We investigated the effects of the watering level after sowing on the emergence of spinach (‘Active’: primax seeds) in a plug-transplant nursery system. An emergence rate over 90% was obtained by providing about 200ml of water per plug tray (200 cells per tray, 13ml per cell) regardless of the culture soil component. Contradictorily, a low emergency rate was observed after excessive watering. The emergence rate under a consecutive 25°C condition was 70% or less. The rate was improved by 1) watering with 400-600ml per tray, and 2) subjecting trays to 15-20°C (optimal temperatures for germination) for 3 days after sowing. These management methods promoted about 90% emergence rate even if trays were exposed to a 25°C condition from the fourth day onward. The optimal watering level per plug tray for seed emergence under a condition of 19.1°C were, 100-400ml for normal seeds (with pericarp) and presoaked normal seeds, 200ml for primax seeds, and 400-800ml for naked seeds, respectively. In an optimal watering level, about 90% seeds emerged promptly within 10 days.

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We developed a suitable transplanter (electric semi-automatic type) for a spinach transplanting cultivation system using plug seedlings. This transplanter is light-weight (about 50kg) and optimizes to four rows with 15cm spacing between rows by two operators. Transplant efficiency was equal to or twice that of the hand planting. Labor stress on the bones and muscle system during transplanting using the transplanter showed marked improvement on evaluation by OWAS (Ovako Working Posture Analyzing System). The inclination of the worker's body when transplanting with the transplanter differed depending on the stature of the worker. The influence on the heart rate increase using the transplanter differed depending on worker's physical characteristics.

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To establish a plug seedling transplant cultivation system for spinach using an electric semi-automatic transplanter, the results of cultivation was examined. Stable spinach production in summer was possible, and the growing period of spinach after transplanting in the field (where it was protected by a plastic film greenhouse) compared with that of direct sowing cultivation was shortened up to 70% in late autumn, and 50% in winter. Yield and externals when harvesting were decreased by transplanting plug seedlings shallowly. Decrease in the proper transplant rate because of differences in the harrowing ratio was entirely due to the generation of shallowly transplanted plants. Decrease in the transplant accuracy was able to be prevented by plowing clods to less than 9.5mm in diameter. The pulling out success rate was increased because of an increase in water content of the rootball by subirrigating seedlings before transplanting. The rootball formation rate and the pulling out success rate were increased by double seed sowing.

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A measurement system that measures the power requirement of a work machine was developed to clarify the conditions of applicability of pan breakers and trenchers. These implements are used for the improvement of field drainage in the Jahgaru soil region. This measurement system is composed of a multi-channel data logger, a notebook computer, a clinometer, an ultrasonic distance meter that measures the depth of work, a three-point linkage type traction resistance meter, and a torque meter that measures the power requirement. The traction resistance meter that was prepared for a trail product had an error rate within 5%; the range of the maximum vertical load was 5kN, and the maximum moment 20kN·m in the horizontal load was in the range 0-30kN. The time series of the traction resistance, PTO axis torque, work depth, and inclination (pitching) could be measured simultaneously, which facilitated the understanding of the local change in the state of work and the power requirement since this measurement system was used in measuring the work of trenchers.

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