Clarification of the characteristics of soil aeration at upland field is very important for the evaluation of tillage effect. The dry density method is often applied as the index of soil aeration. However, it is very difficult to take soil samples without disturbance at field. For above reason, we made the portable apparatus for evaluation of soil aeration.
The air permeability experiments were conducted in upland field to monitor the changes of soil aeration after tillage by using portable apparatus as explained above. The experimental results show that the changes of dry density, one of the fundamental properties of soil, can be estimated and the effect of tillage can be estimated.
The results presented in this paper are summarised as follows:
(1) The changes of the dry density of soil after tillage can be estimated by using portable air permeability apparatus.
(2) If the dry density of soils is constant, the variations of soil aeration show the changes of soil moisture content and then the changes of soil moisture content can be estimated.
(3) Because of ununiform distribution of the clod size of soils tilled by a tractor, it is difficult to carry out measuring soil aeration by a direct sampling method.
(4) There is a near connection between the value of Q/(HR) and soil texture.
(5) When we obtain the both values of Q/H and soil moisture content using this apparatus at upland field, it will be possible to estimate the dry density of soils presented tillage effect at upland field.
Note Q: the discharge of air., H: aeration pressure. R: (volume fraction of gas)³/(volume fraction of solid)²

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The shape of the rotary blade which influences the rotary tillage resistance consists of the bending tip portion and the straight portion. As these portions have many dimensions and the complicated form, the multiformity of their factors greatly affects the performance of rotary tillage.
In this paper, the form similarity of the rotary blade were analyzed by the cluster method. The relation between the rotary tillage resistance and the form factor of the rotary blade was analyzed by the multiple regression method. The estimation of rotary tillage resistance was carried out to find the minimum parameter of the form factor, precisely. The obtained results were indicated as follows.
1) The number of measured form factors was 15 variables for 19 kinds of rotary blades. The form similarity of the rotary blade could be grouped 2 classes by the group average method and the medium method.
2) With the 4 main components of the form factors such as B₁, B₂, R₂, R₃ 76% of the 15 variables could be explained.
3) The maximum torque of the rotary tillage was estimated using 7 variables, mainly form factors of R₂, D₂, D₃ and the average torque was estimated only 3 variables of R₃, R₄, Q₂.
4) The estimation were showed better agreement with the maximum tillage torque than the average torque.
5) For the development of the selecting method of rotary blades, further study on form factors and dimensions of the blade is expected regarding various soil conditions.

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The present practice of deep tillage, coupled with abundant organic fertilizer application, had so improved the soil that it became a healthy breeding ground for microorganisms such as nematodes. Nematode population in the 25-50cm region had dramatically increased as compared with soils that were tilled using the conventional shallow tillage. Consequently, the effective control of these parasites became even more necessary.
The purpose of this study is to determine a suitable method for controlling nematodes that live in the deep layers of the soil. To this end, a conventional single injection type fumigator and a double injection type deep fumigator were tested on the field. The results are as follows:
1) On the seventh day after nematicide application, DD gas concentration was more than 10ppm at all points up to 50cm depth. This was true for both the single injection and double injection types of fumigation. However, it was noted that DD gas concentration in the 25-50cm layer was higher for the double injection type as compared to the single injection type. This gives a higher potential for the use of the double injection method. Moreover, rapid gas diffusion in the upper half of the soil layer was implied by the low DD gas concentration values. This could have been aided by the 25-30 degrees Centigrade ambient temperature.
2) On the seventh day after nematicide application, percent mortality ranged from 98% to 100% for both the single injection and double injection types of fumigation. However, nematode population gradually increased to the range of 30-88% on the 30th day after fumigation. This could be attributed to the survival of nematode eggs during nematicide application.
3) The double injection type of fumigator is more efficient because although it used less chemicals, it effected the same degree of mortality on the nematodes as compared to the single injection type. Furthermore, injecting the nematicide to soils with high moisture content and covering the field with vinyl sheet for 30 days both helped in maintaining a low nematode population for a longer period.
Further studies should be concentrated on effecting uniform gas distribution, keeping the gas in the soil for longer periods of time, and finding ways how to eliminate the nematode eggs.

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The authors conducted some experiments from 1978 to 1983, to make clear the effect of watering by could water (10°C) upon the growth of cyclamen (Vuur-baak) cultivated under same conditions every year.
The results obtained are summarized as follows.
1. The summer in 1978 was very hot and in 1980 was very cool.
2. In 1978, the soil temperature at 5cm of cyclamen pot dropped remarkably after watering by cold water, The number of days that the difference between before and after watering overed 10°C, was 16 days in July, 27 days in August and 6 days in September, The temperature of city water fluctuated every day according to the air temperature and to the total amount of claudiness in Ikuta.
3. In 1980, the number of days abovementioned was only 3 days in August in Ikuta.
4. The results of hourly observation for 15-16 August 1978 and for 8-9 August 1983 in Ikuta revealed that watering by could water at 12:30 falled markedly the maximum of soil temperature.
5. In Ikuta, the fresh leaves and flower buds of cyclamen were superior at the plot of water in 1978 and no differences observed in 1980.
6. In Fuchu, no significant differences were observed on these characters of cyclamen at both plot every year. The source of water supply at the Experimental Farm is so deep that the temperature of city water is low (about 15°C) in summer. Then it seems that no significant differences of the growth of cyclamen are according to the small difference of water temperature at both plots.

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