著者

東 順三 長沢 藤延

出版者

神戸大学農学部

雑誌

神戸大学農学部研究報告 (ISSN:04522370)

巻号頁・発行日

vol.11, no.2, pp.325-330, 1975

---

含有粘土の種類を異にする土壤における粒団生成の実態を明らかにする目的で, 前報のハロイサイト系人工土壤における粒団の造成実験に引続き, 本報ではモンモリロナイト系人工土壤(ベントナイト粘土・海砂・ガラス玉混合物)に腐植, アルミニウム, 鉄および土壤改良剤(アロン・ソイラック)を施用し, 前報と同様に, 湿潤と湿乾交代の二通りの条件下で1・3・6か月間インキュベートして粒団の造成実験を行った。1. モンモリロナイト系人工土壤においては無施用区にも少量の粒団が生じたから, 膨潤性で高い和水性と電荷を持つ粘土では極性の高い水で加湿されると粒子が相互に引き合ってゲル状に集合し, その一部が比較的強固に連結して耐水性になることがわかった。2. アルミニウム単用区は湿潤条件でインキュベートすると高い粒団生成効果を発揮した。しかし湿乾交代条件でインキュベートすると粒径の大きな粒団が形成されなかったから, アルミニウム単独による土粒連結は耐久性の低いことがわかった。3. 腐植単用区ではほとんど粒団生成が認められなかった。しかし腐植とアルミニウムとを併用すると, 両成分が複合して土粒間の連結に関与し, しかもこの粒団は耐久性が高く, 湿乾交代条件下においても注目すべき高い粒団生成効果を発揮した。4. 土壤改良剤のアロンとソイラックの粒団生成効果は中位程度であった。5. 鉄単用区では肉眼的にも特異な泥塊状の集合体を形成し, その粒団化度は中位で, アルミニウムのように高い粒団生成機能を持たないことがわかった。 / Each of humus, aluminum, iron and soil conditioners was added singly or in combination to a montmorillonite-artificial soil consisting of bentonite, sand stone, and glass beads, and these soils were incubated at a constant humidity, or under the alternate humid and dry condition. The amount of aggregate produced in each soil was determined by wet-sieving after one, three and six months, respectively. 1. Some aggregates were formed even in a control soil owing to the character inherent in the clay, montmorillonite, contained. 2. The aggregate formation of this artificial soil was noticiably affected by the condition of incubation in case of single addition of aluminum. Namely, aluminum showed a remarkable effect upon the aggregate formation under the condition maintained at a constant humidity, but the effect was hardly found under the alternate humid and dry condition. It may, therefore, be considered that the aggregates produced through bridging with hydrous aluminum are relatively unstable. 3. Regardless of the condition, the formation of water-stable aggregates was greatly stimulated when humus was applied in combination with aluminum, whereas each of humus and aluminum was without effect when applied singly. From these reslts, it may be noticed that humus and aluminum have a noticeable additive effect, through their interaction, on the process of water-stable aggregates formation. 4. The effect on aggregate formation was intermediary with each of iron, soilluck (polyvinyle alcohol) and aron (sodium polyacrylate), respectively. 5. The formation of peculiar massive aggregate was brought about by the single addition of iron below, but not above, a certain quantity. Such aggregate was not produced when iron was applied in combination with other materials. From these findings, it may be understood that the behavior of iron differs from that of aluminum.