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Alisols define a soil group within the World Reference Base for Soil Resources〔WRB ''(Ch2 Key to the reference soil groups )''〕 Properties include having an argic horizon, which has a specific cation exchange capacity; a predominantly alic properties zone between 250mm and 1000 mm from the soil surface; and no diagnostic horizons other than an ochric, umbric, albic, andic, ferric, nitic, plinthic or vertic horizon.〔 Simply put, alisols are poorly drained soils with a dense subsurface clay layer, which causes a relatively high concentration of aluminum ions in the root zone. There exist mixed forms, for example 'gleyic alisol', that are mainly alisol, but also contain components that are found in gleysols. Alisols occur mainly in tropical and humid subtropical climates, though a few are found in unglaciated landscapes as far north as Brittany.〔Chesworth, Ward (editor); ''Encyclopedia of Soil Science''; p. 36. ISBN〕 Compared to Acrisols and Ferralsols, Alisols have much higher-activity clays and are likely to be found on younger terrains or more geologically active regions such as Kyushu and Chugoku. ==Agricultural use== Alisols are acidic (increased by limited drainage) and therefore need liming, contain few nutrients and therefore need fertilizer, and do not have much surface coherence so are easily eroded. Aluminium and manganese toxicity is a very serious problem in Alisols, because at the low pH of these soils such generally insoluble metals become soluble and can poison plants which are not tolerant of them. Encyclopædia Britannica mentions oil palm, cotton, and maize (corn) as crops suitable to be grown on Alisols, though most crops require very intensive fertilisation for long-term success.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「alisols」の詳細全文を読む スポンサード リンク
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