Planting of Allium × wakegi Araki bulbs is physically strenuous because it is performed manually with a squatting position. Therefore, we have developed a simplified planting machine that can be used for planting Allium × wakegi Araki bulbs and a planting method. This study aimed to elucidate the effects of using this planting machine for the cultivation on subjective exercise intensity, work time, work position of laborers, and the subsequent plant growth. In order to improve the working posture during the use of the developed system, the working posture was evaluated using the OWAS method; the results demonstrated that in 90% of the control group, postures need consideration in the near future (AC3), while more than 90% of the treatment group showed normal postures which do not need any special attention, except in some special cases (AC1) and postures must be considered during the next regular check of working methods (AC2). Furthermore, the subjective exercise intensity at the end of the work during subjective evaluation was based on the modified Borg Scale; complaints of the lower back was 5.7-7.7, thigh was 3.3-8.8, and knee was 1.3-5.7 in the control group, complaints of the thigh was 0.7, knee was 0.3, and calf was 1.0 in the treatment group. The work time during planting was reduced significantly; however, a decrease in the entire working duration, including the preparation, was not observed. A countermeasure was considered that might improve the efficiency of loading the bulbs into the connected paper pot that occupies 59-83% of the total. The sprouting and rooting days and the growth and yield obtained using the planting machine were comparable to the bulbs that were manually planted.

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Experiments assessing direct-seeding rice cultivation using plowing and compaction were conducted in large Muck soil paddy fields (soil texture of plow lyre: lite clay) of 3 ha scale to establish a method of reducing paddy field water requirements of rice-cultivation methods using compaction. A laboratory compaction experiment based on the soil hardness index clarified the soil hardness necessary to reduce the water requirement. Results show that saturated hydraulic conductivity decreased to 2.3×10^-5 cm s^-1 by compacting soil to 20 mm of soil hardness with more than 34% soil water content. After four repetitions of whole field surface compaction using a Cambridge-roller in the field experiment, the soil hardness at 5 cm under the field surface increased to about 20 mm, as measured using a soil hardness meter. Results show that saturated hydraulic conductivity at 5 cm under the field surface decreased to the targeted level of 2.3×10^-5 cm s^-1. The water requirement in experiment fields compacted with the Cambridge-roller decreased to about 10 mm d^-1, which is lower than our targeted value of 20 mm d^-1. Investigation of the water level at the paddy surface and in the subsurface drain pipe revealed that the paddy surface water level in compacted paddy field was maintained by the compacted soil layer at 5 cm depth under the field surface because of a discontinuity of water levels between the paddy surface and the subsurface drain pipe. Results show that field surface compaction with index value of soil hardness reduces the water requirements of a large paddy field.

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Rice cultivation using potted-seedlings is practiced mainly in cold regions. The technique limits plant injury during to transplanting and promotes tillering ability, which may in turn reduce damage to rice plant roots by the rice water weevil (RWW) early in the growing season. We assessed the effect of RWW infestation on the growth and yield of rice by releasing RWW adults on rice plants cultivated from potted and conventionally grown seedlings in the field and in pots. In the field experiments, the tiller number of rice plants exposed to RWW tended to be lower than in control rice plants grown from potted and conventional seedlings during the early growing season (40 to 50 days after transplantation (DAT) ). In addition, the tiller number of rice plants cultivated from potted seedlings tended to be higher than the tiller number of plants cultivated from conventional seedlings. In the pot experiments, above-ground dry biomass, root dry biomass, and exudation rate tended to decrease after RWW infestation in rice plants cultivated from potted and conventional seedlings. However, these parameters tended to be higher in rice plants cultivated from potted seedlings than from plants cultivated from conventional seedlings. The findings suggested that using potted seedlings reduces the potential for damage by RWW during the early growing season. However, since the tiller number of many of the rice plants damaged by RWW had recovered by the heading stage in the field, the benefits of using potted-seedlings to minimize RWW damage early in the growing season is not reflected in improved rice yield.

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