土壌の物理性

地下水の水みちにおける流速測定

奥山武彦, 芝野和夫, 加藤誠

1996 年 75 巻 p. 3-10
発行日: 1996年
公開日: 2021/11/29

DOIhttps://doi.org/10.34467/jssoilphysics.75.0_3

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Groundwater flow system was investigated at a upland field in the central part of Ibaraki Prefecture. Underground temperature survey was conducted to locate the groundwater vein streams and to determine the place for test boring. The depth down to the top of the groundwater vein stream was estimated to be 2.5 m from the ground surface at the boring point. Groundwater flow rate was measured by means of the groundwater surveyor and tracer test. It was also calculated using the hydraulic conductivity determined by in situ permeability test or effective grain size. The flow rate was less than 10 4 cm/s down to the depth of 3 m, greater than 10 4 cm/s at the depth deeper than 3 m. The flow rate at the depth of 3.6 m outside the groundwater vein stream was one-third of that at the same depth inside it. These results show the location and the depth of the groundwater vein stream estimated by means of the underground temperature survey were correct, and groundwater flows at higher flow rate in the groundwater vein stream than another part of the ground.

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赤井谷地高位泥炭地の保全と水移動

笹田勝寛, 河野英一, 加藤誠, 石川重雄

1996 年 75 巻 p. 11-21
発行日: 1996年
公開日: 2021/11/29

DOIhttps://doi.org/10.34467/jssoilphysics.75.0_11

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High-moor peat land has some useful function in environmental conservation involved by factors of its formation. For its conservation, it is desired to clarify water factor which plays an important part in its formation, especially water flow in peat layer. In this study, it was tried to do its flow in case of Akaiyachi high- moor peat land. The principal results are as follows. The groundwater in shallow layer of high-moor peat land flows down through the shallow layer along the gentle slope from the top of dome. Most of the rainfall flows down through the top layer of high moor peat land along the gentle slope. Most of the rainfall loss is due to the evapotranspiration of sphagna. Most of the groundwater is supplied by the cool water which springs directly from mountainous regions under the peat land to flows horizontally through the peat layer. This cool groundwater brings on decomposition control of plant remains which is indispensable for formation of peat land. In the future, for the conservation of Akaiyachi highmoor peatland, it is desired to conserve these water conditions. Also for the conservations of other high-moor peat lands, it will be pointed out to conserve almost the same water conditions as this peat land.

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塩分を含んだ灌漑水が土壌水分保持特性, 土壌乾燥ストレスに与える影響

アハマッド M.M., 安富六郎, 加藤誠

1996 年 75 巻 p. 23-30
発行日: 1996年
公開日: 2021/11/29

DOIhttps://doi.org/10.34467/jssoilphysics.75.0_23

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土壌の水分ポテンシャル特性曲線は土壌の作物に対する有効水分量を知るために看要である。実験はpF値が毛管と浸透圧ポテンシャルの和で表されると考え,塩分水を含ませた砂壌七のpF曲線を描いた。実験作物には水分ストレスを見るためにコマツナを用いた。コマツナ作物に対する上壌乾燥の実験には塩水処理した浸透圧を含む砂質土の標準水分保持曲線を描いた後に,温度25°C,湿度70%の成育栽培用のファイトトロンを利用した。潅漑の都度,上壌塩分量は增大して十壌内水分浸透圧成分の増大を招く。塩分濃度が増大するに従い,浸透圧成分が増大し,蒸発散速度は低下する。潅漑水の塩分濃度が増せばpFも増大するが,これは作物細胞が有する水分ポテンシァルと土壌水分ポテンシアルとの差が少なくなり吸水量も減少するためである。塩水潅漑における潅漑水の浸透圧ポテンシァルは令上壌水負圧増加の大部分を占め,作物のしおれ点にも関係している。実験の結果,次のことが分かった。pFによる土壌の水分管理には土壌•水分•作物系としての新しい見方が必要であり,乾燥地および半乾燥地の塩性土壌の開発には毛符ポテンシァルと浸透ポテンシャルを考慮したpF値の概念の導入が望ましいことを示した。

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粘土の分散性に対する有機物の影響一日置川造成農地の事例一

川田麻子, 伊丹勝彦, 久馬一剛, 小崎隆

1996 年 75 巻 p. 31-38
発行日: 1996年
公開日: 2021/11/29

DOIhttps://doi.org/10.34467/jssoilphysics.75.0_31

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The effect of organic matter and charge characteristics on clay dispersibility of the soils from a newly reclaimed agricultural land, Hikigawa, Wakayama Prefecture, was investigated from the changes with the passage of six years. The adjacent forest soils were examined as a comparison. In 1987 the reduced plant growth in the reclaimed agricultural land was attributed to the unfavorable physical properties of the soil induced by high dispersibility of clay. However, continuous application of a great amount of organic matter to the surface layer of the reclaimed area since 1989, resulted in an increase in total carbon content by ten times in 1993 in comparison with that of 1987, and also favorable plant growth had been obtained. In addition, during those six years, for the surface layer, clay dispersion ratio had decreased from 25% to less than 10% ; other physical properties such as water-stable aggregate content, solid phase ratio and hydraulic conductivity had also been improved. Little clay dispersion after saturated by sodium ion indicated that the binding agent of clay particles was hardly-exchangeable organic matter rather than easily-exchangeable cations. In contrast, for the subsoil which remained in lower level of organic matter, such changes in physical properties as the surface soil were not observed. Charge characteristics of clay particles in the subsoil largely determined the dispersion behavior.

