In order to improve clayey soil in a reclaimed land after draining, the changes of physical properties of the soil and the expansion of crack play an important role. Then, as a fundamental test, we have investigated the behavior of shrinking and slaking of the “ Hedoro” soil-sea bottom clay-to find the change of structural properties of it after receiving repeated action of drying and wetting and also desalinization.
Investigations are made on the three soils: Fresh soil which is extracted from sea bottom having an Electrical Conductivity of 20 mΩ/cm in the 1: 5 soil solution (named K₂₀); Desalined soil of 10 mΩ/cm which is leached from fresh soil with no drying (K₁₀); and the soil leached to 0.4 mΩ/cm in the outdoor lysimeter (K_0.4). Then they are given cyclic drying 0 to 5 times at various stages of soil moisture drying to about pF 3 and pF 4 of soil moisture, air drying and oven drying respectively, before it soaked for the test.
And following results are obtained:
(a) The capacity of holding soil moisture ranging from pF 2 to pF 4 decreases by leaching soil salts.
(b) The structure of soil becomes very compact after desalinization. And the pF value of soil moisture at the point of characteristic transition from Normal shrinkage to Residual shrinkage increases as desalinization progresses:-for the fresh soil it is pF 2.7, for the K₁₀ pF 3.1, and the K_0.4 showes pF 3.5.
(c) When the drying stage of these soils are below about pF 4 of soil moisture, there are little increment of the slaking percentage after receiving alternate action of drying and wetting. On the contrary, when drying exceeds pF 4 of soil moisture, re-wetting results marked slaking.
(d) The K₁₀, which underwent desalinization to some extent but without drying, hardly slakes; while the K_0.4, which received leaching and weathering thoroughly in the outdoor lysimeter, slakes down more easily than the fresh soil.
These results suggest that:(1) In a deep zone, holding a high soil moisture and high salts concentration even after drying, the water pass ability can be maintained during drainage, owing to the fact once produced cracks are hard to close;(2) in a surface zone, physical ripening of soil can be promoted by adequate water management.

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For studying the characteristics of frost and thawy soils, a series of experiments were conducted for the variation of soil strength due to freezing and thawing. Of the factors affecting the strength variations, the moisture properties in particular, were discussed in addition. The findings obtainedare as follows:
1. Freezing and thawing effect reduces the shear strength of soils (Figs. 4, 5 and 9-12).
2. The shear strength is scarcely affected by the time of freezing and thawing duration (Figs. 4 and 5).
3. While the strength of soil decreases gradually to some values with freeze and thaw repetitions, the initial cycle gives the highest reduction rate (Figs. 6 and 7).
4. The reduction of the shear strength due to the freeze and thaw effect depends on the grain size composition involved Finer the grain size, the greater is the reduction rate (Figs. 9-12).
5. Freeze and thaw effect reduces the moisture holding capacity of the soil. The pF values obtained from the shearing test in terms of moisture ratio shows that, the finir the grain size, the greater is its amount of reduction (Figs. 13-16).

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The author made an experimental study of the performance of a moisture meter with strain gauge pressure tranceducer, about the measuring range, response speed, accuracy, etc., and clarified the characteristics of its detection part. The results obtained are summarized as follows:
1) The allowable limit of measurement of negative pressure in this moisture detector is approximately-3, 200g/cm² (≅F3.5). The actual measuring limit somewhat differs according to the kind of soil.
2) The response time of negative pressure measurement in this moisture detector is influenced to a large extent by the size of surface area of a ceramic cup that corresponds to the sensitive part.
3) The response speed of this moisture detector is also varied by the moisture content of soil and the compactness of soil.
4) This moisture detector is capable of measuring the variation of negative pressure potential during infiltration of water inside the -soil layer.
5) This moisture detector constantly shows a stable working condition in the cycle of wetness-dryness of water inside the soil layer ; moreover, the measuring accuracy is high and no temporal change is observed in the detection part.

