With the purpose of elucidating the influence of the harvested tea leaves weight and the tea plant height with portable type machine, the grasping forces of each finger in various tea leaves weight and tea plant height were measured. The obtained results are as follows.
1) With the increase of the tea leaves weight, the total grasping forces increased at blade side right handle and engine side left handle. The increasing ratio was 1.5 and 1.4 respectively with the increase of tea leaves weight from 0kg to 12kg. There was not particular influence at other two handles.
2) With the increase of the tea plant height, the total grasping force increased around 20% on the blade side and 25% on the engine side with the increase of the tea plant height from 70cm to 100cm.
3) The distribution percentages of each finger were not influenced neither by tea leaves weight nor the tea plant height. The average percentages were on the 2nd finger 15.1%, on the 3rd finger 30.1%, on the 4th finger 35.5% and on the 5th finger 19.3%.
4) In consideration of the original grasping ability, the 2nd finger contributes a little while the 4th finger contributes too much in tea-plucking operation.
5) The supporting force of the additional operator against the tea gathering bag was around one third of the tea leaves weight.
6) For the labour burden reduction of tea-plucking operation, the operators are expected to rotate to reduce the accumulated burden and the plucking machine should be designed to be adjustable for various tea plant height.

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In order to improve the agricultual production efficiency, it is necessary to design the oprimum scheduling of farm work operation under the condition of farm scale, machine power, working period, and working capacity etc.
In recent years, some decision support systems for agricultural optimization planning have been developed. However, the present system cannot deal with uncertain information such as “approximately 10ha”, “about 8 hours” and other fuzzy data.
In this study, to calculate coverage when puddling and rice transplanting working periods are partially overlapped, we have formulated it as fuzzy linear programming problems.
Membership function of fuzzy constraints and fuzzy goal was determined from answers on the questionarie on puddling and rice transplanting. For example, the target coverage is assumed to be approximately more than 2.4ha because the owned rice paddies have 2.4ha. And the limitation of the working hours is assumed to be approximately less than 44 hours in the working period, and so on. By using membership functions which were obtained in the way described above, each working hours and coverage for multi farm operations in the typical 4 cases were to be found as a fuzzy solution and discussed.

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In order to develop a durable steel roll of the drum type leaf-stripping machine for sugar cane, the wearing characteristics of the leaf-stripping steel roll were analyzed. The obtained results are as follows.
1) The wear resisting rate at the dry portion of the carburizing and induction hardening STKM-17A steel roll showed higher value as compared with the wet portion. The wear resisting rate was 97.3% at the dry portion, 96.9% at the wet portion under the elapsed time of 800 hours, respectively.
2) In case of the setting a limit of the durability to 98.0%, the durable time was about 550 hours at the dry portion, and about 450 hours at the wet portion.
3) The height of knurling was 0.26mm at the dry portion and 0.18mm at the wet portion under the elapsed time of 450 hours, respectively.
4) The wear resisting rate of the induction hardening SUJ-3 steel roll was 97.5% at the dry portion and 97.2% at the wet portion under the elapsed time of 800 hours, respectively.
5) The durable time was about 630 hours at the dry portion and about 520 hours at the wet portion. The height of knurling was 0.35mm at the dry portion and 0.29mm at the wet portion under the elapsed time of 450 hours.
6) The wear resisting rate of the carburizing and induction hardening SUJ-3 steel roll was 97.9% at the dry portion, 97.5% at the wet portion under the elapsed time of 800 hours. These rates showed higher value as compared with the induction hardening SUJ-3 steel roll, respectively.
7) The durable time was about 750 hours at the dry portion, about 620 hours at the wet portion. The height of knurling was 0.43mm at the dry portion, 0.37mm at the wet portion under the elapsed time of 450 hours, respectively.
8) The durable time of the carburizing and induction hardening SUJ-3 steel roll was about 1.4 times longer (the increase of the cane treatment of about 170 ton) as compared with the carburizing and induction hardening STKM-17A steel roll. But, these values should be analyzed under practical field tests.
9) The main reason for lower wear resisting rate at the wet portion could be considered that there is effect of the corrosion on the steel roll surface. In order that the results, cane juice should be eliminated from the steel roll surface after the practical operation.

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In this study, changes in the hardness of soil in paddy fields over time and working efficiencies of rice transplanting using the non-tillage transplanting machine were investigated.
The main results obtained were as follows:
1) The hardness of soil after irrigation were gradually softened over time, but the hardness of soil in some fields did not get soft so quickly as others. So, irrigation for the nontillage transplanting field should be done before the tenth day of transplanting time.
2) The efficiency of the non-tillage transplanting machine were much affected by the hardness of soil. The rate of seedling floating and the rate of miss planting of seedlings increased in the harder soil field more than 0.70MPa. The machine showed good run and less slippage rate in the non-tillage field.

