火山性土の凍結並融凍作用が土壌と作物に及ぼす影響とこれが対策に関する研究 (第2報)

抄録

In this report author described the influence of freezing and thawing action of volcanogenous soils on the properties of soil and growth of crops. (1) Influence of freezing and thawing action of volcanogenous soils are differ from the texture of soils. (2) On the volcanic ash soil, excess of water are accumulated from subsoil to surface, so when it melted, excess of water are flowed along to the topography of the earth accompanied with the small particles of the soil, namely soil erosion are occured. Moreover it can be guessed that in spring the drying of the farm are delaid, soil temperature are low, then the sprout of the seed are delaid, accordingly the growth of the young plant are very poor. (3) In the flowed water, it contained soluble nutrients of subsoil which lifted up accompanied with cappilary water, so if the soil erosion are repeated every year, it may be able to guess that surface and subsoils will become sterile by degree. (4) After thawing, soil texture are changed to platy or laminor structure, then the root of crops are developed rather horizontary in the surface soil than penetrats to the subsoil deeply, so the development of the root are poor, yield of the crops are obliged to decreaed. (5) In the frozen soil layer several ice pillar are formed especially near the surface, root of crops and grasses are killed at the point of the ice horizon, nursery trees are pulled up and falled on the surface soil. This phenomena become more obvious when frozen soil are melted. (6) Above mentioned phenomena of volcanic ash soil are true to volcanic sandy soil but it occured merely small scale and volcanic pumice soil are nothing influenced by the freezing and thawing action.