In order to strongly promote the labor-saving and low cost rice production in Japan, magnification of a field plot and establishment of stable direct seeding technique are urgently required.
Recently, the important size of paddy fields in Tohoku regeon is being magnified enlarged from 0.3ha to 0.6 over 2ha.
Efficient cultural practices and field management suitable for large plot, therefore, should be established for competitive rice production in an international market.
The following five techniques are considered to be secure and adequate seeding depth and for sufficient number of standings, hence reasonably rice gemination rate and sufficient numbers of plant standings, etc.
1) Magnificantion of the plot size of puddy field with ±2.5cm of land leveling.
2) Protection of water harrowing and leveling in paddy field.
3) Good germination rate by introduction of big seeds all in one system.
4) Simplification of operation of system for direct seeding broadcaster.
5) Application of original broadcaster for seeding, weeding, spraying operation.

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We have been cultivation tests of Yacon (Polymnia sonchiforia) since 1987, and their results were reported. But it is not yet tested that the influence of ridging on the growth and yield of yacon.
We tested on the influence of the methods of ridging on the growth and yield of yacon in Light-colored Andosol.
Three experimental plots were made; level row plot, level row→high ridge (by earthing up) plot and high ridge plot. Three replications were made on each plot.
The results were as follows:
1) Growth of yacon of main stem in all stage was nonsignificant difference in each plot.
2) The top was produced 748g/plant in level row plot, 900g/plant in level row→high ridge plot and 904g/plant in high ridge plot, but nonsignificant difference in each plot.
3) The tuberous roots was produced 1268g/plant in level row plot, 1280g/plant in level row→high ridge plot and 1584g/plant in high ridge plot, but nonsignificant difference in each plot.
4) From yield of yacon tuberous roots in each plot, it was suggestted that the earthing up at August 4, it would have little influence on yacon yield.
5) From yield of yacon tuberous roots in each plot, it was judged that high ridge culture would be useful for the harvest of the tuberous roots of yacon with a potato digger.

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The increase of field lot in size enables us to use the machinery more effectively. This effective use of the machinery leads to “SCALE MERIT”. To make the “SCALE MERIT” clear, we have investigated various kinds of field works on fields different in size, and analized the degree of effective use of the machinery which is connected with the increase of field scale. The analysis is made by calculating effective field capacity and effective field efficiency. In the analysis, we divide the total operating time of different field works into actual operating time, turning time (including moving time), loading time of seedling, seed, fertilizer, and unloading time of unhulled rice.
The results are as follows:
1) Actual operating time is influenced by operating conditions (operating speed and operating width). Actual operating time per 10 are changed very much where operating conditions were different. When these conditions were equal, actual operating time per 10 are was almost constant regardless of size.
2) Turning time is influenced by the number of turning times. When turning times of reciprocating work and head land work were equal at any size fields respectively, turning time per 10 are was shorter as the field size became larger. But this was not true or just the opposite when we used the machinery inferior in operating conditions at large scale fields.
3) Loading and unloading time per 10 are was not dependent on the field size when machine capacity and the number of supplementary members were the same.
4) In the investigations into many field works, the operating conditions were sometimes different from field to field. In this case, we could not confirm by effective field capacity the realities of effective use of machinery brought by the increase of field scale. But when the operating conditions were equal, effective field capacity increased with the increase of field lot in size, and therefore the “SCALE MERIT” has been recognized.
5) Even when “SCALE MERIT” was not admitted by analyzing effective field capacity, we could admit it by analyzing effective field efficiency, because effective field efficiency rose with the increase of field lot in size. So, it is found out that effective field efficiency is used as an effective method to confirm the effect of the increase of field size.

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In order to grasp the effect which the operating speed, operating width and the coefficient of field lot form (long side/short side of field lot) exerts on the effective field efficiency, the effective field capacity is calculated by a simulation model. And the relation between field lot scale and the effective field efficiency is analyzed when different farm machinery and farm work machinery are used.
The results are as follows:
1) As the field lot scale increases the effective field efficiency increased at the rice cropping work (tilling-harrowing, puddling, rice transplanting and harvesting) and at the soybean cropping work (tilling-harrowing, planting, intertilling-weeding and harvesting). But the work accompanied by loading (seedling, fertilizer and seed) and unloading (unhulld rice) did not show much increase in the effective field efficiency. That shows there is little usefulness brought by increase of field lot in size. And the effective field efficiency of harvesting of soybean cropping showed a tendency similar to that of the tillingharrowing and others because the unloading time was excluded.
2) The effective field efficiency decreased with the increase in operating speed. The discrepancy of effective field efficiency caused by the difference in operating speed was ramarkable in the work related to the loading and unloading.
3) The effective field efficiency decreased with the increase in operating width. The discrepancy of effective field efficiency caused by the difference in operating width was remarkable in the work related to the loading and unloading. But if t₁ (turning time of reciprocating work) is much larger than t₂ (turning time of head land work), the effective field efficiency in the wide operating width is higher than that in the narrow one.
4) The effective field efficiency in creased with the increase in the coefficient of field lot form. And such phenomena were remarkably found on smaller field lot scale.