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For the purpose of preventing frequent stone accidents in using bush cutter, we have developed a new cutting system equipped with a fixed blade upper the rotary blade, which is designed to catch grass and cut the way a pair of shears do. Experiments were carried out to know the mowing efficiency and the physical stress on the operators in mowing work. The results were compared with conventional bush cutters (8-cutter blade) without a fixed blade. The major results obtained are summarized as follows.
1) In test mowing of oat grass, with a new cutter equipped with the fixed blade, a slightly mowing efficiency was obtained. The lower rate of mowing efficiency can be attributed to the following factors. (1) Diameter of the rotary blade is smaller than that of 8-teeth blade by 4mm. (2) The cutter head including gear case and blades is heavier than that of 8-teeth blade by about 70%, which may affect mowing operation adversely. (3) Engine was set at high speed of 8, 000rpm, which might have caused the cutter blades to catch less grass, resulting in slower movement of the bush cutter.
2) With the new cutting system, higher mowing efficiency was obtained with engine speed 6, 000rpm (peripherals speed of the rotary blade 21m/sec) than with 8, 000rpm (29m/sec). The lower engine speed allowed the cutter to catch more grass and cut grass with better performance. The result was in contrast to the phenomenon with ordinary bush cutters.
3) Relation between a degree of abrasion on the rotary blade and mowing efficiency was investigated. A used blade with abrasion of about R 0.5 allowed the cutter to catch more grass and to yield higher mowing efficiency than with a new blade.
4) Ordinary cutter blade yield higher mowing efficiency in mowing grass with low cutting load. However, the efficiency declined steeply in mowing thick grass in high density and with high moisture. In Contrast, the new cutting system maintained a stabilized mowing efficiency without being affected by the degree of grass density.
5) The effect of using the new cutting system on the extent of operator's physical stress was also studied. Weight of the cutter head is heavier than that of conventional machines by about 70%, which caused slightly heavier pyhsical stress on the operator.
6) In test mowing with machines equipped with cutter heads of the same weight, heart rates with an ordinary blade increased by 144%, and that with the new cutting system by 138%. Lower rate as observed for the latter was believed to have resulted from moment of inertia and self rotating angular velocity which were less than for an ordinary blade by about 1/2 and 1/3 respectively, corresponding to reduction of about 1/6 in gyroscopic couple force generated on the new cutting system blade. Reduced gyroscopic couple made it easier to operate the machine and reduced pysical stress on the operator.
7) Rate of increase in heart rates in operating the cutting system to mow along concrete wall fence was smaller. Rotary blade of the system, smaller in diameter than that of the fixed blade on top, worked to prevent itself to hit concrete wall and to spatter concrete debris. Also, it worked to prevent the machine to get swung back on hitting the wall. All this resulted in reducing the degree of pyhsical and mental stress on the operator.

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Tuberous roots of yacon (Polymnia sonchifolia) contain a large amount of oligofructans. They have a growing interested as a food for health and as a raw material of oligofructans. Then it is necessary to establish yacon culivation technique.
We tested on the effect of the weight of seed tuber on the growth and yield of yacon.
Three experimental plots were made; 10g plot, 30g plot and 50g plot. Three replications were made on each plot.
The results were as follows:
1) Growth of yacon in all stage tended to the best in 50g seed tubers planting and slow in 10g seed tubers planting.
2) The number of stemes per a plant on November 2 were 4.3 in 10g plot, 5.1 in 30g plot and 5.9 in 50g plot, and it was significance in each plot.
3) The top fresh weight was produced 967g/plant in 10g plot, 960g/plant in 30g plot and 1005g/plant in 50g plot, but it was nonsignificance in each plot.
4) The yield of yacon tuberous roots in the weight was produced 1545g/plant in 10g plot, 1706g/plant in 30g plot and 1712g/plant in 50g plot, and the weight in 50g plot was closed to 30g plot, but it was nonsignificane in each plot.
5) From the yield of yacon tuberous roots in each plot, it was suggested that the weight of seed tuber in planting would be desirable to 30-50g.

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Three kinds of organic fertilizer (sawdust manure, rice straw manure, liquid slurry from dairy cow waste) and a chemical fertilizer were used for 6 consecutive years (1986-1991), and their effects on green-cut corn yield and soil properties were investigated. There was a considerable variation in the year to year foliage dry weight of the corn yield, and it was considered appropriate to determine the ratio of fertilizer effectiveness of organic fertilizer in the field in which it had been consistently used to that in which the chemical fertilizer was applied. The dry weight yield of the field in which the respective fertilizer had been used was found to be 80-90% of that in the fields in which the chemical fertilizer had been applied.
After 3 successive years of organic fertilizer application, we added to the organic fertilizer-applied fields ammonium sulfate, fused phosphate and potassium chloride so that the 3 major components in each field were equal to thet of the chemical fertilized field (N:20kg/10a, P₂O₅:18kg/10a, K₂O:20kg/10a). The results were increased foliage yield (dry weight) in the organic and chemical fertilized fields, with the yield reaching the level in the chemical fertilized fields (N:20kg/10a, P₂O₅:18kg/10a, K₂O:20kg/10a) by the fifth year of constant application successively (1990). The application of 11t of slurry proved to be especially effective for consistently high yield. The sixth-year (1991) yield was highest, and vigorous growth was observed in 6-8 weeks after sowing.
Porosity (void ratio) was reduced in all fields tested, whether organic or chemical fertilizers had been used. Harrowing tented to be easier in the organically fertilized fields. In the slurry-applied fields in particular, the proportion of tiny clods was quite high after rotary tilling.

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The sweet potato is very important crop in the South-West warm region of Japan. Land for sweet potato should be plowed 20 to 25cm deep. If it was operated for deep tillage, a potential pollution hazard was increasing. Our objective in this study was to solve this problem and to establish the technique reducing NO₃-N pollution.
We have attempted to decrease water infiltiration by tillage methods.
We proposed some kinds of tillage systems. New methods of tillage systems included hammering the surface of ridge, the combined treatment (compacted soil layer and hammering soil surface) and conventionally cultivated plot. The method of hammering the surface of ridge tended to show suitable soil water storages than other two treatments.
This newly developed tillage system was found to be more effective in controling infiltration in sweet potato production during growing season, especially as rainy season.
It was obvious that NO₃-N in conventional plot had significantly greater concentration near the soil layer (60cm) in comparison with hammering plot. This might suggest that NO₃-N did not move and stayed in treatment plots. It was found that treatment by hammering the surface of ridge was lower infiltration from surface to subsoil than conventional plot. In conclusion, it was found that the new methods of tillage system contributed to reduce Nitrate-Nitrogen leaching.

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