel sinkage. Based on the results, the stress model was extended to apply to arbitrary sinkage. The new model fitted very well to measured tangential and normal stresses. Drawbar pull, torque and rolling resistance could also be estimated with high accuracy.

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Incorrect seeding depth causes poor seed germination, low seedling emergence and poor crop yields. To address this, a control system employing a unique method of regulating seeding depth via an independent furrow opener was designed and built. This study evaluates the performance of this system. Actual soybean seeding showed significant differences in seeding depth between the controlled and uncontrolled rows in the zero tillage treatments and conventional tillage treatments where the plow and rotary tiller were used. The control system effectively placed seeds at the correct depth and seedling emergence was positively improved.

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Near-infrared spectroscopy (NIRS) calibration models for determining grain constituent contents at grain elevators were developed using rice and wheat grown in Hokkaido. The coefficient of determination (r²), standard error of prediction (SEP) and ratio of standard error of prediction to standard deviation (RPD) of the validation statistics were r² > 0.99, SEP = 0.19 % and RPD = 25.2 for brown rice moisture content, r² = 0.99, SEP = 0.09 % and RPD = 9.8 for milled rice protein content, r² > 0.99, SEP = 0.34 % and RPD = 23.1 for wheat moisture content and r² = 0.97, SEP = 0.31 % and RPD = 5.4 for wheat protein content. These results indicated that the accuracy of NIRS was sufficiently high for practical use at grain elevators.

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The objectives of this study were to develop an automatic tray-discharging system for rice seedlings that can automatically carry germinated trays from pallets to conveyors whereby they are then conveyed to the nursery field for further acclimatisation. The designed system consists of three main units: the pallet-conveying unit, the tray-relocating unit and tray-destacking unit. A programmable logic controller with a frequency converter, was used to process the sequential events. The experimental results showed that the system worked at a tray discharge rate of 1,671.8 trays per hour, with a 98.1% success rate for the processes. Farmers appraised the system in terms of functionality and stability. In the future, the system throughput will need to be further increased to allow commercialisation.

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To establish a structural environment suited to the operation of a strawberry-harvesting robot, a rolling-type hanging bench and travelling platform were developed. The rolling-type hanging bench, consisting a bench frame, a driving shaft, a DC motor, a pinion-rack and a rolling plate, moved left and right along the beam of the greenhouse and could change the width of the path. The travelling platform, consisting of a main frame and a table, was a gantry structure that enabled a robot to move both in the path direction and sideways. No severe mechanical vibration during stepwise path travel at speed of 182 mm s^–1 was observed, although negative slippage was occurred. It was verified that the travelling platform performs stable travelling.

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