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Rice cultivation by the transplanting of infant seedlings was investigated in Ibaraki Prefecture. The results were as follows:
1) All the farmers used rockwool mats, while they have had different practices such as sowing rate, quantity of irrigation water, nursery period and so on. Days from sowing to the transplanting of seedlings varied from 10 to 20, and leaf age at transplanting from 2.4 to 3.2. Plant length of seedlings at transplanting was more than 8.0cm.
2) The average number of planted seedlings per hill was from 6.1 to 8.4. This figure was higher and variable than the usual one, 4 to 5. Higher percentage of vacant hill was brought about by higher fluctuation of the number of planted seedlings per hill.
3) The time needed for the rearing of infant seedlings was reduced to 49% of that for the rearing of young seedlings. But replanting time for infant seedling cultivation required 72% more than that of young seedling cultivation, because of high rate of vacans hill in infant seedling cultivation.
4) Rice yield in the infant seedling cultivation was nearly the same as that of young seedling cultivation. It is expected that low cultivation cost in infant seedling cultivation will be achieved by means of the improvement of transplanting accuracy.

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The mixing of barley grain with volunteer wheat grain causes a serious problem in wheatsoybean-barley rotation. This report describes the relationship between the persistence of volunteer wheat and the mechanical weeding method in soybean culture. Control of volunteer wheat by inter-cultivation and ridging in soybean fields was effective. During the summer, most volunteer wheat plants died from drying or burying.
Inter-cultivation and ridging had killed wheat grain and wheat seedlings at a soil layer of 0-6cm deep. So when inter-cultivation and ridging were used in the cultivation of soybean, volunteer wheat decreased in fields where barley were planted by no tillage. But when inter-cultivation and ridging were also used in the cultivation of soybean, volunteer wheat increased in fields where barley were planted by rotary tillage. The reason why volunteer wheat increased in this field was that the wheat grain at a soil layer of 7-15cm deep was moved to suitable depth of emergence by rotary tillage.
In wheat-soybean-barley rotation, the best means were to prevent the mixing of barley grain with volunteer wheat grain by the combination of inter-cultivation with ridging in the cultivation of soybean, and by no tillage in the cultivation of barley.

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This study was conducted to improve some pratical techniques for reducing both production costs and labor hours in crop rotation system based on the rice culture seeded on the dry field.
Soil packing after tillage was thought to be an important technique for the rice culture seeded on the dry field in Hokuriku district where has much rainfall in spring and winter. The experiment on rotation system consisting of 5 crops, (rice culture seeded on the dry field, rice culture seeded on the dry field, barley and soybean, and rice culture seeded on the dry field) was carried out in the 1.8 ha field for 4 years.
1) The soil after the rice culture seeded on the dry field showed high porosity, low plasticity index and no spreaded sign of grey horizon. This phenomenon meant to be the good conditinos for rotation crops such as barley and soybean. In the 4 year crop rotation based on the rice culture seeded on the dry field, the grey horizon decreased and the iron mottles increased in the soil structure.
2) The number of turns per unit area of large-lot field (210m×85m) were less than that of small one. So, the effective field capacity (ha/h) increased and the working efficiency was improved.
3) The total labor hours required for the rice culture seeded on the dry field was 13-14h/10 a, because of efficient work and management in the large-lot. This was about 1/3 as long as the hours required for the conventional transplanted rice culture.
4) The total labor hours required for the barley culture in the chop rotation system was 3.6h/10a (except drying and processing), and that for soybean culture was 6.9h/10a (except drying). These labor hours were about 1/3-1/2 as long as those for conventional culture.
5) In the rice culture seeded on the dry field, slow-release type fertilizer was incorporated as a basal dressing and irrigation water were supplied at 1.5-2.5 leaf-stage of rice seedling when was earlier than the usual. Therefore, rice plants showed higher rate of establishment (55-80%) and vigorous growth in later stage. The yields of Koshihikari and Kinuhikari were 512-577 and 523-630kg/10a, respectively. These yields were almost the same level as transplanted rice culture.
6) The well-drained field conditions made it possible to cultivate barley and soybean by the drill-seeded culture without additional drainage trenches. So, the yields of barley (Minorimugi) and soybean (Enrei) were 635 and 346kg/10a, respectively. These yields were about 2-3 times as much as those of conventional culture.

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