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Most efficient path in transfering soil with bulldozer is selected by skilled operater. In cutting and banking the soil to make a flat paddy field, a soil transfering programm for most efficient path is desired. The efficiency of soil transfer could be evaluated in terms of:(1) minimum total path length;(2) minimum energy for transfer work; or (3) minimum operation time. One-dimensional model for the determination of minimum path length is illustrated in Fig. 1. Table 1 shows a matrix of soil transfer, in which each figure indicates a distance between starting point and terminal point. In this matrix, if any pair of two rows is exchanged with each other, total of principal values remains unchanged. Therefore, there is no optimum value in a sense of minimum path length.
Problem of energy minimum can be treated as Hich-Kocks type of transportation. Energy of soil transfer Z₁, is supposed to be the sum of products of soil volume x_ij and distance D_ij, that is Z₁=εx_ijD_ij. Minimum of Z₁ is obtained by assuming two conditions:(1) The weight of cutting soil equals to that of banking (coefficient of volume change ε);(2) Each transfered soil is limited to pass once across the borderline between cutting and banking areas. Fig. 4 shows a paddy field which is divided into thirty coordiriate blocks S_i. Let c_i=S_i (h-_h0), b_j=εx_ij, c_i=εx_ij, εc_i=εβb_j, where h₀ is the elevation of rearranged field, c_i is the total volume of soil transfered from the cutting area, b_j is the total volume transfered to the banking area.
The efficiency of earth works V_ij depens on operation distance D_ij of bulldozer as is shown in the previous paper (VIII) V_ij=AQ₀ (1-exp (D_ij/p^h)) f 3600 log (1+D_ij/100)/(1+a) From the inverse of V_ij, and x_ij, the operation time Z₂ is obtained, that is Σx_ij/V_ij. Target function Z₁, Z₂ vary with the combination of feasible solution of {(x_ij)}. Maximum and minimum values of function Z are shown in Table 5. Paths caluculated under the condition are illustrated in Fig. 5, 6. Paths observed at the field are shown in Fig. 7.
The results are summerized as follows:(a) From Fig. 5, 6 and Table 5, the combination of {(x_ij)} in two cases of min Z₁ and min Z₂ are nearly equal to each other;(b) There are some differences between the operation time caluclated by computer and observed time. This is because the soil tranfer with bulldozer is performed by pushing with blade, not by carring, and besides is made by relay operation;(c) In view of time efficiency, the use of two types of machine in combination always fitted is more advantageous for the earth works in paddy field than that of single type like bulldozers. An example of combination may be backetozers suitable for soil tranfer and land graders suitable for levelling paddy field.

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In a previous paper, it was made clear that the optimum conditions of a water distribution pipeline system can be expressed in a very simple form, by introducing a variable φi termed Cost Potential. If we intend to apply this result to practical use, the following are necessary:
1) There is a numerical computation method of. the value of Cost Potential under given conditions.
2) The computing work is practical enough.
3) Some merits are obtainable with this optimization.
In this paper, it is clarified that, first, the values of Cost Potential under given conditions can be determined with a relaxation method. Secondly, its characteristics are investigated from the stand point of practical use by comparing certain computing processes, for example, thore with Dynamic Programing and with Cost Potential. Lastly, the meaning of optimization as discussed here is investigated by giving some application examples.
In consequence, if the problem is restricted to what is set up here, it becomes clear that the method with Cost Potential is superior to that with Dynamic Programing. But the method with Dynamic Programing has wide adaptability to the problems other than that set up here. At any rate, optimization is significant not only in minimization of the total cost but also in the automatic design of pipe diameter.

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Dry farming of paddy field has much been developed under the policy to reduce the rice production, but as the result of charactaristic difference between the farm and paddy fields, several problems became apparent in those farming. Hence we extract and evaluate the matters to be considered in the conversion from paddy to dry farming through the investigation and analysis of their actual situations.
The investigated area is the whole of Kinki region. As the object unit we select the farm group (above 3 ha, of which more than 1/3 is shared by the dry farming area to find the relation with respect to farm land improvement.
Main results is as follows:
i) The area showing good conversion rate in connection with distance from urban districts can be classified crop types in two groups, the substance of which are different from each other. So that it is important to match conversion planning to rocality.
ii) The requirements in land improvement for conversing farm group are:
a) There are farm roads which assure access to each farm by vehicles.
b) Each farm has enough drainability to prevent not only obstacles for crop growth but also the efficiency drop of in-farm working due to furrow wetness.
iii) At present, much problems are concerned to the above a), while for the large scale farms is seem that the b) problems are increasing.

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In the dry farming of converted paddy fields, drainability of field is attached importance for its influence on the crop growth, but the farmers interest is rather facing to in-farm workability, and the relation of drainability to workability at large-scale fields is not clear. However we have founda plenty of data about such a drainage problem at the Dainakanoko reclamation area as follows:
The area consists of large-scale paddy fields improved for rice culture only.
It is easily suffered from overhead flooding because of its lake bottom reclamation in which the drainage depends on pumping only.
Main crop in the dry farming is watermelon which is weak for wettness and requires frequent working in cultivation. Then, making research under these circumstances, the actual state of illdrainage damage was made clear and its mechanism was analyzed.
Main results obtained are as follows:
i) The crop suffers much damage by overhead flooding more than by soil wettness, so that surface drainage enough to avoid the over-ridge flooding is important.
ii) But furrow wettness obstracts the traffic in the furrow to reduce the working efficiency.
iii) The degree of furrow water ponding is different between the longitudinal furrow (parallel to the subsurface drain pipe) and the transverse furrow (perpendicular to the drain pipe). And the differance is largest on the next day of raining when in-farm working such as prevention of disease and insect damage has been done. Therefore it is important to take into consideration of this fact for subsurface drain works in the converted paddy fields.

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