Distribution and Acid Injury of Non-allophanic Andisols.

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Non-allophanic Andisol admitted as one of the subgroup in International Andisol classification ( ICOMAND ), has strong soil acidity and is thought to be a problem soil. Therefore, both distribution and acid injury of non-allophanic Andisol were examined in this study.1) Andisol was divided into allphanic and non-allophanic Andisols by the constituent of amorphous material and was studied their chemical, physical and mineralogical properties. Both Andisols showed some common unique properties such as high amount of active Al, high accumulation of humus, low bulk density etc. Non-allopghnic Andisol showed, however, very strong soil acidity, while allphanic Andisol showed weak one.2) The acid injury of non-allophanic Andisol was clarified to be Al3+ toxicity and the degree of Al3+ saturation, the amount of exchange Al3+ and exchange acidity y1 were more useful measure of A1 toxicity in the acid Andisols compared to the amount of soil solution Al3+. Among these measurement, the y1 is most simple and practical method and 6 of y1 is worth to 2me of KCl-Al3+ which is diagnostic value differentiating alic subgroup of ICOMAND.3) Both barley and sorghum grown in non-allophanic Andisol showed symptoms of Al-toxicity and the growth of these plants was much inferior to those in allophanic Andisol. This is attributed to insufficient uptake of nitrogen due to poor rooting in the acid subsoils of non-allophanic Andisol.4) The distribution map of allophanic and non-allophanic Andisols in Tohoku district was completed. According to this map, nonallophanic Andisol was located in high rainfall region, whereas allophanic Andisols was seen in relatively low rainfall region and/or regions abundant in mafic glass or pumis.