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ボーリングコアを用いた火山性堆積軟岩の吸水率と締固めにおける最適含水比および粒度組成変化との関係

日笠基嘉, 成岡市

1996 年 75 巻 p. 39-46
発行日: 1996年
公開日: 2021/11/29

DOIhttps://doi.org/10.34467/jssoilphysics.75.0_39

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Fundamental properties, especially specific surface of rock, are useful in order to understand their secondary properties. In boring samples, their fine soil particles are usually lost, therelore another fundamental property instead of specific surface is needed for site investigation. In this study, water absorption of rock, grain size distribution and compaction on volcaniclastic sedimentary soft-rock as called “Mizoguchi Tuff Brecca” were tested. The results obtained are as follows : 1. Water absorption of rock collected by boring does not change significantly t han that of test pit sample. 2. Higher value of water absorption of rock is observed in compaction as grain size distribution changes to fine side due to grain crushing. 3. As water absorption value of rock becomes higher, maximum dry density in compaction becomes lower. 4. Water absorption of rock is not only related to optimum water content but also maximum dry density in compaction, that is similar to specific surface.

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粘土鉱物懸濁態を含む電解質水溶液の電気伝導率測定法に関する実験

杉江昌, 橋谷卓成, 岡崎正規

1996 年 75 巻 p. 47-57
発行日: 1996年
公開日: 2021/11/29

DOIhttps://doi.org/10.34467/jssoilphysics.75.0_47

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吸着現象は,土壌の物理化学性の中で最も盃要な性質のひとつである。また,電気伝導率変化はpH変化と違い,溶液中の全イオン種の移動をリアルタイムに測定することができるという特徴がある。しかしながら,電気伝導率の精密測定は,温度条件や測记ブリッジの精度などに留意しなくてはならない。さらに,十壌溶液中に含まれる懸濁態粒子がイオンの移動を妨宵するため,その電気伝導率の精密測定は困難である。そのため,電気伝導率の変化から吸着現象を解析した例はほとんどない。本研究では,懸濁態水溶液の電気伝導中変化を精密に測定するためのセルを試作し,測定法の開発を試みた。また,試作セルの実用性を確かめるため,粘h鉱物に,リン酸塩を吸着させた際の電気伝導率変化の測定を行った。本研究により,以下の結論が得られた。(1)懸濁態をきむ電解質水溶液の電気伝導率の微小変化を測定することができた。(2)電気伝導率およびpHの変化を併せて測定することは,吸着現象のメカニズム解明に有効であることが示唆された。

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精密水頭差発生装置の開発

菊池智士, 古賀潔

1996 年 75 巻 p. 59-62
発行日: 1996年
公開日: 2021/11/29

DOIhttps://doi.org/10.34467/jssoilphysics.75.0_59

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In order to obtain accurate value of coefficient of permeability of soil in laboratory, it is necessary to measure precisely the hydraulic gradient and the flow rate. A new precision hydraulic head difference generator was developed for this purpose. The new generator is divided into two parts. One is a water supply part which is composed of an outer tank and an inner tank floating on the water of outer tank. The other is a drain tank. When the volume of supply water stored in the inner tank is decreased as a result of percolation, the inner tank becomes light and is elevated by a buoyant force. The dimensions of these tanks were determined in such a way that the hydraulic head difference between the supply and the drain water is kept constant during percolation. The hydraulic head difference and the flow rate are measured by a precision differential pressure transducer and a load cell, respectively. These data are recorded by a computer which also control electric valves so as to enable the automatic operation of percolation test. In order to evaluate the performance of this apparatus, the change in hydraulic head difference was observed during percolation test. A similar test with an ordinary Mariotto bottle was also carried out. The results showed that the hydraulic head difference of the new apparatus was kept in a range of 0.02 cm, whereas that of the Mariotto type fluctuated in a range of 0.5 cm. The principle of the new generator can be applied to other kinds of apparatus which require constant hydraulic head difference.

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八郎潟不耕起移植•育苗箱全量施肥稲作一新農法と環境保全に挑戦する農家の熱意一

田渕俊雄, 長谷川周一

1996 年 75 巻 p. 63-65
発行日: 1996年
公開日: 2021/11/29

DOIhttps://doi.org/10.34467/jssoilphysics.75.0_63

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森也寸志

1996 年 75 巻 p. 67-68
発行日: 1996年
公開日: 2021/11/29

DOIhttps://doi.org/10.34467/jssoilphysics.75.0_67

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